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POSSIBLY EFFECTIVE

• Anxiety. Small clinical studies suggest that oral ashwagandha might reduce anxiety. Details: A meta-analysis of small randomized controlled trials in adults with anxiety and/or insomnia shows that taking ashwagandha 600-12,000 mg orally daily for 6-10 weeks moderately improves anxiety scores when compared with placebo. However, the validity of this study is limited by high heterogeneity (114787). One small clinical study in postal workers reporting moderate or severe anxiety shows that taking ashwagandha root (Swiss Herbals) 300 mg twice daily for 12 weeks, in combination with standard psychotherapy interventions, including dietary counseling, deep breathing exercise instruction, and a multivitamin, reduces anxiety scores when compared with standard psychotherapy interventions and placebo (19271). Additionally, two small clinical studies in adults with mild to moderate anxiety, depression, or stress show that taking a specific ashwagandha root extract standardized to contain 2.5% withanolides (Shagandha, Sabinsa Corp.) 500 mg with piperine 5 mg daily for 60-90 days reduces anxiety symptoms and perceived stress and improves sleep and quality of life when compared with placebo (113608,113609). However, another clinical study in young adults shows that taking a specific ashwagandha root and leaf extract (NooGandha, Specnova LLC) 225 mg or 400 mg daily for 30 days does not improve anxiety, stress, and depression scores when compared with placebo (107370).
• Generalized anxiety disorder (GAD). Oral ashwagandha may modestly improve symptoms of anxiety in patients with GAD. Details: Clinical practice guidelines from the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) provisionally recommend ashwagandha root extract at doses of 300-600 mg, standardized to 5% withanolides, daily as monotherapy or adjunctive therapy in patients with GAD. This recommendation is based on a review of three preliminary clinical trials with consistent results (110318). Two of these studies are described below. A small clinical trial in patients with GAD who are taking selective serotonin reuptake inhibitors (SSRIs) shows that taking ashwagandha 1 gram daily for 6 weeks reduces symptoms of anxiety by 48%, compared with a 27% reduction in patients taking placebo. Furthermore, by the end of treatment, 72% of patients taking ashwagandha were determined to have mild symptoms of GAD, compared with only 32% of those taking placebo (102687). Another preliminary clinical trial in patients aged 16 years and older with GAD shows that taking ashwagandha root powder granules 4 grams three times daily for 60 days moderately improves anxious mood in 58% of patients, compared with no moderate improvement in the placebo group. Mild improvement occurred in 82% of patients in the placebo group and 40% of patients in the ashwagandha group (90654). Another small clinical trial in adults with general anxiety disorder shows that taking ashwagandha, standardized to 35% withanolides, 60-120 mg orally daily for 60 days improves anxiety scores by about 60% when compared with placebo (114792).
• Insomnia. Oral ashwagandha may modestly improve sleep in patients with insomnia or non-restorative sleep. Details: A small meta-analysis in patients with insomnia and healthy patients shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 250-600 mg daily or a specific root and leaf extract (Shoden, Arjuna Natural) 120 mg daily for 6-12 weeks modestly improves overall sleep, as well as sleep quality, sleep latency, total sleep time, wake time after sleep onset, and sleep efficiency, when compared with placebo. Effects were more pronounced in those with insomnia, with doses of at least 600 mg daily, and with treatment durations of at least 8 weeks (106784). These findings may be limited by heterogeneity of the included studies. A meta-analysis of 2 small randomized controlled trials in adults with anxiety and/or insomnia shows that taking ashwagandha 600 mg orally daily for 8-10 weeks modestly improves sleep onset latency, total sleep time, sleep efficiency, and sleep quality scores, but not wake after sleep onset or total time in bed, when compared with placebo. However, the validity of this study is limited by moderate heterogeneity (114787). In patients with non-restorative sleep, clinical research shows that taking a specific ashwagandha extract (Shoden, Arjuna Natural Private Ltd) 125 mg daily for 6 weeks increases sleep quality by 72%, compared with an improvement of 29% in patients taking placebo. Small to moderate improvements also occurred in total sleep time, sleep latency, and number of times awake (103476). Ashwagandha has also been evaluated as part of a combination treatment. A very small clinical trial in adults with poor quality sleep shows that taking milk fortified with ashwagandha 250-600 mg, or ashwagandha 250 mg and tryptophan, orally daily for 90 days moderately improves sleep quality scores when compared with placebo (114791). Additional data are needed to determine if the addition of tryptophan improves results more than ashwagandha alone.
• Stress. Oral ashwagandha seems to help reduce stress and may also reduce stress-related weight gain. Details: A meta-analysis of seven small clinical studies in healthy adults, patients with chronic stress, or patients with psychiatric conditions shows that taking ashwagandha 240-1000 mg daily for 8-12 weeks improves stress when compared with placebo (109587). Clinical studies, some of which are included in the meta-analysis mentioned above, evaluating adults with chronic stress show that taking specific ashwagandha root extracts 240 mg daily (Shoden, Arjuna Natural Ltd.), 300 mg twice daily (KSM-66, Ixoreal Biomed), or 500 mg daily (Shagandha, Sabinsa Corp.) with piperine 5 mg for 60 days, or a specific slow-release capsule containing ashwagandha root extract (Prolanza) 300 mg daily for 90 days reduces perceived stress and cortisol levels when compared with baseline and placebo (90652,95617,101816,102682,107371,113608). Additionally, a small clinical study in adults with stress and a related comorbidity, such as anxiety or depression, shows that taking ashwagandha root and leaf extract (Sensoril, Kerry Group) 125-500 mg orally daily for 8 weeks improves stress scores in a dose-dependent manner when compared with placebo (114112). In contrast, a moderate-sized study in adults with overweight or mild obesity with moderate-to-high levels of stress and fatigue shows that taking ashwagandha root extract (Witholytin, Verdure Sciences Inc) 200 mg twice daily for 12 weeks reduces stress when compared to baseline, but not when compared with placebo (113611).In healthy college students, clinical research also shows that taking ashwagandha root extract 350 mg twice daily for 30 days improves qualitative perceptions of stress management, but not stress scores, when compared with placebo (109589,109590). Other clinical research shows that taking ashwagandha root extract 500 mg twice daily may prevent stress-related weight gain when compared with placebo (95617).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging. A small clinical study suggests that oral ashwagandha may modestly improve well-being, sleep, and alertness in elderly patients. Details: A small clinical trial in individuals aged 65-80 years shows that taking ashwagandha root extract (KSM-66, Ixoreal Biomed) 600 mg daily for 12 weeks improves overall well-being, sleep quality, and mental alertness by small to moderate amounts when compared with placebo (102684).
• Androgenic alopecia. It is unclear if topical ashwagandha is beneficial for androgenic alopecia. Details: A small clinical study in adults with mild to moderate hair loss, including androgenic alopecia, shows that applying ashwagandha root extract serum (KSM-66, Ixoreal Biomed) 1-2 drops to the scalp daily for 75 days reduces hair shedding and increases hair density, growth, and thickness when compared with placebo (113613).
• Antipsychotic-induced metabolic side effects. It is unclear if ashwagandha is beneficial for attenuating the metabolic side effects of antipsychotic agents. Details: One preliminary clinical trial shows that taking a specific ashwagandha extract (Cap Strelaxin, M/s Pharmanza Herbal Pvt. Ltd.) 400 mg three times daily for one month reduces serum triglycerides by 12% and fasting blood glucose by 15% when compared with baseline levels. Patients were taking atypical antipsychotics and had modestly elevated triglycerides and fasting blood glucose levels at baseline (90649). The validity of these findings is limited by the lack of a comparator group.
• Asthma. Although there has been interest in using oral ashwagandha for asthma, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Athletic performance. It is unclear if ashwagandha is beneficial for improving athletic performance. Details: A meta-analysis of four small clinical trials shows that taking ashwagandha increases aerobic capacity in athletes and non-athletes based on the measurement of maximum oxygen consumption. Effective doses ranged from 500-1000 mg daily for up to 12 weeks (102683). Another meta-analysis shows that taking ashwagandha in doses of 120-1250 mg daily, as a single dose or divided twice daily, for up to 6 months seems to improve muscle strength, speed, time to exhaustion, recovery time, and cardiorespiratory fitness in athletes and non-athletes (105824). However, the validity of this analysis is reduced by the lack of a control group, the varied training levels of the subjects, and the wide range of outcomes assessed. A moderate-sized clinical trial in active adults shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg orally twice daily, in addition to resistance training, for 8 weeks improves the maximum rate of oxygen consumption (VO2 max) as a measure of cardiorespiratory endurance, but not muscle strength when compared with placebo (114788). More research is needed to determine whether taking ashwagandha can improve athletic performance.
• Attention deficit-hyperactivity disorder (ADHD). Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In a preliminary clinical trial, children with ADHD were given a combination herbal extract formula (Nurture & Clarity), containing ashwagandha, white peony root, gotu kola, blue-green algae, bacopa, and sage, 3 mL three times daily for 4 months. Measures of attention, cognition, and impulse control improved significantly in children receiving ashwagandha when compared with placebo (19272). The dose of ashwagandha in the combination product was not reported, and the effect of ashwagandha alone in ADHD is unclear. Back pain.Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in adults with back pain shows that taking a specific combination product (Berelief, Monteloeder S.L.) containing ashwagandha 66%, rosemary, and sesame seed, 200-400 mg orally daily for 12 weeks moderately improves pain scores and reduces the need for adjunct pain medication when compared with placebo (114793). It is unclear if this effect is due to ashwagandha, other ingredients, or the combination.
• Bipolar disorder. It is unclear if oral ashwagandha is beneficial for improving cognitive function in adults with bipolar disorder. Details: Clinical research shows that taking ashwagandha extract (Sensoril, Natreon, Inc.) 250 mg daily for 1 week and then 250 mg twice daily for 7 weeks, improves some, but not all, measures of cognition by a small-to-moderate amount when compared with placebo (90653).
• Bronchitis. Although there has been interest in using oral ashwagandha for bronchitis, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Cerebellar ataxia. It is unclear if oral ashwagandha is beneficial for improving balance in patients with cerebellar ataxia. Details: A small, open-label study evaluating ashwagandha 500 mg three times daily in combination with Ayurvedic therapy for one month showed improvement in balance indices in subjects with cerebellar ataxia when compared with baseline (19273). The validity of this finding is limited by the lack of a comparator group. Additionally, it is unclear if this effect is due to ashwagandha, other ingredients, or the combination.
• Chemotherapy-related fatigue. Evidence is limited to one small clinical study in patients with breast cancer. Details: In preliminary clinical research in patients with breast cancer, taking ashwagandha powdered root extract 2 grams (Himalaya Drug Co) three times daily through six cycles of chemotherapy decreases chemotherapy-related fatigue when compared with no treatment. Fatigue scores were 16% to 52% higher in the control group when compared to the ashwagandha group (90651).
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral ashwagandha is beneficial in patients with COPD. Details: A small clinical study in patients with stable COPD shows that taking ashwagandha root extract 250 mg twice daily for 12 weeks, along with conventional therapy, improves measures of lung function and exercise tolerance, but not quality of life, when compared with conventional therapy alone (109588).
• Cognitive function. Although there has been interest in using oral ashwagandha for cognitive function, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Constipation. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults with constipation shows that taking a combination product containing ashwagandha root and ambrette fruit extracts 300 mg or 500 mg daily for 14 days improves bowel movement frequency and abdominal, rectal, and stool symptoms when compared with placebo (112114). Additionally, a moderate-sized clinical study in adults with functional constipation shows that using the same combination of ashwagandha and ambrette 300 mg or 500 mg daily for 60 days moderately improves constipation symptom scores and bowel movement scores when compared with placebo (114115). It is unclear if these effects are due to ashwagandha, ambrette, or the combination.
• Coronavirus disease 2019 (COVID-19). Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults hospitalized with COVID-19 shows that taking a specific combination product, (Artovid-20, Bioved Pharmaceuticals) containing ashwagandha, ginger, turmeric, and Boswellia, 1,776 mg orally twice daily for 14 days shortens the duration of symptoms by 0.9 days when compared with placebo. Taking the combination product also modestly reduced the severity ratings of some symptoms, such as sore throat and cough, however, these improvements are unlikely to be clinically relevant (109899). Another small clinical study in adults with mild to moderate COVID-19 shows that taking ashwagandha 500 mg and ginger 1000 mg twice daily for 15 days reduces time to recovery by around 6 days and increases the rate of clinical cure 14-fold and 2.6-fold at days 5 and 7, respectively, when compared with a control. However, taking this combination does not appear to improve the proportion of patients with a negative COVID-19 test, viral clearance, serum antibodies, chest findings, or disease progression when compared with control (112094). The validity of these findings is limited by a lack of blinding, and the study may have been inadequately powered to detect a difference between groups. Other clinical research in adults hospitalized with mild to moderate COVID-19 shows that taking a specific combination product (Coroprotect) containing ashwagandha, pomegranate, turmeric, bacopa, licorice, and other ingredients, twice daily for 10 days improved cough, breathlessness, and fatigue symptoms when compared with placebo (114114). It is unclear if any effects are due to ashwagandha, other ingredients, or the combination.
• Depression. It is unclear if oral ashwagandha is beneficial for depression. Details: A small clinical study in adults with mild to moderate depression, anxiety, or stress shows that taking a specific ashwagandha root extract standardized to contain 2.5% withanolides (Shagandha, Sabinsa) 500 mg with piperine 5 mg daily for 90 days reduces the severity of depressive symptoms, improves sleep and quality of life, and increases serum serotonin levels when compared with placebo (113609).
• Diabetes. It is unclear if oral ashwagandha is beneficial for type 2 diabetes. Details: In patients with type 2 diabetes, preliminary clinical research shows that ashwagandha 3 grams daily for 30 days decreases blood glucose to a degree similar to oral hypoglycemic drugs (19274). However, this study did not compare ashwagandha directly to a group taking oral hypoglycemic drugs.
• Fatigue. It is unclear if oral ashwagandha is beneficial for fatigue. Details: A moderate-sized clinical study in adults with overweight or obesity and moderate-to-high levels of fatigue and stress shows that taking ashwagandha root extract (Witholytin, Verdure Sciences Inc.) 200 mg twice daily for 12 weeks reduces self-reported fatigue when compared with placebo (113611).
• Fibromyalgia. Although there has been interest in using oral ashwagandha for fibromyalgia, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Hiccups. Although there has been interest in using oral ashwagandha for hiccups, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Hypercholesterolemia. It is unclear if ashwagandha is beneficial for hypercholesterolemia. Details: A very small clinical study in subjects with hypercholesterolemia shows that ashwagandha 3 grams daily for 30 days decreases serum cholesterol, triglyceride, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) cholesterol levels when compared with baseline (19274). The validity of these findings is limited by the lack of a comparator group.
• Hypothyroidism. It is unclear if ashwagandha is beneficial for hypothyroidism. Details: Preliminary clinical research in adults with subclinical hypothyroidism shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily for 8 weeks increases triiodothyronine (T3) and thyroxine (T4) levels by 42% and 20%, respectively, and reduces serum TSH levels by 17% from baseline. These changes are significant when compared with placebo (97292). However, the effects of ashwagandha on thyroid hormone levels in patients with overt hypothyroidism, or in patients taking prescription thyroid hormones, is unknown.
• Infertility. Although there has been interest in using oral ashwagandha for infertility in females, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Male infertility. It is unclear if oral ashwagandha is beneficial for male infertility. Details: Preliminary clinical research in males with infertility shows that taking ashwagandha root powder for approximately 3 months modestly improves hormone levels, as well as sperm count and motility, when compared with baseline (19275,90650). The validity of these findings is limited by the lack of a comparator group. One study used a specific ashwagandha root extract (KSM-66 Ashwagandha, Ixoreal Biomed) 225 mg three times daily; another study provided doses of 5 grams daily (19275,90650).
• Menopausal symptoms. Oral ashwagandha may be beneficial for menopausal symptoms. Details: A small clinical study in healthy adults in perimenopause shows that taking a specific ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily for 8 weeks improves menopausal symptom severity by 24%, compared with 11% in those receiving placebo. Quality of life and hot flashes also were improved in those taking ashwagandha (106785).
• Obsessive-compulsive disorder (OCD). It is unclear if ashwagandha is beneficial for OCD. Details: Preliminary clinical research shows that taking ashwagandha root extract 120 mg after meals for 6 weeks, in conjunction with prescribed selective-serotonin reuptake inhibitors (SSRIs), might reduce OCD symptom severity when compared with prescribed SSRIs alone. The dose was initiated at 30 mg daily and increased by 30 mg every 4 days. Although OCD scores were significantly reduced when compared with placebo, it should be noted that scores were already significantly lower in the placebo group at baseline (95618).
• Osteoarthritis. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In patients with osteoarthritis, taking a specific combination supplement, containing ashwagandha 450 mg, Ayurvedic zinc complex 50 mg, guggul 100 mg, and turmeric 50 mg (Articulin-F) two capsules three times daily for 3 months reduces symptoms of pain and swelling when compared with placebo. However, there were no radiological improvements (19276). It is unclear if this effect is due to ashwagandha, other ingredients, or the combination.
• Parkinson disease. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: In patients with Parkinson disease, a small clinical study shows that taking a product containing ashwagandha 14.5 grams, cowhage 4.5 grams, Hyoscyamus reticulantus 0.75 grams, and Sida cordifolia 14.5 grams in lukewarm milk twice daily for 56 days improves symptoms like tremor, stiffness, and cramps when compared with baseline. The therapy followed 28 days of cleansing or eliminative therapy using Ayurvedic remedies (6899). The validity of these findings is limited by the lack of a comparator group. Also, it is unclear if these effects are due to ashwagandha, other ingredients, or the combination. Cowhage contains levodopa, which may contribute to any benefit seen with this combination product.
• Psychological well-being. It is unclear if oral ashwagandha is beneficial for improving psychological well-being in college students. Details: A small clinical study in healthy college students shows that taking ashwagandha root extract 350 mg twice daily for 30 days improves perceptions of well-being, including improvements in energy, mental clarity, food cravings, and sleep quality, when compared with placebo. Qualitative analysis also suggests these students had improvements in stress management, but stress scores were not reduced when compared with placebo (109589,109590).
• Rheumatoid arthritis (RA). It is unclear if oral ashwagandha is beneficial for improving symptoms of RA. Details: Preliminary clinical research shows that taking ashwagandha powder 5 grams twice daily for 3 weeks, followed by 4 weeks of sidh makardhwaj (a mixture of gold, mercury, and sulfur) 100 mg with honey daily, modestly improves symptoms in about 50% of males and 60% of females with RA when compared with baseline (95620). The lack of a control group limits the validity of this finding. Additionally, the effect of ashwagandha powder alone is unclear. Another small study in adults with RA shows that taking a combination product containing ashwagandha, ginger, black pepper, and colchicum luteum orally twice daily for 4 weeks does not improve RA disease scores when compared with celecoxib 100 mg orally twice daily (114785). However, the interpretation of these results is limited by poor methodology, and the study may have been inadequately powered to detect a difference between groups.
• Sexual dysfunction. Small clinical studies suggest that oral ashwagandha root extract may help improve sexual arousal and sexual desire in some females and males with sexual dysfunction. Details: Two, small clinical studies in adult females with sexual dysfunction show that taking ashwagandha root extract (KSM-66, Ixoreal Biomed) 300 mg twice daily with food for 8 weeks in conjunction with or without counseling increases the number of successful sexual encounters and improves orgasms, satisfaction, lubrication, and arousal when compared with placebo or counseling alone (95619,110492). Also, a small clinical study in adult males with low sexual desire shows that taking the same ashwagandha root extract 300 mg twice daily after meals for 8 weeks improves subjective sexual functioning scores, including measures of sexual arousal, sexual desire, sexual behavior, and orgasm, when compared with placebo (109586).
• Smoking cessation. Oral ashwagandha has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in adults with a history of smoking 5 or more cigarettes daily for at least 3 years shows that taking a specific combination product containing ashwagandha 100 mg, Indian gooseberry, tribulus, bacopa, Albizia lebbeck, licorice, clove, ginger, cowhage, holy basil, and turmeric (Smotect, Smotect India) daily for 3 months reduces the number of cigarettes smoked daily and levels of alveolar carbon monoxide and carboxyhemoglobin but does not improve lung capacity when compared with placebo (112115). It is unclear if these effects are due to ashwagandha, other ingredients, or the combination.
• Tuberculosis. Although there has been interest in using oral ashwagandha for tuberculosis, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Vitiligo. Although there has been interest in using oral ashwagandha for vitiligo, there is insufficient reliable information about the clinical effects of ashwagandha for this condition.
• Wrinkled skin. It is unclear if topical ashwagandha is beneficial in individuals with wrinkled skin. Details: A small clinical study in healthy adults with photoaged skin shows that applying ashwagandha root extract 8% lotion daily for 60 days improves physician-rated scores for skin wrinkles, hydration, brightness, tone, and pigmentation and improves other measures of skin elasticity and hydration when compared with placebo. However, changes in melanin content did not differ between treatment groups (111538).
• Wound healing. Although there has been interest in using topical ashwagandha for healing of skin ulcers and skin sores, there is insufficient reliable information about the clinical effects of ashwagandha for this condition. More evidence is needed to rate ashwagandha for these uses.

(Read more about ASHWAGANDHA)

POSSIBLY EFFECTIVE

• Schizophrenia. Oral glycine may improve negative, but not positive, symptoms of schizophrenia when used as adjunct to therapy with typical antipsychotics in patients resistant to monotherapy. However, glycine does not seem to provide additional benefit when used with clozapine. Details: Some small clinical trials show that taking glycine 0.4-0.8 grams/kg daily in divided doses along with conventional treatment seems to reduce negative symptoms of schizophrenia in patients that are resistant to monotherapy with typical antipsychotics such as thioridazine, haloperidol, and perphenazine (10250,10251,10252,98591). However, when used with the atypical antipsychotic clozapine, glycine appears to have a negligible effect on or worsen symptoms of schizophrenia (10253,11321). Additionally, glycine does not seem to improve positive symptoms of schizophrenia (10250,10251,10252,98591).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• 3-phosphoglycerate dehydrogenase (3-PGDH) deficiency. It is unclear if oral glycine is beneficial in patients with 3-PGDH deficiency. Details: A case series describing two patients with 3-PGDH deficiency who did not respond to serine supplementation suggests that taking oral glycine 0.2 grams/kg daily along with serine might reduce seizure frequency. 3-PGDH deficiency is a rare condition in which serine is not synthesized properly (10254).
• Aging. Oral glycine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults aged 61-80 years with overweight or obesity shows that taking a specific combination product (GlyNAC), providing glycine 100 mg/kg and N-acetyl cysteine 100 mg/kg, daily for 16 weeks improves some markers associated with aging, including glutathione levels, oxidative stress, mitochondrial impairment, genomic damage, inflammation, and endothelial dysfunction, when compared to baseline. Improvements in these measures were lacking in the placebo group (110624). The validity of these findings is limited by a lack of statistical comparison between groups. Also, it is unclear if these effects are due to glycine, N-acetyl cysteine, or the combination.
• Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral glycine for ADHD, there is insufficient reliable information about the clinical effects of glycine for this purpose.
• Benign prostatic hyperplasia (BPH). Although there has been interest in using oral glycine for BPH, there is insufficient reliable information about the clinical effects of glycine for this purpose.
• Cognitive function. Small clinical studies suggest that oral glycine may modestly improve memory and cognitive function in some patients. Details: Two small clinical studies in healthy young adults and adults with psychosis risk syndrome show that taking glycine 0.2-0.4 grams/kg once or twice daily for up to 24 weeks may improve some measures of memory and cognitive performance when compared with baseline or placebo (11322,92321).
• Cystic fibrosis. It is unclear if oral glycine is beneficial in patients with cystic fibrosis. Details: A small clinical trial in patients 6-23 years of age with cystic fibrosis shows that taking glycine 0.5 grams/kg daily for 8 weeks modestly improves some measures of lung function and reduces sputum and dyspnea by 15% and 23%, respectively, when compared with placebo. However, taking glycine does not improve appetite or energy (98583).
• Gout. Oral glycine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with mild hyperuricemia shows that taking a powder containing glycine 3 grams and L-tryptophan 0.2 grams nightly at bedtime for 6 weeks reduces serum uric acid levels by 0.3 mg/dL when compared with placebo. Improvements also occurred in the subgroup of patients with uric acid levels greater than 7 mg/dL, the point at which symptoms of gout can occur (99883). However, it is unclear if this combination improves gout-related pain. Also, it is not clear if these findings are due to glycine, L-tryptophan, or the combination.
• Insomnia. Small clinical studies suggest that oral glycine may modestly improve sleep quality and daytime feelings of fatigue in patients with poor sleep quality or a restricted sleep duration. Details: Two very small studies in patients who have reported a subjective reduction in sleep quality show that taking glycine 3 grams one hour before bedtime for 2-4 days improves overall sleep quality and sleep efficacy when compared with placebo (92318,92320). Another very small clinical study in healthy males shows that taking glycine 3 grams 30 minutes before bedtime for 3 nights, during which time sleep duration is restricted by 25%, modestly reduces feelings of fatigue after the first night, but not after the third night, when compared with placebo (92316). The effects of glycine on sleep measures have also been evaluated in combination with other ingredients. A very small crossover study in healthy adults without documented sleep disorders shows that taking a combination product containing glycine 3000 mg, tryptophan 1000 mg, magnesium 300 mg, tart cherry powder 220 mg, and L-theanine 200 mg before bed for 3 nights reduces sleep onset latency, increases total sleep time, increases sleep efficiency, and reduces morning sleepiness when compared with placebo (111184). It is unclear if these effects are due to glycine, other ingredients, or the combination.
• Isovaleric acidemia. Although there has been interest in using oral glycine for isovaleric acidemia, there is insufficient reliable information about the clinical effects of glycine for this purpose.
• Metabolic syndrome. Although there has been interest in using oral glycine for metabolic syndrome, there is insufficient reliable information about the clinical effects of glycine for this purpose.
• Obesity. Oral glycine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults aged 61-80 years with overweight or obesity shows that taking a specific combination product (GlyNAC), providing glycine 100 mg/kg and N-acetyl cysteine 100 mg/kg, daily for 16 weeks reduces waist circumference but does not improve body weight or body mass index (BMI) when compared to baseline. None of these outcomes were improved in individuals taking placebo (110624). The validity of these findings is limited by a lack of statistical comparison between groups. Also, it is unclear if these effects are due to glycine, N-acetyl cysteine, or the combination.
• Overactive bladder. It is unclear if oral glycine is beneficial in patients with overactive bladder. Details: One very small, non-randomized, crossover trial in patients with overactive bladder shows that taking glycine 3 grams twice daily for 4 weeks reduces urinary urgency, urinary incontinence, and nighttime urinary frequency and improves quality of life scores when compared with placebo (106497). The validity of these findings is limited by a lack of randomization.
• Physical performance. Oral glycine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A very small clinical study in adults aged 61-80 years with overweight or obesity shows that taking a specific combination product (GlyNAC), providing glycine 100 mg/kg and N-acetyl cysteine 100 mg/kg, daily for 16 weeks improves upper and lower extremity strength and gait speed, but not walking distance, when compared to baseline. None of these outcomes were improved in individuals taking placebo (110624). The validity of these findings is limited by a lack of statistical comparison between groups. Also, it is unclear if these effects are due to glycine, N-acetyl cysteine, or the combination.
• Stroke. It is unclear if sublingual glycine is beneficial in patients with acute ischemic stroke. Details: One small clinical study in patients with acute ischemic stroke in the carotid artery territory shows that taking glycine 1-2 grams sublingually daily for 5 days, starting within 6 hours after the onset of stroke, modestly improves clinical outcomes on the Orgogozo Stroke Scale, the Scandinavian Stroke Scale, and the Barthel index when compared with placebo (11320).
• Venous leg ulcers. Topical glycine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that applying a cream containing glycine, L-cysteine, and DL-threonine to leg ulcers reduces pain and modestly improves healing when compared with a placebo cream (10255). It is unclear if these effects are due to glycine, other ingredients, or the combination.
• Wound healing. Although there has been interest in using topical glycine for wound healing, there is insufficient reliable information about the clinical effects of glycine for this purpose. More evidence is needed to rate glycine for these uses.

(Read more about GLYCINE)

POSSIBLY EFFECTIVE

• Metabolic syndrome. Oral inositol seems to modestly improve lipid parameters, blood pressure, and insulin resistance in patients with metabolic syndrome. Details: Some clinical research in postmenopausal adults with metabolic syndrome following a low-calorie diet shows that taking myo-inositol 2 grams twice daily for one year reduces total cholesterol by 29 mg/dL, triglycerides by 64 mg/dL, systolic and diastolic blood pressure by 9 mmHg and 6 mmHg, respectively, increases high-density lipoprotein (HDL) cholesterol by 6 mg/dL, and improves insulin resistance when compared with placebo. It did not reduce body mass index or waist circumference in these patients (91554). A meta-analysis of clinical studies in a mixed population shows similar effects on blood pressure, especially among postmenopausal adults with metabolic syndrome, at durations exceeding 8 weeks, and at doses of at least 4 grams (108820). Another clinical study in postmenopausal adults with metabolic syndrome and at risk for breast cancer shows that taking a combination of inositol and alpha-lipoic acid daily for 6 months, in combination with a low-calorie diet, reduces insulin resistance (HOMA-IR) by at least 20% when compared with a low-calorie diet alone. Also, taking inositol and alpha-lipoic acid seems to increase HDL cholesterol by about 6% and reduce triglycerides by 5% when compared to baseline (91543). It is unclear if these effects are due to inositol, alpha-lipoic acid, or the combination.
• Polycystic ovary syndrome (PCOS). Oral inositol, often in combination with folic acid, seems to improve some glycemic, lipid, metabolic, hormonal, and reproductive parameters in patients with PCOS. However, research is conflicting. Details: Oral inositol, most frequently in the forms of myo-inositol or D-chiro-inositol, has been evaluated for efficacy in a wide range of outcomes associated with PCOS including reproductive and pregnancy outcomes, metabolic parameters, and anthropomorphic measures. Often, inositol is taken in combination with folic acid or metformin. Inositol has been investigated for its effect on metabolic parameters that are often altered in PCOS. A meta-analysis of 9 studies in patients with PCOS shows that taking myo-inositol or D-chiro-inositol with or without folic acid marginally decreases body mass index (BMI) by about 0.5 kg/m2 when compared with placebo (111670). Inositol has also been evaluated for its effect on glucose metabolism in adults with PCOS. Meta-analyses of about 10 studies show that taking myo-inositol or D-chiro-inositol with or without folic acid reduces fasting plasma glucose by 1-4 mg/dL (98944,111670). However, evidence is conflicting on the effect of inositol on insulin levels and measures of insulin resistance (98944,111670). Additionally, most studies show that inositol does not improve measures of glucose metabolism more than metformin. The effect of inositol on lipid profiles has also been studied. A meta-analysis of 2 clinical studies and other small clinical studies show that taking inositol as D-chiro-inositol with or without folic acid modestly reduces total cholesterol and triglycerides when compared with control (2028,98944,91552). Some studies have also investigated the effect of inositol on hormone levels. Meta-analyses show that inositol modulates androgen levels as shown by reduced total and free testosterone, androstenedione, and increased sex-hormone binding globulin when compared with placebo. (2028,91552,98944,111670). The validity of these effects is limited by high heterogeneity in terms of inclusion and exclusion criteria, dose, and treatment duration within the included studies. Myo-inositol has also been compared with metformin in some clinical research, with some evidence of benefit (95085,95086). Meta-analyses of small clinical studies show that taking myo-inositol 2-4 grams daily, with or without folic acid, for 12-24 weeks does not improve fasting blood glucose, fasting insulin, insulin resistance (HOMA-IR), BMI, waist-hip circumference, or androgen levels when compared with metformin 1.5-2.5 grams daily (100705,108823,111670,111670). However, inositol seems to have a lower risk of adverse effects than metformin. These analyses are limited due to the small size, methodological issues, and high heterogeneity of the included studies. In combination with metformin, small clinical studies show that taking metformin, myo-inositol 550 mg, and D-chiro-inositol 150 mg twice daily is associated with improved lipid parameters and postprandial insulin levels when compared with metformin alone (108822). Meta-analyses and clinical studies have investigated the effect of inositol on ovulation, reproduction, and pregnancy outcomes. Some research suggests that inositol increases ovulation rate, promotes cycle normalization, and improves ovarian function in patients with PCOS (2028,91552,98944,111670). A small clinical study shows that taking myo-inositol 4 grams and folic acid 400 mcg (Inofolic, Lo.Li.Pharma) daily for three spontaneous cycles induces ovulation in about 62% of individuals with anovulatory PCOS and insulin resistance. Adding clomiphene citrate with myo-inositol induces ovulation in about 72% of the patients who remain anovulatory after treatment with myo-inositol alone (91547). Another clinical study shows that taking a combination of inositol 2 grams, folic acid 200 mcg, and N-acetyl cysteine 600 mg (Ovaric HP, Just Pharma) twice daily for 12 months improves ovulation rates in PCOS patients with oligomenorrhea, regardless of insulin sensitivity at baseline (91553). Despite evidence that inositol improves ovulation rates, it does not appear to impact pregnancy rates (111670). Some research has also investigated the effects of taking both isomers of inositol concomitantly. Taking myo-inositol 550 mg plus D-chiro-inositol 13.8 mg (Inofolic Combi, Lo.Li.Pharma) twice daily, beginning 12 weeks before ovarian hyperstimulation and continuing throughout pregnancy, improves oocyte quality when compared to treatment with D-chiro-inositol alone. The combination appears to increase fertilization rate in patients aged 35 years or younger, but not those older than 35 years (91544). Other clinical research shows that taking myo-inositol 550 mg and D-chiro-inositol 150 mg twice daily for 12 weeks improves pregnancy rates and live birth rates by an additional 10% and 11%, respectively, when compared with myo-inositol 550 mg plus D-chiro-inositol 13.8 mg. The higher-dose combination also resulted in a 15% lower rate of ovarian hyperstimulation syndrome when compared with those taking the lower dose of D-chiro-inositol (102317). Lastly, other research shows that taking myo-inositol and D-chiro-inositol together may improve metabolic parameters faster than taking myo-inositol alone (91550). Research has also evaluated the effects of inositol on other pertinent clinical outcomes in PCOS. Several small clinical studies show that taking the combination of myo-inositol and D-chiro-inositol, alone or in combination with metformin, improves menstrual cycle irregularity when compared with metformin alone, but not as much as a taking a combined hormonal contraceptive (108822,108824). The validity of these findings is limited by the unblinded nature of the studies. Also, a small clinical study shows that taking metformin with myo-inositol 550 mg and D-chiro-inositol 150 mg twice daily is associated with improved acne, but not hirsutism, at 6 months, when compared with metformin alone (108822). The validity of these findings is limited by the unblinded nature of the study. More research is needed to clarify the effect of inositol on anthropometric, metabolic, and endocrine outcomes in patients with PCOS.
• Preterm labor. Oral inositol in combination with folic acid seems to prevent preterm labor in individuals at risk for gestational diabetes. Details: A meta-analysis of five clinical trials in individuals at risk for gestational diabetes shows that taking myo-inositol plus folic acid daily, beginning during the first trimester and continuing throughout pregnancy, decreases the risk of preterm delivery by 64% when compared with folic acid alone. Patients in all but one study included in this analysis took myo-inositol 2 grams plus folic acid 200 mcg twice daily, while patients in the other study took myo-inositol 1100 mg plus D-chiro-inositol 27.6 mg and folic acid 400 mcg daily (100706). It's unclear if these results are generalizable to individuals with a low risk for gestational diabetes.

POSSIBLY INEFFECTIVE

• Acute respiratory distress syndrome (ARDS). Oral or intravenous inositol does not seem to prevent ARDS in preterm infants and may be associated with worsened outcomes. Details: Historically, small clinical trials in infants with or at risk for ARDS have suggested that myo-inositol, given parenterally and enterally for 5-10 days, might improve survival and reduce the risk of death and serious complications (2191,2192,91546). However, a large, high-quality clinical study in infants born at less than 28 weeks' gestation at risk for ARDS shows that myo-inositol 40 mg/kg given intravenously and then enterally every 12 hours for up to 70 days does not reduce the risk of death or retinopathy of prematurity (ROP). In fact, the rate of death or type 1 ROP increased by 7% in the myo-inositol group when compared to the control group, and a higher incidence of adverse events in the myo-inositol group, including poor perfusion, hypotension, and infections, led to early trial discontinuation (98946). Long-term follow-up until 24 months corrected age confirms that the initial increase in mortality rate in the myo-inositol group remained stable; however, there was no difference in a composite outcome of death or survival with moderate or severe neurodevelopmental impairment, as well as no difference in the risk of ROP, between the treatment and control groups (108819). The most recent meta-analysis, which incorporates this large clinical study, concludes that inositol supplementation does not reduce the risk of death in infants at risk for ARDS (102319).
• Anxiety. Oral inositol does not seem to be beneficial for patients with anxiety. Details: A meta-analysis of four clinical trials shows that taking inositol orally does not improve anxiety severity in patients with anxiety disorders, including obsessive-compulsive disorder, panic disorder, or post-traumatic stress disorder, when compared with placebo (91549).
• Depression. Oral inositol does not seem to be beneficial for patients with depression. Details: Guidelines from the World Federation of Societies of Biological Psychiatry (WFSBP) and Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce state that inositol in doses up to 12 grams daily is not currently recommended as monotherapy or adjunctive use for major depressive disorder due to a lack of evidence for efficacy (110318). Additionally, a meta-analysis of seven clinical trials shows that inositol does not significantly improve symptoms of depression in patients with bipolar depression, major depressive disorder, or premenstrual dysphoric disorder (PMDD) (91549). While limited research shows that patients receiving inositol for 4 weeks may improve, patients initially responding to inositol seem to relapse rapidly upon discontinuation of treatment (2026,2185). Additionally, taking inositol with a selective serotonin reuptake inhibitor (SSRI) doesn't appear to improve the effectiveness of SSRI therapy or improve depression in SSRI treatment failures (2025,10851).
• Diabetic neuropathy. Oral inositol does not seem to be beneficial for patients with diabetic neuropathy. Details: Most preliminary clinical research shows that taking inositol orally doesn't improve the symptoms of diabetic neuropathy (2193,2194,2195).
• Retinopathy of prematurity. Oral or intravenous inositol does not seem to prevent retinopathy of prematurity (ROP) in preterm infants. Details: A meta-analysis of six clinical trials shows that myo-inositol, given parenterally and/or enterally, does not seem to reduce the risk of ROP when compared with placebo in preterm infants (100704). A large, high-quality clinical study included in this meta-analysis shows that myo-inositol 40 mg/kg given intravenously and then enterally every 12 hours for up to 70 days does not reduce the risk of death or ROP in infants born at less than 28 weeks' gestation. In fact, the rate of death or type 1 ROP increased by 7% in the myo-inositol group when compared with placebo and a higher incidence of adverse events in the myo-inositol group, including poor perfusion, hypotension, and infections, led to early trial discontinuation (98946). Long-term follow-up until 24 months corrected age confirms that the initial increase in mortality rate in the myo-inositol group remained stable; however, there was no difference in a composite outcome of death or survival with moderate or severe neurodevelopmental impairment, as well as no difference in the risk of ROP, between the treatment and control groups (108819).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related testosterone deficiency. It is unclear if oral D-chiro-inositol is beneficial in patients with age-related testosterone deficiency. Details: A very small clinical study in males aged 65-75 years with low-normal morning testosterone levels and signs and symptoms of androgen deficiency shows that taking D-chiro-inositol 600 mg twice daily for 30 days improves sexual function and physical strength when compared with baseline (108821). The validity of these findings is limited by the lack of a comparator group.
• Bipolar disorder. It is unclear if oral inositol is beneficial in patients with bipolar disorder. Details: Evidence is conflicting on whether inositol helps treat bipolar disorder in children. One very small preliminary study in children aged 5-12 years with bipolar disorder not on concomitant mood-stabilizing medications shows that taking inositol 80 mg/kg (maximum 2 grams) daily for 12 weeks reduces manic symptoms when compared to baseline. Additionally, taking a combination of inositol 80 mg/kg and high eicosapentaenoic acid omega-3 fatty acid capsules (EPA; Nordic Naturals) 1650-3000 mg daily for 12 weeks reduces manic and depressive symptoms when compared to baseline (95092). However, another more recent study with the same intervention and protocol shows that the combination of inositol and high eicosapentaenoic acid omega-3 fatty acid reduces symptoms of depression, but does not improve manic symptoms, when compared with either ingredient taken alone (111676).
• Chemotherapy-induced leukopenia. Oral inositol has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults undergoing breast cancer surgery and adjuvant chemotherapy shows that taking inositol orally 390 mg twice daily and applying IP-6 gel 4% twice daily to the surgical site, starting 2 weeks before adjuvant chemotherapy and stopping 2 weeks after the last cycle, attenuates reductions in white and red blood cell counts when compared with no intervention. Using inositol and IP-6 also improves breast and arm symptom scores and some quality of life scores; however, these improvements were not consistent over time.
• Diabetes. It is unclear if oral inositol is beneficial for the treatment of type 1 diabetes or the prevention of gestational diabetes. Details: Preliminary clinical research in patients with type 1 diabetes and a body mass index of at least 25 kg/m2 shows that taking a specific combination product containing D-chiro-inositol and folic acid (Chirofol 500, LJ Pharma) daily for 6 months, along with insulin therapy, decreases glycated hemoglobin (HbA1c) by approximately 0.5% when compared to taking folic acid alone with insulin therapy. However, there was no difference between groups with respect to insulin resistance or body mass index (95088). Most research shows that taking inositol during pregnancy prevents gestational diabetes. However, most studies conducted to date are of low quality and it is unclear if the results are generalizable. Meta-analyses of 4-7 clinical studies in pregnant adults, some with overweight and obesity, shows that taking myo-inositol 200-4000 mg daily may reduce the risk of gestational diabetes and gestational hypertension, improve 1- and 2-hour glucose tolerance test results, and reduce insulin requirements. Inositol may also be associated with improved infant outcomes such as increased gestational age at birth and reduced preterm delivery but does not seem to influence birth weight, NICU admission rate, neonatal hypoglycemia, the incidence of shoulder dystocia, macrosomia or cesarian delivery when compared with control (111664,111667,111671,111677,114560). The validity of these effects is limited by significant heterogeneity within the included studies, concerns about blinding, and overall low-quality evidence. Most clinical research shows that taking myo-inositol 2 grams plus folic acid 200 mcg twice daily (usually as Inofolic, Lo.Li. Pharma International), beginning during the first trimester and continuing throughout pregnancy, decreases the incidence of gestational diabetes by 57% to 92% when compared with folic acid alone in patients at risk for gestational diabetes. Myo-inositol seems to be more effective than D-chiro-inositol (91545,91548,95083,95084,100706,103750,104688). Subgroup analysis suggests that supplementation with lower doses of inositol, mimicking natural inositol occurring in the body, may not be effective at preventing gestational diabetes (114560). However, this analysis may have been inadequately powered to detect a difference between groups, and it is further limited by heterogenous methods between trials, including duration, population, and product. Other evidence is conflicting about whether inositol prevents gestational diabetes. One clinical study shows that taking a combination of myo-inositol 1.1 grams, D-chiro-inositol 27.6 mg, and folic acid 400 mcg (Inofolic Combi, Lo.Li. Pharma International) daily during pregnancy does not decrease the incidence of gestational diabetes when compared with folic acid alone in patients with a family history of diabetes (95082,103750). In patients eventually diagnosed with gestational diabetes, one small clinical study shows that taking myo-inositol 2 grams reduces the number of patients requiring insulin by at least 50% (104688), although another small clinical study shows that adding D-chiro-inositol, myo-inositol, or both to folic acid does not affect insulin resistance when compared with placebo (98945).
• Dyslipidemia. Although there has been interest in using oral inositol for hypercholesterolemia and hypertriglyceridemia, there is insufficient reliable information about the clinical effects of inositol for these conditions.
• Erectile dysfunction (ED). Oral inositol has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Another very small study in males with overweight or obesity, mild ED, and normal to low androgen levels shows that taking a combination product containing myo-inositol 4000 mg, alpha-lipoic acid, folic acid, and apple (Sinopol Forte) improves measures of erectile dysfunction when compared with baseline (111674). The validity of these effects is limited by the small sample size and the lack of a comparator group, and it is unclear if these effects are due to inositol, other ingredients, or the combination.
• Hypertension. Although there has been interest in using oral inositol for hypertension, there is insufficient reliable information about the clinical effects of inositol for this condition.
• Hypothyroidism. Inositol has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A meta-analysis of clinical and observational research in adults with hypothyroidism, subclinical hypothyroidism, and other thyroid disorders shows that taking a combination of inositol 600-1200 mg and selenium 83-166 mg orally daily for 6-12 months modestly improves thyroid stimulating hormone (TSH) levels and thyroxine levels when compared with control (114562). Clinical research in females aged 18 to 50 years with or at risk for subclinical hypothyroidism in Slovakia shows that taking myo-inositol 600 mg and selenium 83 mcg daily for 6 months reduces patient-reported hypothyroid symptoms including fatigue, menstrual cycle irregularity, and intolerance to heat or cold (110591). The interpretation of this result is limited by the lack of a control group. In addition, it is unclear if the effects in these studies are due to myo-inositol, selenium, or the combination.
• Infertility. It is unclear if oral inositol is beneficial in patients undergoing intracytoplasmic sperm injection (ICSI) or in vitro fertilization (IVF). Details: Several small studies in patients undergoing ICSI show that taking a specific combination product containing myo-inositol 4 grams and folic acid 400 mcg (Inofolic, Lo.Li. Pharma International S.r.l) daily, starting 1-3 months before ICSI and continuing until ovulation, improves fertilization rate, but does not improve implantation or pregnancy rates, when compared with taking folic acid alone (103752,108825). However, another moderate-sized clinical study in adults with infertility undergoing ICSI and IVF shows that taking the same combination of myo-inositol 4000 mg and folic acid 400 mcg daily for 2 months starting on the third day of the cycle improves mean number of oocytes, meiosis II oocytes, 2 pronuclear embryos, and clinical pregnancy and live birth rates when compared with taking folic acid alone (111672). The effects of inositol on fertility have been studied in patients with specific comorbidities. A case-control study in long-term survivors of lymphoma suggests that taking myo-inositol 400 mg and D-chiro-inositol 45 mg (Ovofert Fast, CRL Pharma) three times daily for 12 months is associated with reductions in follicle stimulating hormone (FSH), luteinizing hormone (LH), dyspareunia, and dysmenorrhea and a modest increase in antral follicle count of the right ovary when compared with control (111673). The validity of these effects is limited by a lack of blinding. Inositol has also been evaluated in females with polycystic ovary syndrome (PCOS). A meta-analysis of clinical studies in adults with PCOS undergoing IVF or ICSI shows that inositol does not improve pregnancy rates when compared to no treatment. However, inositol may increase clinical pregnancy rates when compared with metformin (111675). Inositol has also been evaluated in combination with other ingredients. A large clinical study in females planning to conceive shows that taking a combination product containing myo-inositol 4 grams, vitamin D, riboflavin, vitamin B6, vitamin B12, zinc, and probiotics does not improve time-to-conception, clinical pregnancy rates, or live birth rates when compared with a standard micronutrient supplement. However, the supplement shortens time-to-conception in adults with overweight to durations equivalent to patients who are not overweight, but lengthens time to conception in adults with obesity when compared with placebo (111665). It is unclear whether these effects are due to inositol, other ingredients, or the combination.
• Insomnia. It is unclear if oral inositol is beneficial for improving sleep during pregnancy. Details: Clinical research shows that taking myo-inositol 2 grams plus folic acid 200 mcg (Inofolic, Lo.Li. Pharma International) before bed for 10 weeks, starting at 14 weeks gestation, improves overall measures of sleep quality by a small amount when compared with folic acid alone. However, this improvement was not maintained until 37-38 weeks' gestation. Also, the study was not limited to patients with poor sleep quality during pregnancy, but to any healthy pregnant individual (104687).
• Lithium-induced side effects. It is unclear if oral inositol is beneficial for reducing lithium-induced side effects. Details: A small clinical study suggests that taking inositol 6 grams daily for 10 weeks may improve psoriasis associated with lithium therapy when compared with baseline (11972). However, taking inositol orally does not seem to improve other lithium-induced adverse effects, such as tremor, thirst, and changes in thyroid and adrenal function (2027).
• Lung cancer. It is unclear if oral inositol is beneficial for slowing the rate of bronchial dysplasia. Details: Preliminary clinical research in smokers with bronchial dysplasia considered at high risk for lung cancer shows that taking myo-inositol (Tsuno Food Industries Co., Ltd.) 9 grams orally once daily for 2 weeks then twice daily for 6 months, does not increase the rate of complete or partial response when compared with placebo (95090).
• Metabolic syndrome. Oral inositol has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adults with metabolic syndrome shows that taking a specific combination product containing D-chiro-inositol 40 mg, Ceylon cinnamon 250 mg, glucomannan 1000 mg, and inulin 200 mg orally daily for 4 months modestly improves total cholesterol levels and body weight, but not serum glycated hemoglobin, low-density lipoprotein levels, high-density lipoprotein levels, or triglyceride levels when compared with no intervention (114552). It is unclear if this effect is due to D-chiro-inositol, other ingredients, or the combination.
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral inositol is beneficial for NAFLD. Details: A small clinical study in adults with NAFLD and obesity shows that taking myo-inositol powder 4 grams daily for 8 weeks does not improve liver health markers, such as liver function test levels or liver steatosis, but does improve some components of lipid profiles, glycemic indices, and anthropometric measures when compared to baseline (111304) However, this study may have been inadequately powered to detect differences in some of the outcomes.
• Obesity. It is unclear if oral inositol is beneficial in patients with overweight or obesity. Details: A meta-analysis of 15 clinical studies in adults shows that taking inositol 600-4450 mg daily for 6-48 weeks decreases body mass index (BMI) by about 0.4 kg/m2. Subgroup analysis suggests that myo-inositol may be beneficial at a dosage less than 1000 mg for less than 12 weeks, especially in patients with polycystic ovary syndrome (PCOS) and overweight or obesity, with higher baseline BMI, and above 40 years of age (111666). However, the validity of this finding is limited by significant heterogeneity in the included studies.
• Obsessive-compulsive disorder (OCD). It is unclear if oral inositol is beneficial in patients with OCD. Details: One preliminary clinical study in adults with OCD shows that taking inositol 18 grams daily for 6 weeks improves Yale-Brown Obsessive Compulsive Scale scores when compared with placebo (2186). However, taking inositol does not seem to improve the severity or type of OCD symptoms in patients already taking a selective serotonin reuptake inhibitor (91556). Both of these studies were small, and treatment was administered for only 6 weeks.
• Panic disorder. Oral inositol seems to improve symptoms of panic disorder. Details: A very small clinical study shows that taking inositol 12 grams daily reduces the severity and rate of panic attacks and the severity of agoraphobia over 4 weeks of treatment when compared with placebo (2184). Another very small clinical study shows that taking inositol 18 grams daily for one month may be as effective as fluvoxamine 150 mg daily for treatment of panic disorder (10387). However, the one-month duration may not have provided adequate time to see the full effects of fluvoxamine.
• Post-traumatic stress disorder (PTSD). It is unclear if oral inositol is beneficial in patients with PTSD. Details: Preliminary clinical research shows that taking inositol 12 grams daily for 4 weeks does not improve distress when compared with placebo in patients with PTSD (91557).
• Pregnancy-induced hypertension. It is unclear if oral inositol is beneficial for preventing hypertension during pregnancy. Details: In patients with a body mass index (BMI) between 25-29.9 kg/m2, preliminary clinical research shows that taking myo-inositol 2 grams plus folic acid 200 mcg (Inofolic, Lo.Li. Pharma International) twice daily, beginning during the first trimester and continuing throughout pregnancy, decreases the incidence of pregnancy-induced hypertension by 66% when compared with folic acid alone (104688).
• Psoriasis. It is unclear if oral or topical inositol is beneficial for improving symptoms of psoriasis. Details: One small clinical study shows that taking inositol 6 grams daily for 10 weeks does not improve symptoms of psoriasis in a small group of patients when compared to baseline. However, taking this dose of inositol has a moderate effect on overall symptoms in patients with psoriasis related to lithium use (11972). Preliminary clinical research also shows that topical use of D-chiro-inositol is unlikely to be beneficial for reducing overall symptoms of psoriasis. Topical application of inositol 0.25% or 1% for 6 weeks improves overall symptoms when compared with baseline. However, the inositol-containing creams were no more effective than the control cream (104686). Inositol has also been evaluated in combination with other ingredients. A small prospective observational study in adults with mild plaque psoriasis suggests that applying amino-inositol and urea 40% cream (Inosit U40, Biogena) 1-2 times daily for 4 weeks is associated with reductions in the severity and extent of psoriasis symptoms and improvements in quality of life measures when compared to baseline (111668). The validity of these effects is limited by a small sample size, a lack of a comparator group, insufficient blinding, and the observational study design.
• Trichotillomania. It is unclear if oral inositol is beneficial for reducing hair pulling. Details: Preliminary clinical research shows that taking inositol in doses ranging from 6-18 grams daily over a period of 10 weeks is no more effective than placebo in reducing subjective or clinician-documented symptoms of hair pulling in patients with trichotillomania (95089). More evidence is needed to rate inositol for these uses.

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LIKELY EFFECTIVE

• Delayed sleep phase syndrome (DSPS). Oral melatonin shortens the time needed to fall asleep in children and adults with DSPS. Details: Most clinical research shows that taking melatonin orally reduces the length of time needed to fall asleep and advances sleep onset time in young adults and children with DSPS (8244,12226,15005,62714,62792,63055,88288,88290,89509). In adults, 0.3-5 mg daily for up to 9 months has been used (8244,62714,62792,63055,88290,89509). In children, 1-6 mg before bedtime for up to one month has been used (62714,62792,89509). In addition to improving sleep, melatonin also improves measures of quality of life such as mental health, vitality, and bodily pain in young adults with DSPS (8244,12226,15005). However, relapse to pre-treatment sleeping patterns seems to occur within one year after stopping supplementation (63048).
• Non-24-hour sleep wake disorder. Oral melatonin improves non-24-hour sleep wake disorder in blind children and adults. Details: Taking oral melatonin 0.5-4 mg daily in children and 0.5-10 mg daily in adults for up to 6 years helps improve circadian rhythm sleep disorders in blind children and adults (1082,1744,1749,6585,62346,62350).

POSSIBLY EFFECTIVE

• Beta blocker-induced insomnia. Oral melatonin seems to improve sleep in patients with insomnia related to the use of beta-blockers. Details: Beta-blockers such as atenolol and propranolol seem to decrease endogenous melatonin levels (1780). This might result in insomnia as a side effect. Clinical and preclinical research shows that taking a melatonin supplement might decrease the insomnia caused by beta-blockers (1062,89502). Taking melatonin 5 mg at night after taking atenolol 100 mg appears to attenuate the changes in sleep onset latency, total wake time, and wakefulness after sleep onset when compared with taking atenolol 100 mg alone (1062). Also, in patients taking atenolol or metoprolol, taking melatonin 2.5 mg one hour before bedtime for 20-28 days increases total sleep time by 13-37 minutes and decreases sleep latency by 8-14 minutes when compared with placebo (89502).
• Cancer. In patients with various types of cancer, most research shows that oral or combined intramuscular/oral melatonin in combination with chemotherapy or other treatments seems to improve tumor regression and survival rates. Details: There is some evidence that taking combined high-dose melatonin with conventional chemotherapy or with interleukin-2 (IL-2) might improve tumor regression rate in patients with breast, lung, kidney, liver, pancreatic, stomach, or colon cancer (1692,5854,5855,5857,7040,7043,8268,62407,62844). Melatonin plus chemotherapy in patients with metastatic solid tumors seems to increase the regression rate and one-year survival rate by about 40% to 50% when compared with chemotherapy alone (7040,62407,62844,89504). The addition of melatonin also seems to help reduce chemotherapy toxicities, including hematologic complications, cachexia, asthenia, and neuropathy (8268,62844,89504). There is also some preliminary evidence that melatonin alone, orally or intramuscularly, might improve stabilization rate and possibly one-year survival rate in patients with resistant or untreatable neoplasms of the lung, liver, pancreas, colon, breast, or brain (1080,1688,1693,2566). Also, when used in combination with radiotherapy, high-dose melatonin seems to increase the survival time and percent survival in patients with brain glioblastomas when compared with radiotherapy alone (62991). However, high-dose melatonin treatment does not seem to improve the survival of patients with brain metastases who receive radiation therapy (62455). Melatonin 10-40 mg daily has been used in most clinical trials (1080,1692,1693,2566,5854,5855,5857,7040,7043,8268)(62455,62844,62991,89504). In one study, melatonin 20 mg intramuscularly daily for 2 months, followed by oral melatonin 10 mg daily as maintenance, was used (1688). The effect of melatonin on quality of life and sleep quality in patients with cancer has also been investigated. A meta-analysis of six clinical trials shows that taking melatonin 20 mg daily does not improve sleep quality or quality of life when compared with a control, usually placebo. The duration of studies varied widely; from a period of 7 days or until death. However, there was a modest effect of melatonin on symptoms of depression in patients taking it for at least 14 days or those who underwent surgery (109697).
• Emergence delirium. Oral melatonin seems to be beneficial for reducing sevoflurane-induced agitation in children. It is unclear if oral melatonin is beneficial for adults undergoing surgery. Details: A meta-analysis of clinical research in perioperative adults shows that taking melatonin 3-5 mg or ramelteon 8 mg orally daily for 1-7 days reduces the risk of emergence delirium by 59% when compared with placebo or no treatment. However, the validity of these results is limited by high heterogeneity (112053). In children, clinical research shows that taking melatonin reduces the incidence of sevoflurane-associated emergence delirium (97440,106292,113216). Meta-analyses of 3-4 small clinical studies in children aged 2-9 years show that taking melatonin 0.05-0.5 mg/kg 40-45 minutes prior to sevoflurane reduces the incidence of agitation by 60% when compared with placebo (97440,113216). The most recent analysis also shows that taking melatonin reduces the incidence of agitation by 52% when compared with midazolam (113216). Most research shows that doses of melatonin 0.2 mg/kg or greater may be most effective (97440,106292). However, clinical research shows that taking melatonin is less effective than dexmedetomidine (109701,113216). One study shows that taking melatonin 0.5 mg/kg before surgery is 55% less effective than intranasal dexmedetomidine 2 mg/kg for reducing the incidence of sevoflurane-associated emergence delirium (109701).
• Hypertension. Oral controlled-release melatonin seems to reduce blood pressure by a small amount in patients with hypertension. Immediate-release melatonin may not have the same effect. Details: Controlled-release melatonin 2-24 mg, taken before bedtime for up to 4 weeks, seems to lower systolic blood pressure (SBP) by 4-6 mmHg and diastolic blood pressure (DBP) by about 4 mmHg in individuals with essential hypertension or high blood pressure at nighttime (62359,62416,62441,62826,108947). Some evidence shows that immediate-release melatonin does not have this effect (62826). Some evidence also suggests that melatonin seems to slightly reduce blood pressure in patients without hypertension, but to a lesser degree (103689). However, a very small clinical study in healthy young adults consuming a high sodium diet (6900 mg daily) shows that taking melatonin 10 mg before bedtime for 10 days decreases nighttime SBP but does not improve nighttime DBP, daytime SBP or DBP, 24-hour SBP or DBP, or nocturnal dipping of SBP or DBP when compared with placebo (112442).
• Insomnia. In patents with insomnia, oral melatonin seems to shorten the time it takes to fall asleep by about 7-12 minutes, although the effect on the amount of time asleep is inconclusive. Melatonin is more likely to be beneficial in older adults or people with certain comorbidities. Details: Short-term melatonin treatment appears to modestly reduce the time it takes to fall asleep (sleep latency) in otherwise healthy adults with insomnia. This reduction in sleep latency appears to amount to only about 7-12 minutes and might not be considered clinically relevant. Melatonin does not appear to improve sleep efficiency and may only increase total sleep time by about 8 minutes (15005,88290). Despite lack of substantial improvements in objective measures, some patients report minor improvement in subjective feelings of sleep quality (1070,1083,12226,88290). In children aged 6-12 years with insomnia due to delayed onset of sleep, melatonin 5 mg or 0.05-0.15 mg/kg at bedtime for up to 4 weeks seems to shorten the time that it takes to fall asleep and increases the duration of sleep (9708,62345,62770). More evidence is needed on the long-term effects of melatonin for insomnia. Some evidence shows that taking oral melatonin might be most beneficial for insomnia in elderly patients who could be melatonin deficient (1072,1729,1738,1754,7081,15005,62357,62465,62472,62613)(62776,62789). Taking sustained-release melatonin preparations 2 mg daily seems to improve sleep maintenance and sleep quality in elderly individuals (1738,1754,62465,62472,62613,62776), while immediate-release preparations seem to decrease sleep latency (1738,63041). In these clinical trials, controlled-release, fast-release, or slow-release melatonin 2-3 mg before bedtime for up to 29 weeks has been used (1072,1738,1754,7081,62357,62465,62472,62613,62776,62789). However, using a melatonin patch placed on the gums does not improve sleep parameters in elderly patients with insomnia (63062). Some research shows that taking melatonin when taken either alone or in combination with other sleep aids such as bright-light treatment seems to be beneficial for insomnia in patients with certain comorbid conditions. Taking melatonin 2-12 mg for up to 4 weeks has been used to improve insomnia in patients with depression (1053,1729), schizophrenia (8245,62452), bipolar disorder (62140), asthma (62375), cystic fibrosis (62708), hospitalization (9709,106295), and insomnia termed "ICU syndrome", which refers to sleep disturbances while in the intensive care unit (8240). Insomnia is also improved in children with epilepsy aged 3-12 years taking 6-9 mg of melatonin before bedtime for 4 weeks and children aged 3 months to 2 years taking 3 mg of melatonin before bedtime for 2 weeks (62394,99342,113223), and quality of sleep is modestly improved in adults with epilepsy taking 3 mg before bedtime for 8 weeks (110299). There is also evidence that melatonin can improve total sleep time and sleep-onset latency in children with tuberous sclerosis (1747), autism spectrum disorders (1056,62811,88286,96318,106293,110290), developmental disabilities (9707), and neurodevelopmental disorders (21819,62143,88283). It also appears to decrease sleep latency and increase sleep time in adults and children with intellectual disabilities, with or without epilepsy (62373,62561). While some evidence shows that fast-release melatonin is more effective for improving the time to fall asleep in children with sleep-wake cycle disturbances and neurodevelopmental disabilities, it is unclear if controlled-release melatonin provides any additional benefits in this population (62143,95746). However, there is conflicting evidence regarding the effects of melatonin in patients with insomnia and comorbid conditions such as Alzheimer disease or dementia. Some clinical research shows that taking melatonin 3-5 mg before bedtime for up to 10 weeks, either alone or in combination with bright-light treatment, improves impaired sleep related to Alzheimer disease or dementia (1729,62474,63059). But not all research agrees. Meta-analyses of several clinical studies show that taking melatonin 3-10 mg daily improves subjective sleep quality, but not objective outcomes such as number of awakenings at night and sleep efficiency in these patients. Also, immediate-release melatonin 2.5-10 mg or prolonged-release melatonin 1.5-2.5 mg for 10 days to 24 weeks shows inconsistent effects on total sleep time at night in patients with Alzheimer disease (96319,96320). There is also mixed evidence regarding the effects of melatonin in patients with Parkinson disease. Some subjective outcomes such as sleep quality seem to improve. However, the improvement might not be clinically significant, and objective outcomes such as sleep efficiency and total sleep time at night do not seem to improve (62403,62454,62829,96320). Melatonin has also been evaluated in postoperative patients and patients with traumatic brain injury (TBI). Taking melatonin before bed does not improve sleep quality soon after tracheostomy, laparoscopic cholecystectomy, or total knee arthroplasty (62439,62552,99343,100255) or 2-6 weeks after total joint arthroplasty (106305). In adults with TBI, one clinical study shows that taking prolonged-release melatonin (Circadin, Sigma Pharmaceuticals) 2 mg two hours prior to bedtime for 4 weeks improves sleep quality, efficiency, and fatigue when compared with placebo. However, melatonin did not improve sleep onset latency or daytime sleepiness. There appears to be no association between TBI severity and the effect of treatment (96317). There is mixed evidence regarding the effect of melatonin in patients undergoing hemodialysis. Some evidence shows that taking melatonin (Pharma Nord) 3 mg before bed for 6 weeks reduces time needed to fall asleep, improves sleep efficiency, and increases actual sleep time when compared with placebo (62521). Other clinical research in patients undergoing hemodialysis shows that taking immediate-release melatonin 3 mg (Puritans Pride, USA) for 3 months modestly improves various sleep measures when compared with placebo. After treatment, 63.0% of those taking melatonin had no insomnia compared with 7.7% of those taking placebo (110291). However, other evidence shows that taking immediate-release melatonin (Pharma Nord) 3 mg nightly for 12 months does not improve quality of life or sleep efficiency in these patients, indicating that melatonin may not improve sleep long-term (89501). Finally, limited evidence shows that melatonin does not improve insomnia in patients with substance use disorders (97441).
• Jet lag. Taking oral melatonin 2-3 mg daily while travelling seems to improve alertness and reduce daytime sleepiness in people with jet lag. It is unclear if it improves sleep efficiency in this population. Higher doses might have a hypnotic effect. Details: Most research shows that melatonin can modestly improve certain symptoms of jet lag such as alertness and psychomotor performance. Melatonin also seems to improve, to a lesser extent, other jet lag symptoms such as daytime sleepiness and fatigue (12226). Melatonin might not be effective for decreasing the time to fall asleep (sleep latency) or sleep efficiency in patients with jet lag (6496,14283), although some research shows a beneficial effect of melatonin on these outcomes (62364). Doses between 0.5-5 mg appear to be equally effective. Although doses of up to 8 mg have been used, doses greater than 5 mg do not seem to be more effective and seem to produce a greater hypnotic effect. Travelers traveling eastward through five or more time zones may find 2-3 mg of melatonin, either slow-release or fast-release, to be useful when taken at local bedtime on the day of arrival and for 2-5 nights thereafter. Taking melatonin in advance of travel does not help prevent jet lag. The usefulness of melatonin for westward travel or over fewer time zones is less clear, although some evidence suggests that slow-release formulations are less effective than fast-release preparations (1049,1077,1079,1085,1722,8273,9181,9750,62706).
• Migraine headache. Oral melatonin 3-4 mg seems to prevent migraines when used prophylactically. It is unclear if oral melatonin is beneficial for treating migraine. Details: Melatonin production might be altered in people with migraine headache (6712,96316). Meta-analyses and individual clinical studies in adults have shown that taking melatonin modestly reduces migraine severity, duration, and frequency, and increases the likelihood of a 50% reduction in the baseline frequency of migraine, when compared with placebo or baseline. Immediate- or prolonged-release melatonin (occasionally as Circadin, Sigma Pharmaceuticals) in doses of 3-4 mg each evening for up to 6 months have been used in these studies (12149,96316,97438,103486,110286). Meta-analyses have included two or three individual clinical trials (103486,110286). One meta-analysis shows that taking melatonin reduces the frequency of migraine days by about 1.7 (103486). An additional meta-analysis in adults with migraines shows that taking melatonin modestly reduces the use of analgesic medications from baseline, when compared with placebo (110286). In contrast, other clinical research shows that taking extended-release melatonin (Circadin, Neurim Pharmaceuticals Ltd.) 2 mg nightly for 8 weeks does not reduce migraine attack frequency when compared with placebo (62784). Some clinical research also shows that melatonin is as effective as standard treatment for migraine prevention. Some research shows that taking melatonin 3 mg daily for 12 weeks is as effective as amitriptyline 25 mg in reducing migraine frequency, intensity, and duration, as well as reducing analgesic use (96316). A meta-analysis of two clinical trials shows that taking melatonin 3 mg each evening for 8-12 weeks is as effective as standard treatment; however, only one study each compared melatonin with amitriptyline (96316) and valproate (110286). More research comparing melatonin with standard treatments is needed. Melatonin has also been investigated in children. Preliminary clinical research in children 5-15 years of age with migraine headache shows that taking melatonin 0.3 mg/kg daily for 90 days reduces migraine frequency, severity, and duration, and decreases analgesic use when compared to baseline (97446). Some research also suggests that melatonin might help to TREAT migraine headache in children and adolescents aged 9-17 years. Preliminary clinical research shows that taking melatonin 1-8 mg reduces pain by a small amount 2-4 hours later. The higher doses of 2 mg for children weighing less than 40 kg and 8 mg for children weighing at least 40 kg seemed to have the greatest benefit (103487). This study is limited by the lack of a comparator group and a very high drop-out rate.
• Pre-procedural anxiety. Most research shows that oral or sublingual melatonin reduces preoperative anxiety in adults. The benefit in children is unclear. Details: A meta-analysis of 18 clinical studies in adults shows that taking oral or sublingual melatonin 3-10 mg or 0.05-0.4 mg/kg 20-120 minutes prior to surgery reduces preoperative anxiety by an average of 12 points on a 100-point visual analogue scale when compared with placebo. It also reduces postoperative anxiety by about 5 points when compared with placebo. Furthermore, a meta-analysis of 7 small clinical trials suggests that melatonin is comparable to benzodiazepines such as midazolam, oxazepam, or alprazolam for reducing preoperative anxiety (105005). In some cases, melatonin might also be preferable to benzodiazepines because it does not cause anterograde amnesia, respiratory depression, or impairment of cognitive and psychomotor skills (88299,99337). However, research in children is conflicting. Two small clinical studies in children aged 2-10 years preparing to undergo outpatient elective surgery show that taking melatonin 0.05-0.5 mg/kg 30-45 minutes before anesthesia is less effective than midazolam 0.5 mg/kg for reducing preoperative anxiety, including during separation from parents and when putting on the anesthesia mask (62601). In contrast, another small clinical study in children aged 2-5 years undergoing minor elective surgery shows that taking oral melatonin 0.25-0.5 mg/kg 1 hour before anesthesia is similar to midazolam 0.25-0.5 mg/kg for reducing anxiety when separating from parents and when putting on the anesthesia mask (62399). A third study in children aged 3-8 years found no differences between melatonin 0.3 mg/kg, midazolam 0.3 mg/kg, and placebo for reducing preoperative anxiety (106292).
• Pre-procedural sedation. Oral melatonin might reduce the sedative dose required to achieve adequate sedation in children. It is unclear if oral melatonin is beneficial for this purpose in adults. Details: A clinical study in children aged 5-14 years undergoing surgery shows that oral melatonin 0.5 mg/kg reduces the propofol dose required for adequate sedation by 0.77 mg/kg when compared with midazolam 0.5 mg/kg (97444). However, taking melatonin 0.5 mg/kg 45 minutes before surgery is less effective than intranasal dexmedetomidine 2 mg/kg for successful mask acceptance and parental separation (109701). A meta-analysis of clinical and observational studies in children undergoing non-operative procedures, such as electroencephalogram (EEG) and magnetic resonance imaging (MRI), suggests that enteral or parenteral melatonin is no better for adequate sedation than sleep deprivation or chloral hydrate (105884). This finding is limited by imprecision, inconsistency, and a high risk of bias. A small clinical study in adults undergoing total abdominal hysterectomy shows that taking extended-release melatonin 5 mg, 90 minutes before surgery, decreases the use of midazolam for sedation during surgery when compared with placebo (108945). However, the validity of this finding is unclear, as 0% of patients in the melatonin group required midazolam, compared with 100% of patients in the placebo group. In adults undergoing lower extremity orthopedic surgery with spinal anesthesia, a small study shows that giving melatonin 10 mg orally the night before surgery, followed by 10 mg 2 hours prior to surgery, increases the sedation score when compared with placebo (108951).
• Sunburn. Most research shows that topical melatonin seems to protect against erythema from ultraviolet (UV) light exposure. Details: When applied prior to UV light exposure, a gel containing melatonin 0.05% to 2.5% seems to significantly decrease erythema (1066,1768,1769). In one study, topically applied melatonin in combination with vitamin E 2% and/or vitamin C 5%, was modestly photoprotective when used prior to UV exposure, but had no effect when used during or after UV exposure (4713,4714). Other preliminary clinical research shows that applying a cream containing melatonin 12.5% prior to sun exposure reduces erythema in adults with high sun reactivity, but not in those with mild to moderate sun reactivity. Creams containing melatonin 0.5% or 2.5% did not reduce erythema in any skin types when compared with placebo (97443). The differences in these findings may be related to the different topical formulations used.
• Temporomandibular disorders (TMD). Oral melatonin seems to moderately reduce pain in females with TMD. Details: Clinical research shows that taking melatonin 5 mg at bedtime for 4 weeks reduces pain by 44% and increases the ability to withstand pain by 39% when compared with placebo in females with TMD. This results in reduced analgesic use and improved sleep quality (89508).
• Thrombocytopenia. Oral melatonin seems to improve and prevent thrombocytopenia associated with cancer, cancer treatment, and other disorders. Details: Clinical research shows that taking melatonin can improve thrombocytopenia associated with cancer, cancer treatment, and other disorders. Melatonin 20-40 mg daily beginning up to 7 days before chemotherapy and continuing for up to four chemotherapy cycles or until disease progression has been used (1694,1695,1696,1697,2564,8268).

POSSIBLY INEFFECTIVE

• Athletic performance. Most research suggests that oral melatonin does not improve athletic performance or physical strength. Details: Taking melatonin 6 mg one hour prior to heavy resistance exercise does not seem to improve maximal strength or maximal jumping ability (62424). Also, taking melatonin 5 mg at night does not appear to improve exercise performance the following morning in healthy athletes (62179). Furthermore, taking melatonin 5 mg 15 minutes prior to exercise does not appear to impact endurance during a cycling trial when compared with placebo (99338). However, some research disagrees. One small clinical trial in professional soccer players shows that taking melatonin 5 mg daily during a six-day training schedule modestly attenuates deterioration in physical performance, such as jumping, agility, and sprints, when compared with placebo (109700).
• Cachexia. Oral melatonin does not seem to improve appetite or body composition in patients with cachexia and cancer. Details: Clinical research in cachectic patients with advanced lung or gastrointestinal cancers shows that taking melatonin 20 mg each evening for 28 days does not improve appetite, body weight, or body composition when compared with placebo (88287).
• Cancer-related fatigue. Oral melatonin does not seem to improve fatigue in patients with cancer. Details: A meta-analysis of five clinical trials shows that taking melatonin does not reduce fatigue in patients with cancer (109697). Most studies used melatonin 20 mg daily, with a duration of 7 days to one year (99344,109697). Although most studies included in the analysis were small, one contained over 700 patients and lasted one year. However, some research disagrees. Preliminary clinical research in adults with breast cancer shows that taking melatonin 18 mg orally daily for 2 years moderately improves fatigue scores when compared with placebo (112054).
• Cancer-related pain. Oral melatonin does not seem to improve pain in patients with cancer. Details: A meta-analysis of five clinical trials shows that taking melatonin does not reduce pain in patients with cancer (109697). Most studies used melatonin 20 mg daily, with a duration of 10 days to one year (109697). Although most studies included in the analysis were small, one contained over 700 patients and lasted one year.
• Critical illness (trauma). Oral melatonin does not seem to be beneficial for reducing hospital stay in critically ill patients. Details: A meta-analysis of clinical research in critically ill patients shows that taking melatonin does not reduce the length of stay in the ICU or the hospital, or affect mortality or sleep quality, when compared with placebo (109696). One additional small clinical study shows that receiving melatonin 3 mg through a nasogastric tube once at 9 pm, followed by a 0.5 mg hourly maintenance dose for 6 hours during the overnight period, does not improve sleep when compared with placebo in patients in the ICU that are being weaned off sedatives and mechanical ventilation (104997).
• Dementia. Oral melatonin does not seem to improve behavior or cognition in patients with dementia. However, it might reduce evening confusion (sundowning). Details: Most clinical research shows that taking melatonin does not improve cognition or behavioral or affective symptoms in patients with probable Alzheimer disease or other forms of dementia (62421,62530,96319). However, some research shows that taking melatonin 2.5-3 mg before bedtime for up to 10 weeks reduces sundowning, which is the confusion and restlessness experienced by some dementia patients in the evening (62788).
• Infertility. Oral melatonin does not seem to increase fertility in females undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Details: Some clinical research shows that taking melatonin does not improve fertility rate or clinical pregnancy rate in adults undergoing IVF, although oocyte and embryo quality might be improved (62775,62818,62819,88297,89512). Also, results from meta-analyses of clinical research show that melatonin does not improve clinical pregnancy rate, total number of oocytes retrieved, or the rate of miscarriage, although it seems to increase the number of mature oocytes (89505,106304). Most studies have used single doses of 3 mg daily which may not be adequate (106304). Melatonin has also been evaluated in adults undergoing ICSI. Although one study shows that taking melatonin improves the fertilization rate, the clinical pregnancy rate was not evaluated (88297). Other research in females taking melatonin and undergoing ICSI does not show an increase in clinical pregnancy rate (97445).
• Shift work disorder. Oral melatonin does not seem to improve sleep in individuals doing shift work. Details: Taking melatonin orally doesn't seem to significantly improve the time it takes to fall asleep (sleep latency), sleep efficiency, or adjustment to rotating shift work. However, slight increases in total sleep time during the day or overall sleep quality may occur (1052,1054,1721,14283,62200,62401,62462,62942).

LIKELY INEFFECTIVE

• Benzodiazepine withdrawal. Oral melatonin does not facilitate benzodiazepine discontinuation in patients with insomnia. Details: Although some small studies show benefit (349,1751), results from larger clinical studies and a meta-analysis of clinical research show that taking melatonin 2-5 mg before bedtime for up to 6 weeks does not help facilitate benzodiazepine discontinuation in patients with insomnia (62464,62467,63075,88295,96321,96323).
• Depression. Most research shows that oral melatonin does not reduce symptoms of depression or prevent depression. In some patients, taking melatonin might make symptoms worse. Details: Most research shows that taking melatonin 5-10 mg daily before bedtime for 4-12 weeks, alone or with fluoxetine, does not improve depression symptoms in patients with rapid cycling bipolar disorder (1766) or major depressive disorder (MDD) (1053,62746,96326). However, some research shows that taking slow-release melatonin 3 mg in combination with immediate-release buspirone 15 mg daily for 6 weeks is more effective at improving depression severity and depression symptoms than placebo or buspirone alone in patients with MDD (88289). However, buspirone is not commonly used for the management of depression. Also, there is some concern that oral melatonin may worsen symptoms in some patients with unipolar or bipolar depression (1764). Evidence regarding the effects of melatonin for preventing depression is unclear. One clinical study shows that taking melatonin 6 mg daily for 12 weeks reduces the percentage of breast cancer patients who develop depression following a lumpectomy or mastectomy by about 75% when compared with placebo when an intention to treat analysis is used. However, when only patients who took all of the doses are considered, melatonin does not appear to have an effect (89511). Also, a meta-analysis of clinical research including two studies in patients with irritable bowel syndrome (IBS) who were at risk for depression shows that melatonin does not prevent depression when compared with placebo (96326).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Acute kidney injury (AKI). It is unclear if oral melatonin is beneficial for acute kidney injury. Details: A meta-analysis of randomized clinical trials in adults with drug-induced acute kidney injury shows that taking melatonin 3-30 mg daily for up to 6 days modestly improves glomerular filtration rate, but not serum creatinine or incidence of acute kidney injury, when compared with placebo (111463). Another meta-analysis of 5 clinical trials shows that taking melatonin inhibits the occurrence of acute kidney injury in at risk patients by 44% when compared with placebo. However, changes in serum creatinine and urea nitrogen were not statistically significant. Doses of melatonin varied from single doses of up to 5 mg and 6 mg to 30 mg daily for 5 to 14 days (113225).
• Age-related macular degeneration (AMD). It is unclear if oral melatonin prevents vision loss in patients with AMD. Details: Preliminary clinical research shows that taking melatonin 3 mg daily for 3-6 months may delay the loss of clear vision in individuals with AMD when compared with baseline (62419). The validity of this finding is limited by the lack of a comparator group.
• Atopic dermatitis (eczema). Oral melatonin might improve some symptoms of atopic dermatitis. However, it is unclear if it improves sleep in this population. Details: Preliminary clinical research in children ages 1-18 years with atopic dermatitis and sleep disturbance shows that taking melatonin 3 mg daily for 4 weeks modestly reduces the overall atopic dermatitis symptom score by 19% when compared with placebo (97439). In another clinical study in children with atopic dermatitis, taking melatonin 6 mg daily 1 hour before bedtime for 6 weeks seems to improve disease severity and sleep quality when compared with placebo (99347). It is unclear whether melatonin improves sleep latency in this population, as conflicting results exist (97439,99347).
• Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral melatonin is beneficial for ADHD. Details: Some small clinical studies in children with ADHD who are taking stimulants show that melatonin 3-5 mg daily for up to 3 months might reduce insomnia when compared with placebo (9980,15034). However, improved sleep related to melatonin treatment does not seem to result in fewer symptoms of ADHD (15034).
• Autism spectrum disorder. It is unclear if oral melatonin is beneficial for this condition. Details: One clinical trial in children aged 6-15 years with autism spectrum disorder shows that taking melatonin (Nobelpharma Co., Ltd) 1 mg or 4 mg before bedtime does not affect behavior when compared with placebo. However, this study was designed to evaluate sleep outcomes, not behavior, as a primary endpoint (106293). Also, a secondary analysis of results from a clinical trial in children with autism spectrum disorder shows that taking prolonged-release melatonin mini-tablets (PedPRM) 2-5 mg nightly for 13 weeks improves externalizing behavior in 26% more patients when compared with those taking placebo. There was no difference between groups in behaviors such as hyperactivity, inattention, emotional behavior, and relationships with peers (101256). The validity of these findings is limited by the secondary nature of the analysis, which was not designed to evaluate these outcomes.
• Benign prostatic hyperplasia (BPH). It is unclear if oral melatonin is beneficial for BPH. Details: One very small clinical study shows that taking controlled-release melatonin 2 mg nightly for 4 weeks reduces excessive urination at night in some men with BPH when compared with placebo. However, it is unclear if this improvement is clinically significant (62360).
• Bipolar disorder. It is unclear if oral melatonin is beneficial for this condition. Details: Preliminary clinical research shows that taking melatonin 3 mg at bedtime for 30 days increases sleep duration and reduces mania severity when compared to baseline in patients with bipolar disorder and treatment-resistant insomnia (62140). However, other research shows that melatonin is not beneficial in patients with bipolar disorder when compared with placebo. Taking melatonin 3-10 mg daily before bedtime for 3-12 weeks does not seem to improve mania or other symptoms when compared with placebo (1766,103694). Also, taking a specific brand of slow-release melatonin (Cronocaps, Productos Medix) 5 mg each evening for 8 weeks may attenuate the increase in blood pressure and fat mass that is associated with use of second-generation antipsychotics, but it does not appear to improve mania or depression in patients with bipolar disorder (88300). There is also some concern that oral melatonin may worsen symptoms in some patients with bipolar depression (1764).
• Bronchopulmonary dysplasia. It is unclear if oral melatonin reduces the risk of bronchopulmonary dysplasia (BPD) in premature infants. Details: A small clinical study in premature infants with respiratory distress syndrome who received surfactant shows that giving melatonin 3 mg daily for 7 days reduces the incidence of BPD to 45%, compared with 60% in those not receiving melatonin. Melatonin also reduced the duration of hospital stay, need for mechanical ventilation, and mortality (108948).
• Chronic fatigue syndrome (CFS). It is unclear if oral melatonin is beneficial for patients with CFS. Details: Many patients with CFS have circadian rhythm disturbances. Some very small clinical studies have evaluated the use of melatonin for addressing these disturbances. One study shows that taking melatonin 5 mg in the evening for 12 weeks might improve some measures of fatigue, concentration, motivation, and activity when compared with baseline (14437). However, other preliminary clinical research shows that taking the same dose of melatonin does not improve CFS symptoms when compared with placebo (9705). Melatonin has also been studied in combination with zinc. In patients with CFS, taking melatonin 1 mg plus zinc 10 mg before bedtime for 16 weeks modestly reduces self-reported levels of physical fatigue, but not self-reported cognitive or psychological symptoms, mood, sleep quality, or quality of life (QOL) measures, when compared with placebo. However, some measures of sleep quality and QOL worsened within 4 weeks of melatonin discontinuation, suggesting that there may have been a modest benefit (106241). It is unclear whether any benefit is related to melatonin, zinc, or the combination. Also, all patients in this study were White females, limiting the generalizability of the results.
• Chronic obstructive pulmonary disease (COPD). It is unclear if oral melatonin is beneficial for COPD. Details: Some clinical research shows that taking melatonin 3 mg daily for 3 months improves shortness of breath in patients with COPD when compared with placebo, although melatonin does not seem to improve lung function or exercise capacity (62854). Another small clinical trial shows that taking melatonin 3 mg daily in combination with rehabilitative exercise training improves exercise capacity, health status, and quality of life when compared with placebo. The distance walked in 6 minutes was increased by 46 meters (113221).
• Cluster headache. It is unclear if oral melatonin prevents cluster headaches. Details: A very small clinical study in adults with cluster headaches shows that taking melatonin orally 10 mg every evening for 14 days might reduce the frequency of episodic cluster headaches when compared with placebo (1127). However, 2 mg at bedtime does not seem to be effective (9702).
• Cognitive impairment. Oral melatonin has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in adults 70 years and older with mild cognitive impairment shows that taking two capsules containing melatonin 5 mg, docosahexaenoic acid (DHA) 720 mg, eicosapentaenoic acid (EPA) 286 mg, vitamin E 16 mg, soy phospholipids 160 mg, and L-tryptophan 95 mg (IBSA Farmaceutici) before bedtime for 12 weeks modestly improves cognitive function and sensitivity to smells when compared with placebo. The observed improvement on the mini-mental state examination (MMSE) scale falls below the score generally considered to be indicative of true changes in cognitive function, and may not be clinically significant. Also, it is not known if any potential benefit is due to melatonin, other ingredients, or the combination (62847).
• Colorectal cancer. It is unclear if oral melatonin is beneficial for colorectal cancer prevention. Details: Population research suggests that any history of melatonin use is associated with an approximate 20% reduction in the incidence of colorectal cancer, especially rectal cancer, in individuals aged 60 years and older (106291).
• Contraception. Although there has been interest in using oral melatonin for contraception, there is insufficient reliable information about the clinical effects of melatonin for this use.
• Coronary artery bypass graft (CABG) surgery. It is unclear if oral melatonin is beneficial for recovery from CABG surgery. Details: Clinical research shows that taking melatonin perioperatively during CABG surgery reduces the length of stay in the ICU by about 0.5 days and modestly reduces levels of creatine kinase-MB when compared with placebo. However, there was no effect on the length of hospital stay or levels of cardiac troponin-I, C-reactive protein, or erythrocyte sedimentation rate. Oral melatonin 3 mg was provided the night before and morning of surgery, as well as at bedtime for 3 days after surgery (109699).
• Coronavirus disease 2019 (COVID-19). Preliminary clinical studies suggest that oral melatonin may reduce disease severity in patients with COVID-19, although some conflicting findings exist. Details: A meta-analysis of mainly small and preliminary randomized clinical trials in patients with COVID-19 shows that taking melatonin improves clinical outcomes when compared with placebo. However, the clinical outcomes differed between individual trials, and included specific symptoms, hospital discharge, removal from quarantine, and survival. Dosing also varied, with doses of 2-24 mg daily in 1-4 divided doses for 6-14 days. There was no effect of melatonin on C-reactive protein levels or oxygen saturation (109695). Individual clinical trials have been conducted in hospitalized and/or non-hospitalized patients with mild to severe COVID-19. One clinical trial in outpatients with mild to moderate COVID-19 shows that taking melatonin 10 mg daily modestly reduces time to symptom resolution and quality of life improvement when compared with placebo (109462). However, it is unclear if any beneficial effects are clinically meaningful. In patients hospitalized and receiving standard care for mild to moderate COVID-19, a small clinical trial shows that taking melatonin 3 mg three times daily for 14 days reduces the mean time to hospital discharge by approximately 3.5 days when compared with placebo. Also, persistent symptoms of cough, dyspnea, and fatigue after 14 days occurred in only 0% to 8% of patients taking melatonin, compared with 15% to 30% of those taking placebo. However, there was no difference in the number of patients with other symptoms, including fever, myalgia, chill, and headache (106300). The validity of this study is limited by its high attrition rate. Another small clinical trial in patients hospitalized with COVID-19 shows that taking melatonin (Norm Life Vanatonin Melatonin) 3 mg nightly for 7 days does not reduce symptoms or prevent ICU admission or death when compared with standard care alone (106295). The low dose and short duration of use in this study might have played a role in the lack of benefit. Melatonin has also been evaluated in patients hospitalized for severe COVID-19. One large single-center preliminary clinical trial shows that taking melatonin 10 mg daily reduces the incidence of thrombosis at day 17 and the incidence of sepsis at day 11 when compared with standard care alone. Death occurred in approximately 17% of patients taking placebo, compared with 1% of those taking melatonin (106289). Another preliminary clinical trial in patients in the ICU for severe COVID-19 shows that taking melatonin (Danna Pharmaceutical Company, Iran) 5 mg twice daily for 7 days results in mortality and invasive mechanical ventilation rates of 67% and 51.4%, respectively, compared with 94% and 70.9% in patients given standard care only. There were also modest improvements in the time to improvement of clinical status and lengths of stay in the hospital and ICU (110297). The validity of these studies is limited by a lack of blinding.
• Delirium. It is unclear if oral melatonin is beneficial for preventing delirium in hospitalized patients; the available research is conflicting. Details: Research is conflicting on whether melatonin reduces the incidence of delirium. One meta-analysis of 10 clinical trials shows that melatonin reduces the incidence of delirium in critically ill patients in the intensive care unit (ICU) by 21% when compared with a control, usually placebo (109696). However, other meta-analyses of 14 small clinical and observational studies of hospitalized patients show that taking melatonin does not reduce the incidence of delirium when compared with control (105003,112440). Melatonin might be less beneficial in non-acute medical patients when compared with postoperative patients or those in the ICU (105003). There is also a lack of consensus within the available research on whether melatonin reduces the duration of delirium in hospitalized patients. One meta-analysis of 10 clinical trials shows that melatonin does not reduce the duration of delirium (109696). However, a meta-analysis of 2 small, randomized controlled trials shows that taking melatonin 3-5 mg daily for 5 or more days reduces the duration of delirium by approximately 2 days when compared with placebo (112051). This analysis is limited by substantial heterogeneity and a lack of dose-response evaluation. Most studies in these analyses have used doses of 0.5-10 mg daily for up to 14 days, although one study used a very high single dose of 50 mg/kg (105003,105891,107809,108949,109696,112051). Some research suggests that melatonin may be beneficial for patients undergoing cardiac procedures. A subgroup analysis of one meta-analysis including 3 small studies suggests that melatonin reduces the incidence of delirium in patients in cardiovascular care units, but not in the general ICU population (112440). Two large clinical studies in the meta-analysis suggest that, in older patients admitted to the ICU after acute heart failure or percutaneous coronary intervention (PCI), taking melatonin 3 mg once daily for up to 7 days is associated with a 27% incidence of delirium, compared with a 37% to 40% incidence with placebo (107809,108949). Additionally, a small clinical study in patients undergoing coronary artery bypass graft (CABG) surgery suggests that taking prolonged-release melatonin (Webber Naturals) 3 mg twice before surgery and twice after surgery reduces the occurrence of delirium over the next 48 hours when compared with placebo (105891). The validity of this study is limited by a high risk of bias due to insufficient blinding and incomplete outcome data. Additionally, a small clinical study shows that receiving melatonin 3 mg through a nasogastric tube once at 9 pm, followed by a 0.5 mg hourly maintenance dose for 6 hours during the overnight period, does not reduce delirium or improve sleep when compared with placebo in patients in the ICU that are being weaned off sedatives and mechanical ventilation (104997).
• Diabetes. Most research shows that oral melatonin is beneficial for improving glycemic control. However, it is unclear if oral melatonin is beneficial in patients with type 2 diabetes. Details: Most research on the use of melatonin for glycemic control has been conducted in mixed populations, such as those with schizophrenia, metabolic syndrome, nonalcoholic steatohepatitis (NASH), or perimenopause (103490,106294,106298). Two recent meta-analyses of clinical research in these populations show that taking melatonin modestly reduces fasting glucose and insulin, insulin resistance, and glycated hemoglobin (HbA1c), and improves insulin sensitivity (106294,106298). The most common doses of melatonin used were 3 -10 mg for 8-24 weeks; however, 10 mg may be more effective (106294,106298). This contrasts with an earlier meta-analysis showing only modest beneficial effects of melatonin on fasting glucose levels and insulin sensitivity (103490). Research on the use of melatonin in patients with type 2 diabetes is limited. One small clinical trial in patients with type 2 diabetes show that taking melatonin (NatureMade) 6 mg daily for 8 weeks does not improve glycemic control (104368). However, this trial may have been underpowered to detect a difference. Another very small study in adults with type 2 diabetes shows that taking melatonin 3 mg daily before bed for 7 days increases absolute glucose level at breakfast on day 7 and the glycemic difference between post-dinner on day 6 and pre-breakfast on day 7 but does not change most measures of glycemic variability including mean glucose levels, pre-prandial glucose levels, and post-prandial glucose levels compared with placebo (112441).
• Diabetic neuropathy. It is unclear if oral melatonin is beneficial for improving pain in patients with diabetic neuropathy. Details: A clinical study in patients with painful diabetic neuropathy living in Iran shows that taking melatonin 3 mg nightly for 1 week and then 6 mg nightly for 7 weeks, in conjunction with pregabalin 150 mg daily seems to reduce pain and sleep interference to a greater degree than placebo and pregabalin (105895).
• Dry mouth. It is unclear if oral melatonin is beneficial for dry mouth caused by radiation treatment. Details: A small clinical study in patients with head and neck cancer undergoing chemoradiation shows that taking melatonin 20 mg orally at bedtime and using 10 mL of melatonin 0.2% oral gargle 15 minutes before each radiation session does not delay the onset or reduce the incidence of grade 2 dry mouth when compared with placebo. However, the incidence of grade 3 dry mouth is delayed by approximately 16 days (96314).
• Dysmenorrhea. It is unclear if oral melatonin is beneficial for dysmenorrhea. Details: A small clinical trial shows that taking melatonin 10 mg nightly before bed during the week of menstruation has a statistically significant effect on pain severity when compared with placebo. However, the pain reduction was not considered clinically significant (106301).
• Dyspepsia. It is unclear if oral melatonin is beneficial for dyspepsia in adults. Details: Preliminary clinical research shows that taking melatonin 5 mg nightly for 12 weeks improves dyspeptic symptoms in individuals with functional dyspepsia. However, the benefit seems to be decreased in patients with prior Helicobacter pylori infection (62456).
• Endotracheal intubation-associated adverse effects. It is unclear if oral melatonin is beneficial for endotracheal intubation-related hemodynamic effects. Details: Clinical research shows that taking immediate-release melatonin (Healthy Hey Nutrition) 6 mg, 2 hours prior to the induction of anesthesia, is as effective as clonidine 0.2 mg for attenuating the hemodynamic response to laryngoscopy and tracheal intubation (103483). It is not known if melatonin prevents other adverse effects associated with endotracheal intubation.
• Endometriosis. It is unclear if oral melatonin reduces endometriosis-related pain. Details: Preliminary clinical research shows that taking melatonin 10 mg daily for 8 weeks reduces pain by about 39% and analgesic use by about 46%, as well as pain during menstruation, intercourse, and evacuation, when compared with placebo in adults with endometriosis (89503). Other clinical research in adults with endometriosis shows that taking melatonin 20 mg orally daily does not improve pain scores or reduce pain during intercourse, urination, or defecation when compared with placebo (111464). However, the study may have been inadequately powered to detect a difference between groups.
• Epilepsy. It is unclear if oral melatonin is beneficial for epilepsy in children or adults. Details: There is some low-quality evidence that taking melatonin 3 mg at bedtime for 3 months might reduce the frequency and duration of both nocturnal and daytime seizures in children aged 2-15 years with epilepsy (9699,9745,9746,62785). Also, taking melatonin 1.5 mg before bed for 3 months might reduce the seizure severity in children with epilepsy that is not successfully controlled with other treatment (62754). Furthermore, taking fast-release melatonin 10 mg daily for 3 weeks seems to reduce diurnal seizure frequency in both adults and children aged 9 years and up with intractable epilepsy (88291). However, taking melatonin might not be beneficial for seizure reduction in younger children. In infants and children aged 3 months to 2 years with infantile epileptic spasms syndrome receiving adrenocorticotrophic hormone (ACTH) and magnesium sulfate, adding on melatonin 3 mg daily for 2 weeks before bedtime does not reduce spasm frequency or improve response rate when compared with placebo (113223). Limited research has also assessed melatonin as an adjunct therapy in adults with seizure disorders. A small clinical study in adults with epilepsy involving generalized onset motor seizures that recurred within the last three days shows that adding melatonin 3 mg before bed to therapy with valproate 20 mg/kg in two divided doses daily for 8 weeks results in 82% of patients having at least a 50% reduction in seizure frequency, compared with only 53% of patients in the group taking valproate and placebo. Adding melatonin may also improve seizure severity (105006). However, other clinical research in adults under valproic acid treatment for idiopathic generalized tonic-clonic seizures alone shows that taking melatonin 3 mg before bed for 8 weeks modestly reduces seizure severity, but not frequency (110299).
• Fibromyalgia. It is unclear if oral melatonin is beneficial for this condition. Details: Preliminary clinical research shows that taking melatonin 3-5 mg daily for up to 60 days may decrease the severity of pain and stiffness, as well as the number of painful joints, in people with fibromyalgia when compared with placebo (9701,62797).
• Gastroesophageal reflux disease (GERD). It is unclear if oral melatonin is beneficial for GERD. Details: Clinical research shows that taking melatonin 3 mg daily at bedtime for 8 weeks may improve symptoms of GERD, including heartburn and epigastric pain. However, taking omeprazole 20 mg twice daily seems to be more effective (62723).
• Helicobacter pylori. It is unclear if oral melatonin is beneficial for Helicobacter pylori eradication. Details: One very small clinical study shows that taking melatonin 5 mg twice daily in combination with omeprazole 20 mg twice daily for 21 days improves ulcer healing rates when compared with omeprazole alone in individuals with H. pylori-associated gastroduodenal ulcers (62803).
• Heart failure. It is unclear if oral melatonin is beneficial for heart failure. Details: A small clinical study in adults with stable NYHA class II or III heart failure with reduced ejection fraction (HFrEF) and a left ventricular ejection fraction (LVEF) below 40%, shows that taking melatonin 10 mg orally every evening for 24 weeks improves a composite score reflecting all-cause mortality, hospitalization for exacerbation, and quality of life when compared with placebo. Melatonin also attenuates an increase in serum B-type natriuretic peptide levels, but does not affect LVEF or left ventricular end-diastolic or end-systolic diameter (108950).
• Irritable bowel syndrome (IBS). It is unclear if oral melatonin is beneficial for IBS. Details: In patients with IBS who also have poor sleep, taking melatonin 3 mg at bedtime for 2 weeks seems to decrease symptoms of IBS-related abdominal pain and increase the rectal pain threshold when compared with placebo. However, taking melatonin does not seem to influence stool frequency or consistency, bloating, mood, sleep, or overall quality of life (13112). In other small clinical studies, taking melatonin 3 mg at bedtime for 8 weeks decreased severity and frequency of pain, reduced bloating, improved bowel habits, decreased extracolonic symptoms such as headache, heartburn and nausea, and improved overall quality of life when compared with placebo (15216,62410). However, other clinical research shows that melatonin does not significantly affect the amount of time needed for food to travel through the colon in patients with IBS (62500). Also, one small clinical study shows that taking melatonin 3 mg in the morning and 5 mg in the evening for 6 months improves abdominal pain, bloating, and bowel habits in 50% to 70% of postmenopausal patients with constipation-predominant IBS when compared with placebo. However, beneficial effects were reduced in patients with diarrhea-predominant IBS (89510). Other clinical research in patients with IBS shows that taking melatonin 6 mg orally daily for 8 weeks improves IBS symptom severity scores, abdominal pain scores, and bloating scores, when compared with placebo. These results were not different between those with or without sleep disorders at baseline (112055). The large number of endpoints, many with inconsistent results, in these studies makes it difficult to draw conclusions.
• Ischemia-reperfusion injury. It is unclear if intravenous or intracoronary melatonin is beneficial for ischemia-reperfusion injury. Details: A meta-analysis of 9 low-quality clinical trials in patients with myocardial ischemia-reperfusion injury shows that giving melatonin in doses of 2-50 mg by intravenous or intracoronary injection within 2.5-3.5 hours of ischemia onset improves left ventricular ejection fraction and reduces the infarct size, but does not improve left ventricular end-diastolic or end-systolic volumes, when compared with control. Also, giving melatonin orally for up to 12 weeks does not improve cardiac function. The patients in this study experienced injury as a result of an ST-elevation myocardial infarction, ischemic heart disease, acute coronary syndrome, or coronary heart disease (108946).
• Kidney failure. It is unclear if oral melatonin is beneficial for improving mood and quality of life in patients on hemodialysis. Details: A small clinical trial in patients undergoing hemodialysis shows that taking immediate-release melatonin 3 mg (Puritans Pride, USA) for 3 months modestly improves depression, anxiety, and quality of life when compared with placebo. After treatment, 73.1% and 57.7% of those taking placebo had severe depression and anxiety, respectively, when compared with 22.2% and 14.8% of those taking melatonin (110291).
• Kidney transplant. It is unclear if oral melatonin is beneficial for improving post-transplant kidney function. Details: A small clinical study in patients that have received kidney transplants shows that taking melatonin 3 mg daily for an average of 25 days does not affect urine volume or kidney function, as measured by the blood urea nitrogen over creatinine (BUN/Cr) ratio, when compared with placebo (103693).
• Lung cancer. It is unclear if melatonin is beneficial in patients with early stage non-small cell lung cancer (NSCLC). Details: A clinical study in patients who have undergone complete surgical resection of early stage NSCLC shows that taking melatonin 20 mg daily for 1 year does not improve 2-5 year disease-free survival, pain, anxiety, fatigue, or quality of life when compared with placebo (105894). The validity of these findings is limited by a high study withdrawal rate.
• Melasma. Although there has been interest in using oral melatonin for melasma and other causes of hyperpigmentation, there is insufficient reliable information about the clinical effects of melatonin for these conditions.
• Menopausal symptoms. It is unclear if oral melatonin is beneficial for improving symptoms of menopause; evidence is conflicting. Details: A meta-analysis of 3-5 clinical studies in patients with menopausal symptoms shows that taking melatonin does not seem to improve vasomotor or psychological symptoms, but may modestly improve physical symptoms, when compared with placebo (105897). This analysis is limited due to inconsistent evidence and some risk of bias within the included studies. Studies included in the meta-analysis used melatonin 3 mg daily for 3-12 months alone or in combination with soy isoflavones 80 mg or fluoxetine 20 mg (11806,62840,105897). In contrast, a small study in adults with menopausal symptoms shows that taking melatonin 3 mg daily for 12 weeks improves climacteric symptoms, anxiety, depressive symptoms, sleep quality, and menopausal quality of life and decreases luteinizing hormone and follicle stimulating hormone levels but does not change uterine volume, endometrial thickness, or estradiol levels when compared with placebo (112443).
• Metabolic syndrome. It is unclear if oral melatonin is beneficial for this condition. Details: Preliminary clinical research in adults with metabolic syndrome shows that taking melatonin 5 mg nightly for 2 months reduces systolic and diastolic blood pressure, as well as low-density lipoprotein (LDL) cholesterol levels, when compared to baseline (62795). The validity of these findings is limited by the lack of a comparator group.
• Multiple sclerosis (MS). It is unclear if oral melatonin is beneficial for MS. Details: A small clinical study in patients with relapsing-remitting MS (RRMS) receiving interferon-beta once weekly shows that taking melatonin 3 mg daily for 12 months does not affect relapse rate, disability, brain lesions, fatigue, or depression when compared with placebo (99345). This small study may not have been adequately powered to detect a difference between groups.
• Myocardial infarction (MI). The benefits of administering oral or intravenous melatonin immediately after an MI are unclear. Details: A meta-analysis of 5 small clinical studies in patients after MI shows that oral or intravenous melatonin, used in conjunction with medical reperfusion, is associated with modestly lower troponin levels and modestly higher left ventricular ejection fraction when compared with control (105889). One clinical study included in this analysis that evaluated patients with ST-segment elevation myocardial infarction (STEMI) shows that intravenous administration of melatonin 51.7 mcmol over 60 minutes immediately prior to percutaneous coronary intervention, combined with a bolus intracoronary dose of melatonin 8.6 mcmol administered within 60 seconds after restoration of blood flow to the infarcted artery, does not reduce myocardial infarct size when compared with placebo. However, subgroup analyses suggest that the timing of melatonin administration after symptom onset may alter its effects (96324).
• Neonatal encephalopathy. It is unclear if oral or intravenous melatonin is beneficial for neonates with encephalopathy. Details: A meta-analysis of two small clinical studies in term or late preterm infants with neonatal encephalopathy who are receiving therapeutic hypothermia shows that receiving melatonin 5 mg/kg intravenously daily for 3 days, or 10 mg/kg orally daily for 5 days, does not reduce mortality when compared with hypothermia alone, although a nonsignificant trend towards a reduction was noted (104994). One of those small studies in term infants with neonatal encephalopathy also shows that receiving adjunct oral melatonin treatment results in fewer seizures and less white matter abnormalities when compared with hypothermia alone (99333).
• Nocturnal enuresis. It is unclear if oral melatonin is beneficial for reducing nighttime wettings. Details: Preliminary clinical research shows that taking melatonin 5 mg nightly before bedtime for 3 months does not reduce the number of wet beds when compared with placebo in children with nighttime wettings (nocturnal enuresis) (62824).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral melatonin is beneficial for NAFLD. Details: A meta-analysis of clinical research, as well as individual clinical trials, show that taking melatonin 6-18 mg daily for 4-56 weeks improves some liver indices, but not others (62853,88285,103484,103485). Overall, taking melatonin seems to modestly reduce levels of alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT). However, there is no effect on alanine aminotransferase (ALT) and levels of aspartate aminotransferase (AST) slightly increased (103485). One small clinical study shows that taking melatonin (Nature Made, USA) 6 mg daily for 12 weeks has a small benefit on systolic and diastolic blood pressure, body mass index (BMI), abdominal circumference, and liver enzymes, but not plasma lipid levels, when compared with placebo (103484). Larger studies are needed to determine the effect of melatonin in this population.
• Obesity. It is unclear if melatonin is beneficial for improving weight loss. Details: A meta-analysis of clinical research shows that taking melatonin up to 10 mg daily, usually for 4-24 weeks, modestly reduces body weight when compared with placebo. However, there was no effect on body mass index (BMI) or waist circumference. Also, the studies included in the analysis were not limited to overweight or obese individuals. Populations included those with metabolic syndrome, nonalcoholic steatohepatitis (NASH), schizophrenia, polycystic ovary syndrome (PCOS), and others, as well as postmenopausal adults (106288). A small clinical trial in overweight or obese individuals shows that although taking melatonin 3 mg daily for 12 weeks modestly reduces waist circumference and body fat mass when compared with placebo, there is no effect on body weight or BMI (106290).
• Oral mucositis. Most research shows that melatonin does not prevent or reduce the severity of oral mucositis in patients with head and neck cancer receiving radiation and chemotherapy. It is unclear if oral or topical melatonin is beneficial in patients with other types of cancer. Details: A meta-analysis of seven clinical trials including patients undergoing chemotherapy or radiotherapy shows that melatonin does not reduce the rate of oral mucositis when compared with a control, usually placebo (109697). Although a small clinical study in patients with head and neck cancer undergoing radiation and chemotherapy with cisplatin shows that melatonin delays the onset of severe mucositis by 16 days when compared with placebo (96314), a meta-analysis shows that melatonin does not reduce the rate of oral mucositis in patients with head and neck cancer (109697). A sub-analysis in one meta-analysis suggests that taking melatonin, usually 20 mg daily, reduces the rate of oral mucositis by 53% in patients with cancer types other than head and neck (109697). Most studies investigating the effect of melatonin have used oral melatonin 20 mg at bedtime. However, in one study, 10 mL of melatonin 0.2% oral gargle was also used 15 minutes before radiation (96314). In another, swishing with 10 mL of a melatonin 3% gel mouthwash for 2 minutes and then swallowing, starting 2-3 days before radiotherapy and continuing until 1-4 weeks after the end of radiotherapy, was used (105893). Melatonin has also been investigated for oral mucositis severity. Although some individual research disagrees (96314), a meta-analysis of three clinical trials shows that melatonin does not reduce the severity of oral mucositis when compared with placebo. However, the form of melatonin provided in these studies was heterogeneous, including oral, gargle, and gel formulations (96314,105893,109697).
• Osteopenia. It is unclear if oral melatonin is beneficial for improving bone mineral density. Details: A small clinical study in postmenopausal adults with osteopenia shows that taking melatonin 3 mg nightly for 1 year increases tibia thickness by 2.2% and volumetric bone mineral density (BMD) in the spine by 3.6% when compared with placebo. However, the BMD of other skeletal sites was not impacted. Additionally, a 1 mg melatonin dose was not beneficial (99334).
• Osteoporosis. Although there has been interest in using oral melatonin for osteoporosis, there is insufficient reliable information about the clinical effects of melatonin for this condition.
• Pain (acute). It is unclear if oral melatonin is beneficial for acute pain. Details: Clinical research in patients undergoing laparoscopic cholecystectomy shows that taking melatonin 6 mg two hours before induction with propofol reduces the number of patients requiring intraoperative fentanyl to 10%, compared with 35% of those taking placebo (106299). Also, preliminary clinical research in preterm infants also given standard treatments shows that oral melatonin (Syrup Trunap, Brio Bliss Life Science Pvt. Ltd) 20 minutes prior to retinopathy of prematurity screening, is not inferior to 24% sucrose for reducing pain (110295). However, the effect of sucrose itself is inconclusive and this study is limited by a lack of blinding. Also, it is unclear if melatonin is beneficial for other causes of acute pain.
• Pain (chronic). It is unclear if melatonin is beneficial for most causes of chronic pain. Details: A meta-analysis of 5 clinical studies shows that taking melatonin 3-12 mg daily for up to 12 weeks modestly reduces chronic pain when compared with placebo (103692). However, it is difficult to draw clinical conclusions from this analysis, as it pools the effects observed in various types of chronic pain, including migraine, burning mouth syndrome, endometriosis, and irritable bowel syndrome (IBS).
• Periodontitis. Small clinical studies suggest that oral melatonin may improve some measures of periodontitis severity. Details: A meta-analysis of 7 small clinical trials in patients with periodontitis treated with subgingival instrumentation to remove calculus and bacterial biofilms shows that adding oral melatonin in doses of 3-10 mg daily improves probing depth, clinical attachment loss, and gingival index when compared with instrumentation alone (108953).
• Polycystic ovary syndrome (PCOS). It is unclear if melatonin is beneficial for PCOS. Details: A prospective cohort study in patients with PCOS has found that taking melatonin (Armonia Fast, Nathura) 2 mg before bedtime for 6 months increases follicle-stimulating hormone and the total number of menstrual cycles from approximately 2.5 to 4 when compared to baseline (96313). The validity of this study is limited by its observational nature and the lack of a comparator group. Additionally, a small clinical study in patients with PCOS shows that taking melatonin 6 mg daily for 8 weeks does not affect insulin levels, fasting blood glucose, lipid levels, or weight, but might modestly reduce testosterone levels, when compared with placebo (105887). This study may have not been adequately powered to detect differences between groups.
• Postoperative nausea and vomiting (PONV). It is unclear if melatonin is beneficial for reducing PONV. Details: A small clinical trial shows that taking melatonin (Nature Made, USA) 3 mg, 5 mg, or 10 mg, one hour prior to lumbar discectomy surgery does not reduce postoperative nausea when compared with placebo (110294).
• Postoperative pain. It is unclear if melatonin is beneficial for reducing pain postoperatively. Details: Three meta-analyses, as well as most individual clinical studies, show that taking melatonin in addition to standard therapy modestly alleviates pain and reduces analgesic use after surgery when compared with placebo (62471,62512,62551,62743,88293,88294,103488,103691,103692,105892)(110294,111462). However, any benefit is likely to be small and may not be clinically relevant (103488,109701,111462). Melatonin has been used in doses of 1-10 mg daily for a duration of 1-21 days, usually starting the night before surgery (62471,62512,62743,103488,103691,105892,110294,111462). This research is limited by poor methodology, as well as the heterogeneity of the included studies. The studies evaluated melatonin across a wide variety of surgeries, including abdominal hysterectomy, cataract surgery, cesarean section, prostatectomy, lumbar laminectomy, lumbar discectomy, laparoscopic cholecystectomy, wisdom teeth extraction, and corrective jaw surgery.
• Postoperative recovery. It is unclear if oral melatonin improves the rate of recovery after surgery. Details: In females undergoing total abdominal hysterectomy, taking extended-release melatonin 5 mg, 90 minutes before surgery, shortens hospital stay to a mean of 2.7 days, compared with 3.4 days for placebo (108945).
• Postoperative sleep disturbance. It is unclear if melatonin is beneficial for improving postoperative sleep disturbance. Details: A meta-analysis of randomized trials in adults undergoing anesthesia for surgery shows that taking melatonin 5-12 mg orally or sublingually or ramelteon 8 mg orally daily for 1-6 days does not improve sleep scores or sleep time when compared with placebo or no intervention (112052). In addition, a small clinical trial shows that taking melatonin (Nature Made) 5 mg each night before bed for 4 weeks, starting 2 weeks after surgery for orthopedic trauma, does not reduce postoperative sleep disturbance when compared with placebo. All patients were also given education related to sleep hygiene (110293).
• Postural tachycardia syndrome (POTS). It is unclear if melatonin is beneficial for POTS. Details: Preliminary clinical research in patients with POTS shows that taking a single dose of melatonin 3 mg reduces sitting and standing heart rate, after 2 and 4 hours, when compared with placebo. However, melatonin does not appear to affect blood pressure or orthostatic symptoms (88292). It is unclear if melatonin is beneficial when taken as more than a single dose.
• Pre-eclampsia. It is unclear if oral melatonin reduces the severity of pre-eclampsia. Details: A small clinical trial in patients with pre-eclampsia shows that taking sustained-release melatonin 10 mg with vitamin B6 10 mg three times daily, starting during recruitment and continuing until delivery, attenuates the need to increase the dose of antihypertensive medication on certain days, but does not affect overall pre-eclampsia severity, when compared with control (99341).
• Prostate cancer. Oral melatonin has only been evaluated in combination with medication; its effect when used alone is unclear. Details: One small clinical study in patients with metastatic prostate cancer that is refractory or resistant to treatment with the luteinizing hormone-releasing hormone (LHRH) analogue triptorelin shows that taking melatonin 20 mg daily in combination with intramuscular triptorelin injected every 28 days can decrease levels of prostate-specific antigen (PSA) and growth factors for prostate cancer when compared to baseline (7255). The validity of these findings is limited by the small study size and lack of a comparator group.
• Pruritus. Small clinical trials suggest that oral melatonin might be beneficial for some types of pruritus. Details: One small clinical trial in patients with pruritus due to various types of chronic liver disease shows that taking melatonin 10 mg nightly for 2 weeks modestly reduces the severity, frequency, and extent of pruritus when compared with placebo (106297). Another small clinical study in patients undergoing hemodialysis shows that taking melatonin 10 mg daily for 2 weeks reduces the severity of pruritus and reduces the affected body area when compared with placebo (104996).
• Radiation dermatitis. It is unclear if topical melatonin is beneficial for radiation-related dermatitis. Details: In females with breast cancer, a small clinical study shows that applying a specific melatonin emulsion cream (Praevoskin, PraevoMed GmbH) twice daily during radiation treatment and continuing for another 2 weeks results in fewer cases of grade 1 or 2 acute radiation dermatitis when compared with placebo (99336). In contrast, another clinical trial in patients with breast cancer shows that applying a cream providing melatonin 25 mg and dimethylsulfoxide 150 mg twice daily during and for 3 weeks after radiation treatment does not improve quality of life or breast symptoms at the end of treatment when compared with placebo. However, there was a modest reduction in breast symptoms over time (110298). Other preliminary clinical research in adults receiving radiation for breast cancer shows that applying melatonin cream 25 mg/gram twice daily throughout radiation therapy does not improve radiation dermatitis scores or reduce the need for adjunctive treatment when compared with placebo (112056).
• Rapid eye movement sleep behavior disorder (RBD). It is unclear if oral melatonin is beneficial for RBD. Details: One very small clinical study shows that taking melatonin 3 mg before bed for 4 weeks increases the likelihood of muscle atonia during rapid eye movement (REM) sleep in patients with RBD when compared with placebo (62762). The validity of this finding is limited by the small study size.
• Restless legs syndrome (RLS). It is unclear if oral melatonin is beneficial for RLS. Details: One very small clinical study shows that taking melatonin 3 mg before bedtime does not improve symptoms of RLS and may actually worsen motor symptoms in individuals with RLS when compared with baseline (62753). The validity of this finding is limited by the small study size and lack of a comparator group.
• Rheumatoid arthritis (RA). It is unclear if oral melatonin is beneficial for RA. Details: A small clinical study in patients with RA shows that taking melatonin 6 mg daily for 12 weeks does not affect disease activity or erythrocyte sedimentation rate (ESR) when compared with placebo (105890).
• Sarcoidosis. It is unclear if oral melatonin is beneficial for this condition. Details: One very small clinical study shows that taking melatonin 20 mg daily for one year, followed by 10 mg daily for another year, improves lung function and skin lesions in patients with chronic sarcoidosis when compared with baseline (62435). The validity of this finding is limited by the small study size and lack of a comparator group.
• Schizophrenia. It is unclear if oral melatonin is beneficial for schizophrenia or for attenuating the adverse effects associated with antipsychotic medications. Details: Some clinical research shows that taking melatonin orally 3 mg each evening for 8 weeks reduces the weight gain and increased waist circumference associated with olanzapine when compared with placebo. It also seems to improve some symptoms of schizophrenia (88296). Other clinical research shows that taking a specific brand of slow-release melatonin (Cronocaps, Productos Medix) 5 mg each evening for 8 weeks reduces adverse effects from second generation antipsychotics, such as increased diastolic blood pressure and waist circumference, when compared with placebo. However, it does not seem to improve symptoms of schizophrenia (88300).
• Seasonal affective disorder (SAD). It is unclear if oral melatonin is beneficial for SAD. Details: Some preliminary clinical research shows that oral melatonin, 0.25-2 mg taken daily for 3 weeks, may decrease winter depression symptoms in patients with SAD (10670,62308). However, sublingual melatonin 0.5 mg daily for 6 days does not appear to improve this condition (62388). Reasons for these discrepancies may include the duration of treatment, route of administration, or the severity of SAD at baseline.
• Smoking cessation. It is unclear if oral melatonin is beneficial in patients trying to quit smoking. Details: One very small clinical study shows that taking melatonin 0.35 mg as a single oral dose 3.5 hours after initiation of nicotine withdrawal in smokers seems to reduce subjective symptoms of anxiety, restlessness, irritability, depression, and cigarette craving over the next 10 hours when compared with baseline (2424). The validity of these findings is limited by the small study size and lack of a comparator group.
• Sepsis. It is unclear if oral melatonin is beneficial for sepsis in neonates or adults. Details: There is conflicting research about the effect of melatonin on neonatal sepsis. While some preliminary research in Egypt shows that giving a single dose of melatonin 20 mg in addition to antibiotics reduces sepsis severity, another more recent study did not find a difference in outcomes between groups receiving antibiotics only or antibiotics with melatonin (99339,99340). In adults with early septic shock given standard care, a small clinical trial shows that taking melatonin 50 mg daily for 5 days increases the number of ventilator-free days by 6.9 and the number of vasopressor-free days by 2.6. ICU and hospital lengths of stay were reduced by 5.25 and 6.9 days, respectively. However, after 28 days there was no significant difference in the mortality rate, the number of patients requiring ventilation or renal replacement therapy, or the number of patients recovered from organ dysfunction (106296). Intravenous melatonin has also been investigated. A small clinical trial in patients with severe sepsis shows that a continuous infusion of melatonin, 60 mg over 24 hours, for 5 days following post-surgical sepsis diagnosis modestly reduces sepsis severity when compared with placebo. Hospital stay was reduced by approximately 5.2 days in patients given melatonin; however, it is unclear if this difference is statistically significant (110300).
• Stabbing headache. Although there has been interest in using oral melatonin for stabbing headaches, there is insufficient reliable information about the clinical effects of melatonin for this condition.
• Stress. It is unclear if oral melatonin is beneficial for stress reduction. Details: Preliminary clinical research shows that taking melatonin 3 mg one hour prior to stress modestly improves memory accuracy during a laboratory-induced stressful situation when compared with placebo (62509).
• Tardive dyskinesia. It is unclear if oral melatonin is beneficial for this condition. Details: One small clinical study shows that taking melatonin orally 10 mg daily for 6 weeks decreases symptoms by 24% to 30% in patients with tardive dyskinesia when compared with placebo (7082). However, other small clinical studies show that taking melatonin 2-20 mg daily for 4-12 weeks does not reduce abnormal, involuntary movement in patients with tardive dyskinesia when compared with placebo (62146,62825).
• Tension headache. It is unclear if oral melatonin is beneficial for reducing the frequency of tension headaches. Details: A small clinical study in patients with chronic tension headache shows that taking a specific melatonin supplement (Melaxen) 3 mg nightly for 30 days seems to reduce headache severity and reduce the median number of days with a headache by 6 when compared with baseline (104998). The validity of this finding is limited by the lack of a control group.
• Tinnitus. It is unclear if oral melatonin is beneficial for improving tinnitus intensity or severity. Details: Some clinical research shows that taking melatonin 3 mg nightly for one month reduces tinnitus intensity and improves the quality of sleep in individuals with chronic tinnitus when compared with placebo. The effect seems to be greatest in men, those who have not received prior treatment for tinnitus, and those with a history of noise exposure (62820). Other clinical research shows that taking melatonin 3 mg daily for 3 months is more effective for reducing tinnitus severity than sertraline 50 mg daily (97447). However, other clinical research shows that taking melatonin 3 mg nightly for 30-40 days does not significantly reduce tinnitus intensity when compared with placebo, although the effects might be significant when melatonin is combined with sulpiride or sulodexide (62469,62614).
• Traumatic brain injury (TBI). It is unclear if oral melatonin is beneficial for children who have experienced a concussion. Details: A small clinical study in children ages 8-18 years who have experienced a concussion shows that taking melatonin 3 mg or 10 mg one hour before bedtime for 28 days does not improve persistent post-concussive symptoms when compared with placebo (103690). One small observational study in children in the same age group who have experienced a concussion within 14 days has found that receiving a prescription for melatonin is not associated with improved symptoms and recovery at 15-35 days after concussion (105001). The validity of these findings is limited by small study size and short duration of follow-up.
• Ulcerative colitis. Oral melatonin may be modestly beneficial for reducing symptoms or sustaining remission in patients using the medication mesalazine. Details: A small clinical study shows that taking melatonin 5 mg daily in combination with mesalazine 1 gram twice daily for 12 months may help to sustain remission in patients with ulcerative colitis when compared with mesalazine alone (62821). Another small clinical trial in patients with mild to moderate ulcerative colitis shows that taking melatonin 3 mg daily for 3 months modestly improves overall symptoms, some measures of quality of life, and levels of fecal calprotectin when compared with placebo. However, there was no effect on other markers of inflammation, such as C-reactive protein and erythrocyte sedimentation rate (106303). More evidence is needed to rate melatonin for these uses.

(Read more about MELATONIN)

POSSIBLY EFFECTIVE

• Cognitive function. Oral L-theanine may improve some aspects of cognitive function. It is unclear if using L-theanine in conjunction with caffeine can enhance the effects of either ingredient. Details: A single dose of L-theanine 100 mg seems to improve vigilant attention, reducing error rates in cognitive tests when compared with placebo (91747). However, taking L-theanine (Suntheanine, Taiyo Kagaku) 200 mg daily for 4 weeks does not improve verbal fluency, memory, motor speed, or executive function in an adult population, although it may moderately improve verbal fluency in a subgroup of people with lower cognitive function at baseline (101986). When L-theanine is combined with caffeine, a meta-analysis and multiple individual clinical studies show that the combination improves alertness, as well as accuracy during a test that requires switching attention between different tasks, but does not improve reaction time (38116,91750,96335,96336). Some research also shows that L-theanine plus caffeine improves cognitive performance and reduces task-induced fatigue when compared with baseline and placebo. However, it is unclear if this is due to the individual ingredients or the combination (38116,96335,96336). Some research suggests that the combination is no better than either individual ingredient alone (91747,96335,96336).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Age-related cognitive decline. It is unclear if oral L-theanine, taken continuously or as a single dose, improves cognition in older adults. Details: A small clinical study in healthy, Japanese adults aged 50-69 years shows that taking a specific product (Suntheanine; Taiyo International.) containing L-theanine 101 mg daily after breakfast for 12 weeks does not improve mini-mental state exam (MMSE) scores when compared with placebo. However, a single-dose analysis from this study shows that administration of L-theanine 101 mg may improve the quality of working memory and reaction times during a cognitive function test when compared with placebo (108553). Patients were permitted to consume polyphenol-rich beverages during the study period; however, consumption was not documented, limiting the validity of this finding.
• Alzheimer disease. Although there is interest in using oral theanine for Alzheimer disease, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Anxiety. It is unclear if oral L-theanine is beneficial in patients with anxiety. Results of clinical research are conflicting. Details: A preliminary clinical study shows that taking a single dose of a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg does not reduce experimentally-induced anticipatory anxiety when compared with placebo (12188). However, another preliminary clinical study in healthy adults with stress-related anxiety shows that taking L-theanine 200 mg daily for 4 weeks reduces anxiety scale scores and sleep disturbance when compared with placebo (101986).
• Attention. It is unclear if oral theanine improves attention. Details: A small clinical study in healthy males shows that taking a single dose of L-theanine 200 mg improves selective attention similar to a single dose of caffeine 160 mg (96337). However, other small clinical studies in adults show that taking L-theanine 100-400 mg does not improve most measures of attention, especially sustained attention or attention in executive control tasks, but doses of 100-200 mg may improve performance in simple attentional tasks when compared with placebo (96338,111396). Some of these studies suggest that taking L-theanine with caffeine appears to provide more benefit than either individual ingredient alone (96337,96338).
• Attention deficit-hyperactivity disorder (ADHD). Oral L-theanine seems to improve some aspects of ADHD, including cognition and sleep. Details: Some preliminary clinical research in children with ADHD shows that taking a one-time dose of L-theanine 2.5 mg/kg increases cognition scores, but does not improve results on sustained attention or inhibitory control tests, when compared with placebo. Taking L-theanine with caffeine 2 mg/kg also increases cognition scores and improves performance on a sustained attention test, but does not improve inhibitory control, when compared with placebo (104141). Other preliminary clinical research in males aged 8-12 years with ADHD shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg orally twice daily for 6 weeks increases the percent of time spent in restful sleep by about 5% and decreases the number of bouts of nocturnal activity by about 6 when compared with placebo (91744).
• Cancer. Although there is interest in using oral theanine for cancer, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Chemotherapy-induced diarrhea. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with colon cancer shows that taking L-cystine 700 mg and L-theanine 280 mg (Ajinomoto Co. Inc.) orally once daily, starting one week before chemotherapy with TS-1 (Taiho Pharmaceutical) and continuing for 28 days, increases the rate of therapy completion by 49%, reduces the incidence of diarrhea by 37%, reduces appetite loss by 33%, and improves the reported tolerability of chemotherapy when compared with chemotherapy alone (96334). However, this combination does not appear to be beneficial in patients with gastric cancer, or in those with colorectal cancer receiving 4 courses of capecitabine-based adjuvant chemotherapy. (96334,101985).
• Cognitive impairment. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One very small clinical study in adults with mild cognitive impairment shows that taking a product containing L-theanine 120 mg and green tea extract 720 mg (LGNC-07, LG Household & Health Care, Ltd) orally twice daily after meals for 16 weeks modestly improves memory and attention when compared with baseline. However, taking this product does not appear to improve memory and attention when patients with self-reported memory problems, but without mild cognitive impairment, are also considered (96339).
• Depression. It is unclear if oral L-theanine is beneficial in patients with depression. Details: A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku Co. Ltd.) 250 mg at bedtime for 8 weeks reduces symptoms and improves sleep quality when compared to baseline in individuals with mild major depressive disorder (MDD) (96331). The validity of these findings is limited by the lack of a comparator group. Another small clinical study in adults with MDD shows that taking L-theanine 200 mg daily with sertraline for 6 weeks reduces depression symptoms and increases remission rates but does not improve treatment response rates when compared with sertraline and placebo (112278). The validity of these effects is limited by the small sample size and short study duration. Additionally, it is unclear if the reduction in depressive symptoms is clinically significant.
• Erythema. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in healthy females with self-perceived skin sensitivity shows that taking a specific supplement containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne) daily for 8 weeks reduces facial pigmentation when compared to baseline (111399). The validity of this finding is limited by a lack of a placebo group. It is unclear if these effects are due to L-theanine, other ingredients, or the combination.
• Generalized anxiety disorder (GAD). It is unclear if oral L-theanine is beneficial for reducing anxiety in people with GAD. Details: One small clinical study in adults with GAD shows that taking L-theanine 225 mg twice daily for 4 weeks, then 450 mg twice daily for 4 weeks, in conjunction with prescribed antidepressants, does not reduce anxiety scores when compared with antidepressants and placebo (104976).
• Hypertension. Although there is interest in using oral theanine for hypertension, there is insufficient reliable information about the clinical effects of theanine for this condition.
• Influenza. Oral L-theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research shows that taking a combination of green tea catechins (THEA-FLAN 90S, Ito-en Co.) 378 mg, standardized to contain epigallocatechin gallate 270 mg and L-theanine (Suntheanine, Taiyo Kagaku) 210 mg daily for 5 months reduces the risk of developing clinically diagnosed influenza when compared with placebo. However, the combination does not seem to prevent laboratory-confirmed influenza infection (54021).
• Insomnia. It is unclear if oral L-theanine is beneficial for insomnia. Details: A very small clinical study in young healthy adults with sleep quality worsened by caffeine intake shows that taking L-theanine 50 mg (Suntheanine, Taiyo Kagaku Co. Ltd) once 10 minutes before bedtime suppresses caffeine-induced elevations in wake after sleep onset time but does not improve parameters of sleep quality including sleep onset latency, sleep time, or number of times waking after sleep onset when compared with placebo (112275). L-theanine has also been studied in combination with other ingredients. A small clinical study in adults with insomnia or disturbed sleep patterns shows that a specific product (RLX2; LiveLife Biosciences AG) containing L-theanine 50 mg and a specific casein peptide, alpha-s1-casein tryptic hydrolysate, 150 mg, taken one hour before bedtime for 4 weeks, increases sleep duration by 45 minutes and improves habitual sleep efficiency and daytime dysfunction when compared with baseline (108556). Another very small clinical study in healthy adults shows that taking a combination product containing tryptophan, glycine, magnesium, tart cherry powder, and L-theanine 2 hours before bedtime decreases sleep onset latency and increases total sleep duration, leading to better sleep efficiency and reduced morning sleepiness, when compared with placebo (111184). Another combination product containing L-theanine, ashwagandha, and saffron (InnerCalm, Arbonne), taken daily for 8 weeks, seems to improve sleep quality when compared to baseline (111399). However, the validity of this finding is limited by a lack of a control group. It is unclear if the effects described above are due to L-theanine, other ingredients, or the combination.
• Obsessive-compulsive disorder (OCD). It is unclear if oral L-theanine is beneficial for OCD. Details: A small clinical study in adults with OCD shows that taking L-theanine 100 mg twice daily for 10 weeks with fluvoxamine reduces OCD symptoms, particularly obsessive symptoms, and increases the proportion of patients with a complete response to treatment but does not improve compulsive symptoms, partial response rates, or remission rates when compared with placebo and fluvoxamine (112276).
• Postoperative recovery. Oral theanine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study of adults with esophageal cancer undergoing esophagectomy shows that taking theanine 280 mg and cystine 700 mg daily, staring 4 days before surgery and continued for 13 days after surgery, does not improve measures of physical activity but does improve exercise tolerance and some measures of quality of life when compared with placebo (111400). It is unclear if these findings are due to theanine, cystine, or the combination.
• Schizophrenia. It is unclear if oral L-theanine is beneficial in patients with schizophrenia; the available evidence is limited and conflicting. Details: One small preliminary clinical study in adults with schizophrenia or schizoaffective disorder shows that taking L-theanine (Biosynergy) 200 mg orally twice daily for 8 weeks along with antipsychotic medications improves positive symptoms, anxiety, and general psychopathology symptoms, such as poor impulse control and disorientation, when compared with placebo. However, theanine does not improve general disease severity, negative symptoms, depression, cognitive function, extrapyramidal side effects, or quality of life (96341). In contrast, two small clinical studies show that taking L-theanine 400 mg (Suntheanine, BioSynergy Health Alternatives) with antipsychotics and with or without pregnenolone 50 mg daily for 8 weeks reduces negative symptoms, general psychopathology symptoms, and anxiety when compared with placebo in patients with schizophrenia or schizoaffective disorder. However, there were no improvements in positive schizophrenia symptoms, extrapyramidal side effects, or symptoms of depression (97923,112277). The inconsistency of results might be due to the small study sizes and the subjectivity of the outcomes measured.
• Stress. It is unclear if oral L-theanine is beneficial in patients with stress. Details: One very small clinical study shows that taking L-theanine 200 mg prior to a stress-inducing exam reduces tension-anxiety and may prevent blood pressure increases caused by psychological stress when compared with placebo (91746). Other preliminary clinical research in pharmacy students shows that taking theanine 200 mg twice daily for one week prior, and then for the first 10 days of a pharmacy practice period, decreases subjective stress scores when compared with placebo (91745). Another small clinical study in healthy young adults shows that drinking a beverage containing L-theanine 200 mg alone or combined with L-arginine 50 mg after a psychological stressor reduces stress, as measured by salivary alpha-amylase activity, when compared with placebo. The combination of L-arginine and L-theanine did not differ from L-theanine alone, suggesting that the combination does not act synergistically to reduce markers of stress (110393). However, not all research has been positive. A small clinical study shows that taking a specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg induces subjective feelings of tranquility in relaxed people, but not those with experimentally-induced anticipatory anxiety, when compared with placebo (12188). Also, a small, clinical crossover study in healthy, moderately stressed adults shows that taking a single dose of a specific product (Alphawave; Ethical Naturals) containing L-theanine 200 mg prior to a stress-inducing exam does not improve anxiety at any time point when compared with placebo (108554). Due to the single-dose nature of this study, the effects of continued administration of this product are unclear. L-theanine has also been evaluated in combination with other ingredients. A small clinical study in adults with stress shows that taking a specific combination product (Mg-Teadiola, Sanofi-Aventis Group), containing green tea extract 125 mg (providing 50 mg L-theanine), magnesium 150 mg, vitamin B6 0.2 mg, vitamin B9 0.1 mg, vitamin B12 1.25 mcg, and rhodiola 222 mg, orally once daily for 28 days modestly improves stress and anxiety scores when compared with placebo. Improvements in stress scores, but not anxiety scores, appear to persist at 28 days after treatment completion (108672). It is unclear if any effects are due to L-theanine, other ingredients, or the combination.
• Tourette syndrome. It is unclear if oral L-theanine is beneficial in children with Tourette syndrome. Details: A small, nonblinded clinical study in children aged 4-17 years with untreated Tourette syndrome or with chronic tic disorder and associated symptoms of anxiety shows that taking a liquid nutritional supplement providing L-theanine 200 mg and vitamin B6 2.8 mg daily for 2 months improves scores on the Yale Global Tic Severity Scale, but does not reduce anxiety, when compared with patients receiving psychoeducation (108555). This study may have been inadequately powered to detect a difference between groups. More evidence is needed to rate theanine for these uses.

(Read more about THEANINE)

EFFECTIVE

• Vitamin C deficiency. Oral or intramuscular vitamin C is effective for preventing or treating vitamin C deficiency. Details: Administering vitamin C orally or intramuscularly prevents and treats vitamin C deficiency, including scurvy. Vitamin C administration can reverse complications of scurvy within 2 days to 3 weeks (4844). In newborns with transient tyrosinemia due to vitamin C deficiency, oral or intramuscular vitamin C can correct this condition (15).

POSSIBLY EFFECTIVE

• Anemia of chronic disease. Oral vitamin C seems to improve markers of anemia in patients on hemodialysis. Details: Meta-analyses of clinical research in hemodialysis patients with anemia shows that treatment with vitamin C 200-300 mg three times weekly for 3-6 months increases hemoglobin levels by approximately 0.9 grams/dL, increases transferrin saturation by about 8%, and decreases the required recombinant human erythropoietin dose by 17 U/kg weekly when compared with standard care (83447,83475).
• Atrial fibrillation. Oral and intravenous vitamin C seems to help prevent atrial fibrillation after cardiac surgeries. Details: Meta-analyses of clinical research show that taking vitamin C prior to and after cardiac surgery reduces the risk of postoperative atrial fibrillation by 27% to 53%. Most studies administered vitamin C at doses of 1-2 grams orally daily for 1-3 days prior to cardiac surgery, followed by 1-2 grams in two divided doses daily for 4-5 days after cardiac surgery. Some studies provided vitamin C intravenously at similar doses, but oral vitamin C seems to be more effective (91233,96703,96705). Despite these findings, a meta-analysis of clinical research conducted only in the U.S. does not support the benefit of vitamin C for reducing postoperative atrial fibrillation (96703). These differences may be related to lifestyle factors such as nutrition, as well as differences in hospital treatments. Vitamin C has also been studied in combination with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with evidence of benefit (90701).
• Bowel preparation. Powdered vitamin C is approved for use as part of a polyethylene glycol-based bowel preparation for colonoscopy. Details: Clinical research shows that treatment with 2 liters of oral solution containing polyethylene glycol (PEG) plus vitamin C achieves a similar quality of bowel cleansing as treatment with 4 liters of PEG when administered on the evening prior to colonoscopy or when administered in a split-dose regimen. Patients given 2 liters of PEG plus vitamin C solution also have better adherence and experience fewer adverse events, such as nausea, vomiting, or abdominal bloating, compared to patients treated with 4 liters of PEG solution without vitamin C (90413,90415,90420,90424,90428). This treatment also appears to be effective and tolerable in elderly patients aged 60-79 years, including those with poor bowel habits and a high number of comorbidities (108085). Other clinical research in older adults undergoing bowel preparation for colonoscopy also shows that taking 1 liter of PEG plus vitamin C (CleanViewAL, Taejoon Pharm) results in similar quality of bowel cleansing overall and per segment with similar tolerability and adverse effects as sodium picosulfate 170 mL plus magnesium citrate or oral sulfate solution alone (111297,112476). The most common PEG plus vitamin C preparation used in clinical research is MoviPrep (Norgine BV), which contains macrogol 3350 100 grams, sodium sulfate 7.5 grams, sodium chloride 2.7 grams, potassium chloride 1 gram, vitamin C 4.7 grams, and sodium ascorbate 5.9 grams per liter of solution (90413,90415,90424). In the U.S., MoviPrep is approved by the Food and Drug Administration (FDA) for bowel preparation prior to a colonoscopy.
• Cataracts. Dietary and supplemental intake of vitamin C may reduce the risk of developing cataracts. Details: Population research suggests that people with the highest total intake of vitamin C have about a 19% reduced risk of developing cataracts when compared with those with the lowest total intake, with the most benefit observed for nuclear cataracts (96711). Additionally, another observational study shows that higher supplemental intake of vitamin C over 10 years is associated with a 60% reduction in the incidence of nuclear and cortical cataracts (4208). Other population research suggests that individuals with the highest blood levels of vitamin C have a 33% lower odds of developing age-related cataract, but any benefit is limited to Asian populations (90944). An umbrella review of meta-analyses also shows that dietary intake of vitamin C is associated with a 27% lower odds of cataract development (112095). However, a prospective clinical study shows that a combination of vitamin C, vitamin E, and beta-carotene does not prevent age-related loss of vision from cataracts in well-nourished people with an average supplementation duration of 6.3 years (7304).
• Common cold. Oral high-dose vitamin C might modestly shorten and reduce cold symptoms; however, taking vitamin C prophylactically does not seem to prevent the development of a cold. Details: There is substantial controversy about the effectiveness of vitamin C for treating the common cold (1969,1989,7100,9835,9836). The majority of evidence shows that taking high doses of vitamin C orally might decrease the duration of cold symptoms by 1-1.5 days in some patients (1966,1967,1968,1987,6458,7102,9832,83487). However, other studies have found no effect with doses up to 3 grams daily (9833). A meta-analysis of clinical research in healthy children and adults shows that taking vitamin C 1-4 grams daily for one week to 5 months reduces cold severity by 13%, limits absences from daily activities, and improves the duration of severe symptoms, but does not reduce the duration of mild symptoms, when compared with placebo (113665). Vitamin C has also been investigated for preventing the common cold. A meta-analysis of clinical research suggests that vitamin C supplementation decreases the incidence of cold in individuals exposed to physical stress, but not in the general population (83487). Other research suggests vitamin C may be more effective for treating cold symptoms in children than in adults. Also, there may be a dose-dependent response; doses of at least 2 grams daily seem to work better than 1 gram doses (9834). Taking vitamin C supplements prophylactically does not decrease the risk of catching a cold (1966,1967,1968,1987,3042,6458,7101,9832). Dietary intake of vitamin C also does not seem to affect the risk of getting a cold (10780).
• Complex regional pain syndrome. Most research shows that taking oral vitamin C after a distal radius (i.e. wrist) fracture or surgery seems to reduce the risk of developing complex regional pain. However, it is unclear if oral vitamin C is beneficial in reducing the risk of complex regional pain in other orthopedic surgeries. Details: Although some research has found no benefit in patients with distal radius (i.e. wrist) fractures (90411,96702), most clinical research shows that taking vitamin C 500 mg daily, and possibly doses of up to 1500 mg daily, for 45-50 days beginning immediately after fracture can reduce the risk of developing complex regional pain syndrome (2045,16302,96700,96706). Reasons for discrepancies are unclear but might relate to differences in diagnostic criteria for complex regional pain syndrome (96702). Research in patients undergoing various orthopedic surgeries has also shown benefit with the use of vitamin C for the prevention of complex regional pain syndrome; however, some findings are conflicting. (90422,108076,115613). One meta-analysis of clinical research in patients undergoing ankle, foot, or wrist surgery shows that taking vitamin C 500-1000 mg for 42-50 days following surgery reduces the rate of complex regional pain syndrome, and may improve pain following ankle or foot surgery, when compared with placebo (108076). The validity of these findings is limited by the high heterogeneity of included trials. An additional meta-analysis of clinical research in patients undergoing a broader variety of orthopedic surgery types (i.e., ankle, foot, knee, shoulder, wrist) shows that taking vitamin C 500 to 1500 mg does not reduce the incidence of complex regional pain syndrome (115613). The reasons for these discrepant findings are unclear but may relate to the inclusion of a wide range of orthopedic surgeries.
• Exercise-induced respiratory infections. High-dose oral vitamin C seems to reduce the risk of respiratory infections associated with strenuous exercise. Details: Some preliminary clinical research suggests that prophylactic use of vitamin C in doses of 600 mg to 1 gram daily for 3-8 weeks before heavy physical exercise, such as a marathon, might prevent upper respiratory infections that sometimes follow heavy exercise (9831,83370). More recently, high doses of vitamin C have been studied. A large clinical study in army recruits undergoing basic military training shows that taking vitamin C 6 grams daily for one month reduces the odds of getting a cold by 20% when compared with placebo (102975).
• Hypercholesterolemia. Oral vitamin C seems to reduce lipid levels in patients with hypercholesterolemia. Details: A meta-analysis of clinical research in patients with hypercholesterolemia shows that taking vitamin C 500 mg daily for at least 4 weeks reduces low-density lipoprotein (LDL) cholesterol by about 8 mg/dL and reduces triglycerides by about 20 mg/dL when compared with control (83445).
• Hypertension. Oral vitamin C seems to modestly reduce blood pressure in patients with hypertension, but some evidence is conflicting. Details: Vitamin C seems to modestly reduce systolic blood pressure (SBP), without meaningful effects on diastolic blood pressure (DBP) (2044,9822,13162,83483,102974). A meta-analysis of 13 clinical trials in patients with hypertension, with or without other comorbidities, shows that taking a median dose of vitamin C 500 mg daily for 8 weeks reduces SBP but not DBP by about 5 mmHg. Some of the studies used vitamin C in combination with other supplements, such as vitamin E and magnesium. When studies assessing vitamin C alone were analyzed, the magnitude of reduction in SBP decreased (83483). A newer meta-analysis of small clinical studies in patients with essential hypertension shows that taking vitamin C 200 mg or more daily reduces SBP by about 4 mmHg and DBP by about 2 mmHg (102974). However, this newer analysis omitted numerous relevant studies and included studies with normotensive patients and those without an adequate control, limiting the validity of its findings. In contrast, a network meta-analysis of small, low-quality clinical studies comparing five different vitamins in adults with essential hypertension shows that vitamin C does not reduce SBP, DBP, mean 24-hour SBP, mean 24-hour DBP, or heart rate when compared with placebo and when indirectly compared with vitamin B2, vitamin D, vitamin E, and folic acid. However, the included studies were of low quality and high heterogeneity, particularly in dosing, limiting the validity of the results (113668).
• Laser skin resurfacing. Topical vitamin C seems to reduce erythema occurring after cosmetic laser skin resurfacing procedures intended to reduce scars and wrinkles. Details: There is some evidence that an aqueous formulation of topical vitamin C can decrease the degree and duration of erythema following cutaneous carbon dioxide laser resurfacing for scar and wrinkle removal (1959).
• Lead toxicity. Dietary vitamin C seems to lower concentrations of lead in the blood. Details: Observational research has found that consuming more vitamin C from dietary sources is associated with lower blood concentrations of lead. People who consumed at least 340 mg of vitamin C daily as part of the diet had lower blood lead levels than those who consumed less than 100 mg vitamin C daily (3097,3098,3099).
• Nitrate tolerance. Oral vitamin C might prevent nitrate tolerance in some patients. Details: Small clinical studies show that taking vitamin C orally seems to prevent the development of nitrate tolerance in patients taking sublingual nitroglycerin. There is some evidence that short-term vitamin C supplementation can prevent tolerance to the vasodilatory effects of nitrates (1441,1961).
• Postoperative pain. Oral or intravenous vitamin C might prevent acute postoperative pain following certain surgeries. It is unclear if vitamin C reduces chronic postoperative pain. Details: A meta-analysis of 7 small clinical studies in adults undergoing elective surgery shows that receiving perioperative vitamin C, either as 1 gram orally, 2-3 grams intravenously, or 50 mg/kg intravenously, modestly reduces acute pain and opioid requirements for up to 24 hours when compared with control (105457). Most surgeries were laparoscopic and included cholecystectomy, colectomy, hysterectomy; two non-laparoscopic surgeries included uvulopalatopharyngoplasty with tonsillectomy and major abdominal surgery (90418,99840,105457). A meta-analysis of clinical trials in adults undergoing noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, kidney transplantation) shows that administering perioperative vitamin C, either orally or intravenously, reduces postoperative intravenous morphine requirements at 2, 24, and 48 hours after surgery and improves pain scores at 2, 6, and 24 hours after surgery when compared with placebo. The dose of vitamin C did not appear to impact outcomes. However, when only laparoscopic surgeries are included, perioperative vitamin C does not improve pain or morphine use when compared with placebo (108087). Use of vitamin C perioperatively has also been evaluated in other surgery types with generally similar outcomes. A moderate-sized clinical study in adults undergoing total hip arthroplasty shows that intravenous vitamin C 3 grams perioperatively reduces 24-hour post-operative morphine use and subjective pain scores when compared with placebo; however, these improvements do not appear to be clinically significant (115500). The validity of these results is limited by a short follow-up period. Additionally, a small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces pain 24, 48, and 72 hours after surgery when compared with control (113664). However, a moderate-sized clinical study in adults undergoing transurethral resection of a bladder tumor under general anesthesia shows that administering intravenous vitamin C 1 gram after induction of anesthesia reduces the incidence and severity of catheter-related bladder discomfort immediately after surgery and at 1 and 2 hours postoperatively, but not 6 hours, when compared with placebo. Further, vitamin C does not reduce postoperative pain scores or analgesic requirements when compared with placebo (111645). Vitamin C has also been evaluated for reducing chronic pain after surgery. Clinical research in patients undergoing surgery for foot or ankle trauma shows that taking vitamin C 500 mg orally twice daily postoperatively for 6 weeks reduces pain scores when compared with placebo at 2 weeks and 6 weeks. The mean total amount of diclofenac used for pain relief over the 6-week period is also reduced, from 5.7 grams with placebo to 3.4 grams with vitamin C (102131).
• Wrinkled skin. Topical vitamin C might reduce the appearance of existing wrinkles. Details: Topical preparations containing vitamin C seem to improve the appearance of wrinkled skin. Some evidence shows that vitamin C 3% applied for 12 weeks might reduce facial wrinkles (14008). A small clinical study shows that applying a dissolving microneedle patch containing vitamin C 5.6% every 4 days for 12 weeks to crow's feet on one side of the face reduces wrinkles when compared to control treatment applied on the other side of the face (98780). Other clinical research in females aged 30-60 years shows that applying an oil-soluble cream containing the vitamin C derivative tetra-isopalmitoyl ascorbic acid 1%, 2%, or 3% to the periorbital area twice daily for 8 weeks reduces visual wrinkle grading when compared with placebo. A dose analysis shows greater improvements in wrinkle parameters, average wrinkle depth, and mean depth with the lower concentration, while greater improvements in maximum roughness and maximum depth are observed with the higher concentration (108072). This study only included individuals defined as having Fitzpatrick skin type III or IV; it effects on other skin types is unclear. Preparations containing vitamin C in combination with other ingredients have also been investigated. A small low-quality trial in females with moderately photodamaged and hyperpigmented facial skin shows that applying a moisturizer with vitamin C 30%, vitamin E, and coenzyme Q10 once daily in the morning, along with applying retinol 0.5% once daily or once every other day for 12 weeks, seems to improve skin tone, photodamage, and wrinkles when compared to baseline (99085). In another small trial, a topical preparation containing vitamin C 10% as L-ascorbic acid along with acetyl tyrosine, zinc sulfate, sodium hyaluronate, and bioflavonoids (Cellex-C High Potency Serum) applied to photo-aged facial skin for 3 months improves fine and coarse wrinkling, yellowing and sallowness, roughness, and skin tone when compared with placebo (6155). It is unclear if the beneficial effects of these products are due to vitamin C, other ingredients, or the combination.

POSSIBLY INEFFECTIVE

• Acute bronchitis. Oral vitamin C doesn't seem to improve symptoms of acute bronchitis. Details: A clinical study in adults with acute bronchitis shows that taking vitamin C orally 500 mg on day 1, then 250 mg on days 2 through 5 (similar to an azithromycin regimen) doesn't seem to have any effect on quality of life or bronchitis duration when compared with azithromycin (9827).
• Asthma. Oral vitamin C doesn't seem to prevent asthma or improve lung function. Details: Although some observational research has found that some patients with asthma might have lower serum vitamin C levels (5873), other observational research found that increased dietary vitamin C intake is not associated with a reduced risk of asthma or improved lung function (15006,34567). In addition, clinical research shows that supplemental intake of vitamin C does not reduce asthma symptoms, improve lung function, or reduce the use of inhaled steroids in asthma patients (90409).
• Atherosclerosis. Oral vitamin C does not seem to reduce the progression of atherosclerosis. Details: A clinical study shows that taking a specific combination product containing slow-release vitamin C 250 mg and vitamin E 136 IU (CellaVie, Ferrosan A/S) twice daily modestly slows the 3-year progression of atherosclerosis of the carotid artery in males, but not females. This result persisted at a 6-year follow-up of this study (1918,10473). However, when this form of vitamin C is used alone, it does not slow the 3-year progression of atherosclerosis of the carotid artery (1918).
• Bladder cancer. Oral vitamin C does not reduce the risk of bladder cancer or mortality from bladder cancer. Details: Epidemiological research has found that supplemental vitamin C intake is not associated with mortality rate in patients with bladder cancer (9839). A secondary analysis of a large clinical trial, the Physicians' Health Study II, in healthy men aged at least 50 years also shows that taking vitamin C 500 mg daily alone or with vitamin E 400 IU daily for up to 10 years does not reduce the risk of developing bladder cancer or bladder cancer-related deaths when compared with placebo (90097).
• Cardiovascular disease (CVD). Oral vitamin C does not seem to be beneficial for either primary or secondary CVD prevention. Details: Vitamin C does not seem to be beneficial for primary prevention of CVD. Some population research has found that higher supplemental vitamin C or dietary vitamin C has been associated with a reduced risk of developing CVD (10358,14108,109779), while other observational research has found no benefit (34566,10358,14108). However, meta-analyses of clinical research in healthy patients show that vitamin C supplementation does not prevent CVD or coronary heart disease when compared with control (97308,104025). In 2004, the American Heart Association stated that current evidence does not justify use of antioxidants such as vitamin C for reducing the risk of CVD (12142). Evidence is also negative for secondary prevention in people with coronary heart disease. Population studies have found that higher serum vitamin C was associated with no effect or decreased CVD mortality from CVD (3910,5878). A meta-analysis of two large clinical trials shows that vitamin C supplementation does not reduce CVD events or CVD mortality when compared with control (97308).
• Colorectal cancer. Oral vitamin C does not seem to prevent colorectal cancer. Details: Population research has found that dietary vitamin C intake is not associated with a reduced risk of developing colon cancer. When total vitamin C intake from food and supplements is considered, there is a modest association (34600). However, most clinical trials show that supplemental vitamin C, alone or along with other antioxidants, does not reduce the risk of colorectal cancer development, colorectal cancer or adenoma recurrence, or colorectal cancer-related mortality (34580,34581,34594,90097,90089,92903).
• Fetal and premature infant mortality. Oral vitamin C does not seem to prevent neonatal death. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of neonatal death (83472,96707).
• Fractures. Oral vitamin C does not seem to improve fracture healing. Details: Clinical research shows that taking vitamin C 500 mg daily for 50 days following an acute distal radial fracture does not improve physical function, symptoms, or healing rates when compared with placebo (90411).
• Helicobacter pylori. Oral vitamin C does not seem to improve eradication of H. pylori. Details: Most clinical research shows that treatment with vitamin C, alone or in combination with vitamin E, does not improve the eradication rate of H. pylori when taken with a standard eradication regimen when compared with the eradication regimen alone (83476,90094).
• Hereditary motor and sensory neuropathy. Oral vitamin C does not seem to improve neuropathy in these patients. Details: In a meta-analysis of five studies in patients with Charcot-Marie-Tooth disease type 1A, taking vitamin C 1-4 grams orally daily for 1 year did not improve neuropathy when compared with placebo (99084). Continuing vitamin C 4 grams daily for 2 years also does not improve neuropathy in these patients (90419).
• Interferon-related retinopathy. Oral vitamin C does not seem to improve retinopathy associated with interferon therapy. Details: A small clinical study in patients with chronic hepatitis C receiving interferon therapy shows that taking vitamin C 600 daily orally does not seem to reduce the risk of retinopathy from interferon therapy when compared with control (10355).
• Leukemia. Oral vitamin C does not seem to reduce the risk of leukemia or mortality from leukemia. Details: A large clinical trial in men aged at least 50 years shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing leukemia or leukemia-related deaths when compared with placebo (90097).
• Low birth weight. Oral vitamin C does not seem to reduce the risk of infants being born with a low birth weight. Details: Meta-analyses of clinical research show that maternal use of oral vitamin C alone or with other supplements does not reduce the risk of giving birth to infants with low birth weight when compared with control (83450,83472).
• Lung cancer. Oral vitamin C does not seem to reduce the risk of lung cancer. Details: Two meta-analyses of clinical research suggest that taking vitamin C, alone or in combination with vitamin E, does not reduce the incidence of lung cancer or lung cancer-related mortality (34528,34632). Also, a clinical study in females shows that taking supplemental vitamin C 500 mg daily, with or without vitamin E and beta carotene, is associated with an INCREASED risk of lung cancer when compared with placebo (34580). However, another large epidemiological cancer screening trial with a mean follow-up of over 12 years suggests that moderate dietary intake of vitamin C around 500 mg daily is protective against lung cancer, but higher doses of vitamin C might increase the risk of lung cancer (112096).
• Melanoma. Oral vitamin C does not seem to reduce the risk of melanoma. Details: Clinical research shows that taking vitamin C 500 mg daily, alone or along with vitamin E 400 IU daily, for up to 10 years does not reduce the risk of developing melanoma or melanoma-related deaths when compared with placebo in men aged at least 50 years (90097).
• Miscarriage. Oral vitamin C does not seem to reduce the risk of miscarriage. Details: A meta-analysis of clinical research shows that taking vitamin C alone or with other supplements does not reduce the risk of miscarriage when compared with control (94820).
• Overall mortality. Oral vitamin C does not reduce overall mortality. Details: Although population research suggests that higher dietary intake and higher plasma vitamin C levels are associated with a reduced risk of mortality from all causes (3910,109779), vitamin C supplementation does not seem to affect overall mortality. Meta-analyses of clinical research show that taking vitamin C supplements does not reduce overall mortality when compared with control (34622,111641). Clinical studies of vitamin C used in combination with vitamin E, beta carotene, and/or selenium and zinc, also show no benefit for overall mortality (9817,14109).
• Pancreatic cancer. Oral vitamin C does not seem to prevent pancreatic cancer. However, it is unclear if intravenous vitamin C is beneficial for treatment of pancreatic cancer. Details: Observational research has found that increased dietary vitamin C intake is associated with up to a 30% reduced risk of pancreatic cancer (99083,99086). However, clinical research shows that supplemental vitamin C 500 mg daily does not reduce the risk of pancreatic cancer in females (34580). Also, taking vitamin C in combination with beta-carotene plus vitamin E does not reduce the risk of pancreatic cancer (12185,34581). While research suggests oral vitamin C may not prevent pancreatic cancer, intravenous vitamin C is being explored in the treatment of pancreatic cancer. A small, open-label clinical study in adults with stage IV pancreatic ductal adenocarcinoma shows that administration of intravenous vitamin C 75 grams three times weekly throughout each cycle of chemotherapy increases median overall survival and progression free survival by approximately 8 months and 2 months, respectively, when compared with chemotherapy alone (115499). The validity of these results is limited by potential overestimation of treatment effects, influenced by small sample size, differences in chemotherapy doses, and early study termination.
• Pre-eclampsia. Oral vitamin C does not seem to prevent pre-eclampsia. Details: Despite some early positive research in high-risk pregnancies, the majority of meta-analyses and clinical studies show that taking vitamin C alone or with vitamin E or other supplements does not reduce the risk of pre-eclampsia when compared with control. There is even some concern that vitamin C supplementation may increase the risk of gestational hypertension (3236,83450,83472,83474,96707).
• Preterm labor. Oral vitamin C does not seem to prevent preterm labor. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of preterm labor when compared with control (83450,83472,96707).
• Prostate cancer. Oral vitamin C does not seem to prevent prostate cancer. However, it is unclear if intravenous vitamin C is beneficial for the treatment of prostate cancer. Details: A large-scale clinical study (The SU.VI.MAX study) shows that a combination of vitamin C 120 mg, vitamin E (alpha-tocopherol) 30 mg, beta-carotene 6 mg, selenium 100 mcg, and zinc 20 mg, taken daily for an average of 8 years, does not reduce the risk of prostate cancer overall. However, it might reduce the risk of prostate cancer in those who have normal PSA levels. It does not seem to be beneficial for reducing the risk of prostate cancer in patients with PSA levels above 3 mcg/L (14135). Another large scale study (Physician's Health Study II) shows that taking vitamin C 500 mg daily for an average of 8 years does not significantly reduce the risk of prostate cancer when compared with placebo (16708). Similarly, results from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial seem to show that supplemental or dietary intake of vitamin C does not reduce the risk of prostate cancer when compared to individuals not taking vitamin C (14124). While research suggests oral vitamin C may not prevent prostate cancer, intravenous vitamin C is being explored in the treatment of prostate cancer. A small clinical study in adults with metastatic castration-resistant prostate cancer shows that administration of intravenous vitamin C 1 gram/kg twice weekly in combination with docetaxel for up to 24 weeks does not reduce prostate-specific antigen (PSA) by 50% or more when compared with docetaxel alone (115611). This study may have been underpowered to show a difference between groups.
• Radiation dermatitis. Topical vitamin C does not seem to prevent radiation dermatitis in cancer patients. Details: A small clinical study shows that applying a 10% vitamin C solution does not appear to protect from radiation dermatitis when applied to the scalps of patients treated with radiation for intracranial tumors (789).
• Small for gestational age (SGA). Oral vitamin C does not seem to reduce SGA. Details: Meta-analyses of clinical research show that taking vitamin C alone or with other supplements does not reduce the risk of small for gestational age birth when compared with control (83450,83472).
• Stillbirth. Oral vitamin C does not seem to prevent stillbirth. Details: Meta-analyses of clinical research show that maternal use of vitamin C alone or with other supplements does not reduce the risk of stillbirth when compared with control (83472,96707).

LIKELY INEFFECTIVE

• Coronavirus disease 2019 (COVID-19). Oral vitamin C, even at high doses, does not seem to speed recovery from COVID-19 in non-hospitalized patients. Most studies show that oral or intravenous vitamin C given to patients hospitalized with COVID-19 does not improve organ function or survival, but the evidence is conflicting. It is unclear whether vitamin C is beneficial for long COVID. Details: A clinical study in adult outpatients with confirmed COVID-19 shows that taking oral vitamin C (ascorbic acid) 8000 mg in 2-3 divided doses daily, alone or with zinc gluconate 50 mg daily, for 10 days does not reduce symptom severity when compared with standard care (104450). The study was terminated prior to complete enrollment due to futility and apparent lack of effect from vitamin C and/or zinc supplementation. Limitations of this study include a lack of placebo control and blinding. Additionally, this study has been criticized for methodologic concerns (106624). Another small clinical trial in adult outpatients with confirmed COVID-19 shows that taking vitamin C 1000 mg daily for 14 days does not improve symptoms or quality of life when compared with placebo (109462). Vitamin C has also been evaluated in patients hospitalized with COVID-19. A very large analysis of two multinational clinical studies in critical and non-critical adults hospitalized with COVID-19 shows that administering intravenous vitamin C 50 mg/kg every 6 hours for 96 hours does not improve organ support-free days or survival and has a high probability of futility and worsened outcomes when compared with placebo (113666). Individual prospective and retrospective studies in critically ill patients hospitalized with COVID-19 in various countries have found that administering vitamin C, either enterally as 500-1000 mg daily or intravenously as 8-24 grams daily or 50 mg/kg daily, does not significantly reduce in-hospital or short-term mortality, hospital length of stay, or end-organ failure when compared with control groups receiving standard care alone. Additionally, all but one study found no change in the need for mechanical ventilation (105458,105465,106937,106938,108075,108079,108081). However, a meta-analysis and some small individual studies have found that vitamin C is modestly beneficial for patients hospitalized with COVID-19. A meta-analysis of 10 clinical trials and 9 observational studies in patients hospitalized with COVID-19 shows that receiving oral or intravenous vitamin C daily reduces the odds of in-hospital mortality by 41% when compared with control. When only clinical trials were considered, the odds of in-hospital mortality were decreased by 56%; however, this reduction was only identified in studies using vitamin C 10 grams daily or less. Conversely, supplementation with vitamin C increased the length of intensive care unit (ICU) stay by nearly 2 days and did not impact length of hospital stay or reduce the need for mechanical ventilation, liver injury, or cardiac injury (109955). Similarly, a meta-analysis of 8 clinical studies in primarily hospitalized patients with moderate to severe COVID-19 shows that vitamin C administered orally or intravenously decreases the risk of all-cause mortality by 16% when compared with control (114488). Additionally, a small study found a small improvement in survival when compared with standard care; however, the overall survival rate in this study was low (108075). Another clinical study in patients hospitalized in Turkey with COVID-19 shows that adding high-dose intravenous sodium ascorbate 50 mg/kg to a treatment regimen of hydroxychloroquine, azithromycin, and zinc may improve recovery time, with 57% and 39% of patients achieving total recovery at day 15 in the vitamin C and control groups, respectively (108071). However, the validity of this trial is limited due to unclear reporting. Vitamin C has also been evaluated in combination with other ingredients in patients with long COVID. Preliminary clinical research in adults with long COVID and persistent fatigue shows that taking a specific combination product containing vitamin C 500 mg and L-arginine 1.66 grams (Bioarginina C, Farmacetici Damor) for 28 days increases 6-minute walk test distance by 10% and reduces self-reported fatigue when compared with placebo (110390). However, it is unclear whether these effects are due to vitamin C, L-arginine, or the combination.
• Sepsis. Intravenous vitamin C, alone or in combination with thiamine and/or hydrocortisone, does not prevent organ failure, reduce intensive care or hospital length of stay, or reduce mortality in sepsis or septic shock. Details: Observational research suggests that patients with septic shock are more likely to have low plasma levels of vitamin C (100317). However, three randomized clinical trials in patients with sepsis or septic shock show no benefit with intravenous vitamin C, with or without thiamine, for improving organ function and preventing organ failure when compared with control treatment (102130,104027,114489). A small clinical study in patients with septic shock shows that intravenous vitamin C 50 or 150 mg/kg daily for 4 days does not improve organ dysfunction or failure rates, duration of hospital or intensive care unit (ICU) length of stay, duration of mechanical ventilation, or mortality rate when compared with placebo (114489). Another clinical study in patients with septic shock shows that administering an intravenous bolus of vitamin C 1000 mg followed by a continuous infusion of 250 mg/hour for 96 hours, starting within 24 hours of vasopressor initiation, does not improve 28-day or ICU mortality when compared with placebo. A subgroup analysis shows that the addition of corticosteroids does not affect outcomes in either group (108078). This study may have been inadequately powered to detect a difference between groups. Also, a larger clinical trial in adults with sepsis receiving vasopressor therapy in the ICU shows that intravenous administration of vitamin C 50 mg/kg every 6 hours for up to 4 days increases the risk of death or persistent organ dysfunction at day 28 by 14% to 21% when compared with placebo. There were no differences in mortality at 6 months (109459,111643). Vitamin C has also been frequently studied in patients with sepsis and septic shock in a specific combination regimen (HAT therapy) which includes intravenous vitamin C 1.5-2 grams with hydrocortisone 50 mg every 6 hours and thiamine 200 mg every 12 hours. While some retrospective research has found HAT therapy to be beneficial in sepsis (100315,102980), high quality, prospective clinical research has not confirmed these findings (105447,106620,109956). Several meta-analyses of randomized controlled trials and small clinical studies in patients with sepsis or septic shock show that intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, does not reduce short- or long-term mortality, ICU or hospital length of stay, kidney injury, or duration of mechanical ventilation, but modestly improves duration of vasopressor use and procalcitonin clearance, when compared with placebo or standard care. These analyses also show mixed results with respect to improvement in sequential organ failure assessment (SOFA) scores within 72 hours (105447,106620,106935,108073,109460,111298,111300,111301,111642,112479). Most studies included in the analyses administered HAT therapy for 2-10 days and compared it with normal saline control or with hydrocortisone alone (102129,102998,104027,104028,104032,105446). Although some subgroup analyses suggests that intravenous vitamin C alone in patients with sepsis may improve short-term mortality (106620,111298), other meta-analyses have not shown this benefit in subgroup analyses (111300). In addition, meta-analyses have identified significant publication bias (111298,111300). Long-term follow up from a study in patients with sepsis-induced respiratory and/or cardiovascular dysfunction shows that receiving HAT therapy does not improve cognitive, psychological, or functional status after 6 months and, for some domains, HAT therapy was worse when compared with placebo (111299). Studies evaluating intravenous vitamin C, either alone, as a component of HAT therapy, or in combination with thiamine, in mixed critically ill populations have also shown mixed findings. Four meta-analyses of randomized controlled trials and observational studies show that intravenous vitamin C does not have a significant effect on the length of hospital stay, mortality at 1 month, ICU mortality, use of invasive ventilation, use of renal replacement therapy, organ function, or incidence of kidney injury when compared with placebo or standard care. The meta-analyses reach conflicting conclusions on whether intravenous vitamin C reduces the risk of in-hospital mortality, 30-day mortality, and the duration of ICU stay. When only data from low risk-of-bias clinical trials are considered, the effects of intravenous vitamin C on mortality at any point are no longer significant (106933,106934,109957,113663). However, a subgroup analysis in one of these analyses suggests that intravenous vitamin C as monotherapy, or in doses of at least 10 grams daily, may improve overall mortality (106934). Vitamin C also does not appear to benefit complications from sepsis, such as vasoplegic shock. A small clinical study in adults in the ICU with vasoplegic shock mostly secondary to sepsis and requiring moderate vasopressor support shows that administering intravenous vitamin C as sodium ascorbate 1.5 grams every 6 hours for 5 days or until cessation of vasoactive therapy does not reduce the duration of vasopressors, vasopressor dose, hospital or ICU length of stay, or mortality outcomes when compared with placebo (112475).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Atrophic acne scars. It is unclear if applying topical vitamin C after microblading improves atrophic acne scars. Details: A clinical study in adults with mild to severe atrophic acne scarring shows that applying a serum containing vitamin C 17% to the face after a once-monthly home microblade treatment for 4 months improves the appearance of acne scars at month 5 when compared with baseline (108086). Although this study enrolled a control group that used topical insulin in place of vitamin C, no between-group statistical comparisons were conducted, limiting the validity of this study.
• Age-related macular degeneration (AMD). It is unclear if dietary vitamin C or oral vitamin C taken in combination with other ingredients prevents AMD. Details: An umbrella review of meta-analyses shows that increased dietary intake of vitamin C is associated with 21% higher odds of developing AMD (112095). A population study suggests that vitamin C intake is associated with increased odds of developing age-related maculopathy (9823). However, other population studies have found no association between dietary or supplemental vitamin C intake and the risk of developing AMD (14007,14257). When taken in combination with other ingredients, most clinical and population research shows that taking vitamin C 500 mg along with other antioxidants such as vitamin E 400 IU, beta-carotene 15 mg, and/or elemental zinc 80 mg reduces the risk of visual acuity loss by 23% to 27%, progression to advanced AMD at 5 years by 25% to 32%, and AMD overall (7303,7304,11326,14257,90069). The antioxidant plus zinc combination seems to reduce the risk of progression to advanced AMD in these patients more than taking the antioxidants without zinc (7303,90069). More evidence is needed to determine what role, if any, vitamin C intake has on the risk of developing AMD.
• Aging skin. Topical vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in females aged 30-65 years shows that applying a specific liquid (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% to the face nightly for 8 weeks, in addition to regular facial skin products, improves skin color, elasticity, radiance, smoothness, and appearance of wrinkles when compared with regular facial skin products alone (102355).
• Albuminuria. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study shows that taking vitamin C 1250 mg plus vitamin E 680 IU daily for 4 weeks can reduce the excretion of albumin by about 19% when compared with placebo in patients with type 2 diabetes (10434).
• Allergic rhinitis (hay fever). It is unclear if oral vitamin C is beneficial in patients with hay fever. Details: Epidemiological research has found that higher vitamin C plasma levels are not associated with a decreased risk of allergic rhinitis (15200). However, clinical research shows that some forms of vitamin C might help. In one small clinical study, intranasal vitamin C administered three times daily for 2 weeks reduces nasal secretions, nasal blockage, and edema in up to 74% of patients with perennial allergic rhinitis (15201). Another small clinical study in patients with seasonal allergic rhinitis shows that taking a single oral dose of vitamin C 2 grams reduces bronchial responsiveness to histamine at one hour after ingestion (15202). However, in another small study in patients with seasonal allergic rhinitis taking vitamin C orally in doses up to 4 grams daily for 3 days does not appear to suppress cutaneous or nasal response to histamine when compared to placebo (15203).
• Alzheimer disease. It is unclear if dietary vitamin C helps to prevent this condition. Details: Most epidemiological research has found that dietary intake of vitamin C is associated with a 17% reduced risk of developing Alzheimer disease (4636,9824,10131,13165,90082).
• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral vitamin C helps to prevent ALS. Details: Observational research has found that increased dietary or supplemental intake of vitamin C is not associated with risk of developing ALS (90412).
• Anthracycline cardiotoxicity. Although there is interest in using oral vitamin C for anthracycline-induced cardiac toxicity, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Aspirin-associated gastric damage. It is unclear if oral vitamin C helps to prevent gastric damage caused by aspirin. Details: Some clinical research shows that vitamin C 480 mg might prevent gastric damage associated with taking aspirin 400 mg by decreasing blood loss and preventing decreased gastric blood flow (10357). However, a small clinical study in healthy patients shows that taking vitamin C 500 mg as ascorbic acid with aspirin 600 mg actually increases gastrointestinal permeability to a greater extent than either ingredient taken alone (98781).
• Athletic performance. It is unclear if oral vitamin C improves athletic performance. Details: Although some small preliminary clinical studies suggest that vitamin C might improve certain biomarkers during exercise (82922), a meta-analysis of small clinical trials in older and younger adults shows that taking vitamin C 500-1000 mg daily, with or without vitamin E, does not improve endurance, lean mass, or muscle strength when compared with placebo (102973). A more recent, small clinical study in recreationally trained males shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg daily for 10 weeks while participating in a resistance training program does not improve measures of muscle strength when compared with placebo (109959).
• Atopic disease. It is unclear if dietary vitamin C helps to prevent atopic disease. Details: Population research has found that higher intake of vitamin C is not associated with a reduced risk of eczema, wheeze, IgE-mediated food allergy, or allergic sensitization (90098).
• Attention deficit-hyperactivity disorder (ADHD). Small clinical studies suggest that high-dose oral vitamin C may not improve symptoms in patients with ADHD. Details: Some research suggests that taking megadose vitamins, including vitamin C, does not improve ADHD symptoms (9957,9958,9959). However, other preliminary clinical research shows that taking 25 mg of vitamin C in combination with flaxseed oil providing alpha-linolenic acid 200 mg twice daily might improve measures of attention, impulsivity, restlessness, and self-control in children with ADHD when compared with baseline (14443). It is not clear if these effects are due to vitamin C, flaxseed oil, or the combination.
• Autism spectrum disorder. It is unclear if oral vitamin C is beneficial in patients with autism spectrum disorder. Details: One small clinical study shows that taking vitamin C 8 grams per 70 kg daily for 10 weeks modestly reduces autism symptom severity in school children when compared with placebo (83604).
• Bleeding. It is unclear if intravenous vitamin C can reduce bleeding after total abdominal hysterectomy. Details: A small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery reduces postoperative hemorrhage volume by around 40 mL when compared with placebo (109465).
• Brain tumor. It is unclear if oral vitamin C helps to prevent brain tumors. Details: Population research has found that vitamin C intake is associated with a 14% reduced risk of glioma. This risk reduction was more prevalent in America compared to other geographic locations (98782).
• Breast cancer. It is unclear if oral vitamin C helps to prevent breast cancer, its recurrence, or breast cancer-related mortality. Details: Some epidemiological research has found that dietary vitamin C is associated with a reduced risk of breast cancer (1444,10823,10824). However, other epidemiological research has found no association with dietary or supplemental vitamin C (10825,10826,108080). One cohort study found no association between breast cancer risk and total, dietary, or supplemental vitamin C, regardless of dose, treatment duration, or formulation (single ingredient or combination product). Additionally, hormone and menopausal status did not appear to impact risk. Vitamin C intake might be associated with a reduced risk in individuals with a family history of breast cancer in first-degree relatives (108080). In patients with breast cancer, supplemental or dietary intake of vitamin C might be associated with a reduced risk of mortality. A meta-analysis of results from population research shows that vitamin C supplementation following breast cancer diagnosis is associated with a 15% lower risk of breast cancer-related mortality when compared with no supplementation (90416). A large, observational study in patients with breast cancer undergoing radiation therapy has found that vitamin C supplementation does not reduce the risk of breast cancer recurrence over a period of 5 years when compared with no supplementation. Although the vitamin C group had notably less aggressive tumor types, recurrence-free survival was similar in both vitamin C and control groups (108082). The validity of these findings is limited due to unknown doses of vitamin C and the inclusion of various breast cancer subtypes.
• Burns. Small studies suggest that intravenous vitamin C may modestly improve symptoms in patients with severe burns. Details: A small clinical study in patients with severe burns shows that administering vitamin C intravenously (IV) 66 mg/kg hourly over 24 hours, as part of fluid resuscitation using lactated ringer solution, reduces wound edema and the volume of fluid needed when compared with fluid resuscitation alone (83145). A retrospective review of adults hospitalized with severe burns has found that those who receive a continuous IV infusion of at least 10 grams of vitamin C within 2 days of admission have an in-hospital mortality rate of 46%, compared with 58% for those who do not receive vitamin C (102128).
• Cancer. It is unclear if oral or intravenous vitamin C helps to prevent cancer or cancer-related mortality. Details: Some population research has found that DIETARY intake of vitamin C is linked with a lower risk of cancer and cancer-related mortality (3910,5878,10819,109779). However, clinical research shows that taking vitamin C SUPPLEMENTS does not reduce the risk for cancer (10819,14109,34580,90097). In people with cancer, although some clinical research has shown that taking high-dose vitamin C supplements can improve survival rates (9809,96704), other clinical research has not shown this benefit (4842,4843). In 2003, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that some scientific evidence suggests that antioxidant vitamins, such as vitamin C, may reduce the risk of certain forms of cancer. However, the FDA has determined that there is little scientific evidence supporting this claim (102334). Preliminary clinical research has also evaluated vitamin C supplements in patients with cancer. High-dose oral vitamin C, 10 grams daily, in patients with advanced cancer does not seem to improve survival or decrease disease progression (4842,4843,106617). However, preliminary clinical research suggests high doses of vitamin C, given intravenously, might have a beneficial effect on some outcomes, including survival rate in some patients with cancer (9809,96704,106617). However, there is no benefit to other patients studied in the case reports and this has not been tested in well-designed clinical trials (9809,96704).
• Cardiac arrest. It is unclear if intravenous vitamin C is beneficial for patients after cardiac arrest. Details: A small clinical study conducted in Slovenia in adult survivors of out-of-hospital cardiac arrest shows that administering intravenous vitamin C 1.5 grams every 12 hours for 8 consecutive doses, with the first dose administered within 6 hours of resuscitation, in addition to standard care protects against arrhythmias and reduces the length of intensive care unit (ICU) stay when compared with placebo and standard care. However, intravenous vitamin C does not appear to protect against neurological or myocardial injury, reduce the need for mechanical ventilation, reduce the duration of hospital stay, or increase survival when compared with placebo (113667).
• Carpal tunnel syndrome. Vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamins C, E, B1, B2, B6, and B12, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, and turmeric twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with control (111702). The validity of these effects is limited by a lack of blinding. The study may also be inadequately powered to detect a difference between groups. Additionally, it is unclear if the effects are due to vitamin C, other ingredients, or the combination.
• Cervical cancer. It is unclear if oral vitamin C helps to prevent cervical cancer. Details: Observational research has found that higher vitamin C intake is associated with a 33% to 42% reduced odds of cervical neoplasm. Increasing vitamin C intake by 50 mg daily is associated with an 8% reduced odds of cervical neoplasm (34609,98771).
• Child growth. Some clinical research in pregnant smokers suggests that taking vitamin C during pregnancy may improve pulmonary function in the offspring from birth to 6 years of age. Details: A meta-analysis of 4 data sets from one large clinical study in pregnant adults who smoke at least one cigarette daily shows that taking supplemental vitamin C 500 mg daily during pregnancy reduces lower airway resistance and improves lung capacity of the offspring at 0, 3, 12, and 60 months of age, but does not improve airway obstruction, when compared with control (113670). Additionally, one of the clinical studies included the meta-analysis shows that taking vitamin C during pregnancy lowers the occurrence of wheezing in offspring at 4-6 years of age (114496,114497).
• Chronic fatigue syndrome (CFS). Although there is interest in using oral vitamin C for CFS, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Colistin-induced nephrotoxicity. It is unclear if intravenous vitamin C helps to prevent nephrotoxicity from colistin. Details: A small clinical study shows that intravenous administration of vitamin C 2 grams every 12 hours along with colistin for around 9-10 days does not prevent nephrotoxicity when compared with colistin therapy alone (99839). However, this study was limited by a lack of statistical power to detect differences between the study groups.
• Contrast induced nephropathy. It is unclear if oral vitamin C helps to prevent contrast-induced nephropathy (CIN). Details: Some clinical research shows that taking vitamin C before and after coronary angiography reduces the risk of developing CIN by 33% to 55% when compared with placebo in patients with renal dysfunction (12234,90421). However, other clinical evidence published since 2012 suggests that vitamin C given orally and/or intravenously before and after angiography does not reduce the risk of CIN compared with control in high-risk patients with chronic renal insufficiency or diabetes (91232,91236,90410,90425). Reasons for the discrepancies are not entirely clear. However, it is possible that the lack of significant benefit from vitamin C in the latter studies results from the fact that incidences of CIN have become less common than in the past due to avoidance of dehydration, use of smaller catheters, and use of contrast agents with reduced nephrotoxicity (90429).
• Coronary artery bypass graft (CABG) surgery. It is unclear if intravenous vitamin C helps to improve patient outcomes after CABG surgery. Details: A small clinical study shows that giving vitamin C 5 grams intravenously (IV) before anesthesia induction and 5 grams in the cardioplegia solution used during surgery shortens the length of stay in the intensive care unit (ICU) by about 8 hours (102127). However, some limited research suggests that IV vitamin C does not resolve cardiac surgery complications. A small clinical study in patients with vasoplegia after receiving CABG and other cardiac surgeries shows that receiving IV vitamin C 1.5 grams every 6 hours after being admitted to the ICU does not improve vasoplegia when compared with control (102981).
• Delirium. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Observational research in adults with septic shock has found that receiving intravenous thiamine 400 mg daily with vitamin C 6 grams daily, both in divided doses, is not associated with reduced delirium when compared with control (103001).
• Dental plaque. It is unclear if vitamin C in a chewing gum helps to reduce dental plaque formation. Details: A small clinical study in patients with calculus shows that chewing 10 pieces of gum, each containing 60 mg of vitamin C, daily for 3 months reduces the formation of dental calculus, visible plaque, and the number of bleeding sites when compared not chewing gum (83303). The validity of this finding is limited by a lack of placebo group.
• Depression. It is unclear if oral vitamin C is beneficial for the treatment or prevention of depression. Details: A small clinical study in children and adolescents shows that taking vitamin C 500 mg orally twice daily in combination with fluoxetine 10-20 mg daily for 6 months reduces most symptoms of major depressive disorder when compared with taking fluoxetine alone (90404). However, a small clinical study in adults shows that taking vitamin C up to 1000 mg daily for 2 months does not improve the response rate or decrease symptoms of depression in adults also taking citalopram when compared with citalopram alone (96708). Reasons for these conflicting results may relate to the age of the patients, study duration, or differences in antidepressant medication being taken. One clinical guideline also provisionally recommends against the use of oral vitamin C to treat patients with depression based on low-quality evidence (110318). Some research has also evaluated vitamin C intake for the prevention of depression. A secondary analysis of pre- and peri-menopausal adults enrolled in the Study of Women's Health Across the Nation (SWAN) program suggests that vitamin C intake is inversely associated with depressive symptoms. This association persisted regardless of age, race, physical activity, body mass index, antidepressant use or menopausal status (108083). The validity of these findings is limited due to the secondary nature of this study; additionally, follow-up time is unclear.
• Diabetes. It is unclear if oral vitamin C prevents diabetes. Some low-quality research suggests that vitamin C might improve glycemic control in patients with diabetes. Details: Population research has not found a link between dietary vitamin C and the risk of developing type 2 diabetes (14004). However, low certainty clinical research has found some benefit of taking vitamin C supplements for glycemic control. Two meta-analyses of several small, heterogeneous clinical studies in patients with type 2 diabetes show that taking vitamin C 200-3000 mg daily for 2-48 weeks reduces fasting blood glucose by approximately 11 mg/dL (112478) and glycated hemoglobin (HbA1c) by an average of 0.5% when compared with placebo, standard treatment, or no treatment (105461,112478). Subgroup analyses suggest that durations of supplementation longer than 12 weeks show greater glycemic benefit, and although one meta-analysis suggests there is no dose-response relationship (105461), another meta-analysis suggests that doses of vitamin C 1000 mg and higher are most beneficial for improving glycemic indices (112478). Some research has evaluated the effects of vitamin C supplementation on the lipid profile in patients with diabetes, with mixed findings. One meta-analysis of 17 small clinical studies shows that taking vitamin C 200-3000 mg daily for 2 to 48 weeks improves levels of triglycerides and total cholesterol, but not low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. Subgroup analysis suggests that study durations of at least 12 weeks show greater benefit (106621). However, two other meta-analyses in patients with diabetes, one of 16 small heterogenous clinical studies and one of 11 small clinical studies, show no clinically important improvement in lipid levels after vitamin C supplementation (105461,105464).
• Dry mouth. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical trial in patients receiving radiotherapy for head and neck cancer shows that taking vitamin E 100 IU and vitamin C 500 mg twice daily for an average of 3 months improves dry mouth when compared to baseline (99080). The validity of these results is limited by the lack of comparison with a control group.
• Endometrial cancer. Increased dietary vitamin C has been linked to reduced risk of endometrial cancer. Details: Population research has found that intake of vitamin C from dietary sources is associated with a slightly decreased risk of endometrial cancer when compared with control. However, this benefit is not observed when results from a prospective cohort study are assessed (34578).
• Endometriosis. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with endometriosis and pelvic pain shows that taking vitamin C 1000 mg and vitamin E 800 IU daily for 8 weeks improves dysmenorrhea, dyspareunia, and chronic pelvic pain scores when compared with placebo. Vitamin C and vitamin E supplementation also reduces some biochemical markers of oxidative stress when compared with placebo (106622). Additionally, a meta-analysis of 4 other, mostly small clinical studies in patients with endometriosis shows that taking vitamin C 1000 mg and vitamin E 800-1200 IU daily for 6-8 weeks reduces chronic pelvic pain and improves dysmenorrhea and dyspareunia when compared with placebo (114491).
• Endoscopy-associated adverse effects. It is unclear if a topical vitamin C spray reduces mucosal irritation in patients undergoing Lugol chromoendoscopy. Details: A small clinical trial in patients receiving a Lugol chromoendoscopy shows that spraying a vitamin C 2% solution after the application of the Lugol iodine 2% solution reduces the severity of mucosal irritation, heartburn, and pain when compared with using a normal saline spray after the Lugol iodine 2% solution (104030).
• Esophageal cancer. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Population research has found that higher dietary intake of vitamin C is associated with reduced odds of esophageal adenocarcinoma. A 50 gram increase in dietary vitamin C intake is associated with a 13% reduced odds of esophageal cancer (34551,98770). However, a meta-analysis of clinical research shows that taking a vitamin C supplement in combination with beta-carotene and vitamin E does not reduce the risk of esophageal cancer (34581).
• Exercise-induced asthma. Small clinical studies suggest that oral vitamin C may modestly improve symptoms in patients with exercise-induced asthma. Details: A meta-analysis of the available clinical research shows that vitamin C supplementation might reduce exercise-induced breathlessness when compared with placebo or control. However, the available research is of poor quality, and no clear conclusions can be drawn regarding its benefits for exercise-induced asthma (90409).
• Exercise-induced muscle damage. It is unclear if oral vitamin C is beneficial in exercise-induced muscle damage. Details: A small clinical study in healthy females shows that taking vitamin C 1000 mg before moderate intensity cycling does not prevent muscle damage when compared with placebo (99837). Another small clinical study in endurance-trained runners shows that taking vitamin C 1000 mg and vitamin E (as alpha-tocopherol) 235 mg 2 hours prior to an exercise protocol does not reduce delayed onset muscle soreness or improve other markers of exercise-induced muscle damage when compared with placebo (109961).
• Gallbladder disease. It is unclear if oral vitamin C reduces the risk of gallbladder disease. Details: Cross-sectional epidemiological evidence has found that vitamin C supplementation and increased vitamin C serum levels are associated with a decreased risk of developing gallbladder disease in females, but not males (5877).
• Gastric cancer. It is unclear if dietary or supplemental vitamin C reduces the risk of gastric cancer. Details: Most population research has not found an association between DIETARY intake of vitamin C and gastric cancer risk (9194,10822,10819,90083). Also, clinical research shows that taking vitamin C supplements in combination with other antioxidants does not reduce the risk of gastric cancer or precancerous gastric lesions (14447,34581,90085). However, some research suggests that it might be associated with a reduced risk for specific forms of gastric cancer (9838,90083). One clinical study shows that taking vitamin C orally 500 mg daily for 6 months after eradication of Helicobacter pylori infection decreases the incidence of precancerous changes in stomach tissue when compared with no treatment (10359). Also, other clinical research shows that taking vitamin C orally 1 gram daily helps promote the regression of precancerous gastric lesions in people at high risk for gastric cancer (2579). In 2009, the US Food and Drug Administration (FDA) determined that it would allow a qualified health claim stating that vitamin C supplements may reduce the risk of gastric cancer. However, the FDA has concluded that it is highly uncertain that vitamin C supplements actually reduce the risk of gastric cancer (102332).
• Gastritis. There is limited evidence on the oral use of vitamin C in omeprazole-induced corpus gastritis. Details: A small clinical study shows that taking vitamin C orally 1200 mg daily along with omeprazole decreases corpus gastritis associated with omeprazole therapy in patients with H. pylori infection (10360).
• Gout. It is unclear if oral vitamin C helps to prevent or manage gout. Details: Population research in men has found that taking vitamin C 500-1500 mg daily from the diet and/or supplements is associated with up to a 34% reduced risk of gout when compared with less than 250 mg daily (16755). Also, men who ingest over 500 mg of vitamin C daily from the diet and supplements have serum uric acid levels that are slightly lower than men who consume less than 90 mg daily (16820). However, taking supplemental vitamin C 500 mg daily for 8 weeks does not seem to lower serum uric acid levels in patients who already have gout (90423).
• Hearing loss. There is limited evidence on the intravenous use of vitamin C in idiopathic sudden sensorineural hearing loss. It is unclear if dietary vitamin C intake can affect the risk of hearing loss. Details: A small clinical study in patients with idiopathic sudden sensorineural hearing loss shows that receiving intravenous high-dose vitamin C 200 mg/kg daily in combination with steroid therapy for 10 days, followed by oral vitamin C 2000 mg daily for 30 days, increases recovery rate two-fold and modestly improves hearing threshold levels when compared with receiving steroid therapy only (90417). In addition, population research in females has found that high dietary intake of vitamin C is associated with a 22% increased risk of developing self-reported hearing loss over a 22-year period when compared with low intake (109807).
• Heart transplant complications. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial shows that a combination of vitamin C 500 mg and vitamin E 400 IU, taken twice daily for 1 year starting within the first 2 years after cardiac transplant, reduced the progression of vasculopathy as measured by intravascular ultrasonography (IVUS) when compared with placebo. This suggests that the combination may help slow the progression of CAV (82826).
• Hepatitis C. It is unclear if oral vitamin C is beneficial in patients with hepatitis C. Details: A small clinical study in patients with confirmed hepatitis C shows that taking vitamin C 1000 mg daily with conventional therapy (sofosbuvir plus daclatasvir) for 4 weeks improves serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), bilirubin, and albumin when compared with conventional therapy alone (109463).
• HIV/AIDS. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small, low-quality study in men with HIV shows that taking vitamin C 250 mg daily in combination with vitamin A, beta-carotene, vitamin E, selenium, and coenzyme Q10 does not improve viral load, although it seems to improve markers of oxidative stress when compared to baseline. However, a 1000 mg dose of vitamin C, as well as higher doses of the other antioxidants, do not seem to provide any additional effect (9830).
• HIV transmission. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A clinical study in HIV-positive mothers shows that taking vitamin B, vitamin C, and vitamin E daily during pregnancy and while breast-feeding for 20 weeks seems to reduce child mortality and HIV transmission through breast milk when compared with taking vitamin A (9801).
• Hyperphosphatemia. Intravenous vitamin C might be beneficial for reducing phosphate levels in patients with end-stage renal disease. Details: A small clinical study in hemodialysis patients with elevated phosphorus levels suggests that administering vitamin C 500 mg intravenously three times weekly for 8 weeks reduces phosphorus levels about seven-fold when compared with placebo (90414).
• Idiopathic interstitial pneumonia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with idiopathic pulmonary fibrosis, a form of idiopathic interstitial pneumonia, shows that taking a combination of vitamin C 250 mg every other day, vitamin D 50,000 IU daily, and vitamin E 200 IU daily for 12 weeks improves some, but not all, measures of lung function and reduces markers of inflammation and oxidative stress when compared to baseline (109464). The validity of these findings is limited by a lack of placebo control group.
• Infertility. It is unclear if oral vitamin C is beneficial in anovulatory females. Details: A very small clinical study suggests that taking vitamin C 400-1000 mg daily might improve fertility, resulting in ovulation and pregnancy in some anovulatory females, when compared to baseline (14018). The validity of these findings is limited by the small study size and lack of a comparator group. However, a very large observational study suggests that there is no association between dietary vitamin C intake and in-vitro fertilization (IVF) outcomes including good oocyte quality, embryo transfer success rates, clinical pregnancy rates, and successful term pregnancy rates in subfertile couples who are candidates for IVF (112097).
• Male infertility. It is unclear if oral or intravenous vitamin C is beneficial in males with infertility. Details: A meta-analysis of three small, low-quality clinical trials in males with infertility shows that taking vitamin C up to 1000 mg daily for up to 12 weeks can improve sperm count, motility, and vitality, but does not seem to increase semen volume or sperm concentration, when compared with control (109461). It is unclear if vitamin C can increase pregnancy rates, as these studies did not assess this outcome. A retrospective study in males with or without varicocele-related infertility has found that taking a specific combination product containing vitamin C 90 mg, zinc 10 mg, L-carnitine fumarate 1725 mg, acetyl-L-carnitine 500 mg, coenzyme Q10 20 mg, folic acid 0.2 mg, selenium 0.05 mg, and vitamin B12 0.015 mg (Proxeed Plus, Sigma-Tau) orally twice daily for 6 months improves sperm count, sperm concentration, and sperm motility when compared with baseline. Improvement in semen parameters were greatest in subjects with more severe varicoceles. The validity of this study is limited by the lack of a comparator group (111296).
• Mastalgia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in patients with mastalgia shows that taking a combination of vitamin C 100 mg, vitamin B12, and gamma-linolenic acid daily for 12 weeks does not improve the proportion of patients with minimal or no pain when compared with placebo (111059).
• Melasma. It is unclear if topical vitamin C is beneficial in patients with melasma. Details: A small clinical study in patients with bilateral symmetrically distributed facial melasma shows that applying 0.5 mL of vitamin C (Cosmotech, Alpha Medical Cosmotech) following dermapen microneedling every 2 weeks for 6 weeks is similarly effective to tranexamic acid for improving melasma severity and pigmented, but not vascular, findings on dermoscopic examination (106939). Additionally, a small clinical study in adults with melasma shows that applying 1 to 2 mL of 20% vitamin C solution following dermapen microneedling every 2 weeks for 8 weeks does not improve the degree of pigmentation when compared with topical metformin but does improve the degree of pigmentation when compared to baseline (115610).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin C is beneficial in patients with NAFLD. Details: A clinical study in patients with NAFLD shows that taking vitamin C 250 mg, 1000 mg, or 2000 mg daily for 12 weeks improves some biochemical markers of liver health and glucose metabolism when compared with baseline. However, the improvement from baseline was similar between groups (106942).
• Nonalcoholic steatohepatitis (NASH). Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research suggests vitamin C in combination with vitamin E might improve hepatic fibrosis in patients with NASH. However, it does not seem to decrease liver inflammation (14005).
• Non-Hodgkin lymphoma. It is unclear if oral vitamin C reduces the risk of developing diffuse large B-cell lymphoma. Details: In one population study, higher dietary or supplemental intake of vitamin C was associated with a reduced risk of diffuse large B-cell lymphoma, a type of non-Hodgkin lymphoma, when compared with lower intake in postmenopausal adults (90945).
• Oral cancer. It is unclear if oral vitamin C reduces the risk of developing oral cancer. Details: Population research has found that higher dietary intake of vitamin C is associated with a reduced risk of oral cancer (10821). However, clinical research has not shown benefit with oral vitamin C supplements. A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Oral leukoplakia. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in Japanese adults with oral leukoplakia shows that taking vitamin C 500 mg and beta-carotene 10 mg daily for 12 months does not improve leukoplakia symptoms or reduce the development of oral cancer over 5 years when compared with vitamin C 50 mg daily (91384).
• Osteoarthritis. It is unclear if dietary vitamin C reduces the risk of developing osteoarthritis. Details: Observational research has found that increased vitamin C from dietary sources is associated with a reduced risk of cartilage loss and disease progression in people with osteoarthritis (5881).
• Osteoporosis. It is unclear if dietary vitamin C improves bone density or reduces fracture risk in patients at risk for osteoporosis. Details: Some cross-sectional observational research in postmenopausal patients without a history of smoking or estrogen use has found that higher serum vitamin C levels are associated with lower bone mineral density (9828). However, other observational research in a larger population of adults at risk for osteoporosis has found that higher dietary vitamin C intake is not associated with fracture risk (104415).
• Ovarian cancer. Dietary vitamin C might not affect the risk of ovarian cancer. Details: Epidemiological research has found that dietary vitamin C intake is not linked with ovarian cancer risk (9193,102977).
• Pancreatitis. It is unclear if intravenous vitamin C is beneficial in patients with acute pancreatitis. Details: A small meta-analysis of clinical studies in patients with acute pancreatitis shows that intravenous vitamin C does not improve the odds of developing organ failure when compared with placebo or no intervention. Intravenous vitamin C seems to reduce hospital stay, but not in-hospital mortality (106941).
• Parkinson disease. Dietary vitamin C might not affect the risk of developing this condition. Details: Observational research has found that moderate or high dietary intake of vitamin C is not associated with a reduced risk of Parkinson disease (83316).
• Periodontitis. Oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. It is also unclear if dietary vitamin C reduces the risk of periodontitis. Details: A small clinical study in patients with moderate or advanced periodontitis shows that taking a supplement containing vitamin C 100 mg, alpha-lipoic acid, coenzyme Q10, cranberry extract, grapeseed extract, selenium, vitamin E, and zinc twice daily for 8 weeks in addition to standard nonsurgical therapy does not improve periodontal indices including bleeding on probing, gingival recession, plaque index, or inflammation, among others, when compared with placebo (111708). It is unclear if these effects are due to vitamin C, other ingredients, or the combination. There is also interest in whether dietary vitamin C intake impacts the risk of periodontitis. Observational research in US adults has found that individuals with dietary intake of vitamin C in the third quartile, but not the second or fourth quartiles, have lower odds of periodontitis when compared with vitamin C intake in the lowest quartile. Furthermore, the investigators identified a non-linear relationship between vitamin C intake and periodontitis risk, suggesting that individuals with intakes either much lower or much higher than 158 mg daily are at increased risk of developing periodontitis (109958).
• Peripheral arterial disease (PAD). It is unclear if dietary vitamin C helps to reduce the risk of developing PAD. Details: In females, epidemiological evidence has found that dietary intake of vitamin C of 142 mg daily or greater is associated with a 36% reduced risk of PAD when compared with lower intake levels of less than 80 mg daily (10130).
• Physical performance. It is unclear if oral vitamin C helps to improve physical performance and muscle strength in older people. Details: Population research has found that higher intake of dietary vitamin C is associated with improved physical performance and muscle strength in elderly people (14006). In contrast, a small clinical study in elderly men undergoing strength training shows that taking vitamin C 1000 mg and vitamin E 258IU daily for 12 weeks does not increase strength, and might even attenuate increases in muscle mass, when compared with strength training alone (96701).
• Pneumonia. It is unclear if oral or intravenous vitamin C helps to prevent or treat pneumonia. Details: A meta-analysis of 6 clinical studies in adults with community-acquired pneumonia shows that oral or intravenous vitamin C does not reduce overall mortality, hospital or intensive care unit length of stay, or the risk of mechanical ventilation when compared with control (114490). The interpretation of these results is limited by significant heterogeneity of the included studies. An earlier meta-analysis of two small, low-quality clinical studies in children shows that vitamin C does not seem to reduce the risk of pneumonia when compared with a control (104033).
• Postoperative recovery. It is unclear if oral or intravenous vitamin C improves postoperative recovery. Details: Meta-analyses of clinical research show that oral or intravenous vitamin C can shorten the duration of hospitalization after cardiac surgery when compared with control (91233,96703). However, other research shows no decrease in intensive care unit (ICU) or hospital stay with vitamin C supplementation (96705), while another clinical study in patients undergoing cardiac surgery with extracorporeal circulation shows that intravenous vitamin C administered during surgery and 48 hours after surgery reduces ICU stay and re-admission rates, wound infection, and hospital mortality, but not length of hospital stay, when compared with control (114492). A meta-analysis of 37 clinical trials in adults undergoing low- to high-risk noncardiac surgery (i.e., orthopedic, abdominal, gynecologic, or kidney transplantation), shows that receiving perioperative vitamin C, either orally or intravenously, does not improve duration of hospitalization or overall mortality when compared with control (108087).
• Postoperative pulmonary complications. It is unclear if intravenous vitamin C improves postoperative pulmonary complications. Details: A large, single-blind clinical study in patients with recent cardiac surgery with extracorporeal circulation shows that parenteral administration of vitamin C 50 mg/kg intraoperatively and 50 mg/kg every 6 hours for the next 48 hours, followed by oral vitamin C 2000 mg daily until 1-week post-discharge, reduces the incidence of postoperative pulmonary complications (PPC) by 22% and improves PPC severity scores when compared with control. Specifically, vitamin C reduces the incidence of pneumothorax, pleural effusion, pneumonia, and re-intubation and may ameliorate lung damage as suggested by higher Horowitz index when compared with control (114492). A small clinical trial in patients undergoing low-risk cardiac surgery shows that receiving intravenous vitamin C 1 gram 10 minutes after anesthesia might slightly reduce the rate of postoperative pulmonary complications when compared with receiving a saline injection (104034).
• Postoperative swelling. It is unclear if vitamin C reduces postoperative swelling after dental surgery. Details: A small observational study in adults undergoing surgery for wisdom tooth extraction shows that taking vitamin C 500 mg three times daily for 7 days in addition to standard treatment reduces swelling 7 days after surgery when compared with control. However, vitamin C does not seem to reduce swelling 3 days after surgery when compared with control, suggesting that longer durations are needed for anti-inflammatory effects (113664).
• Premature rupture of membranes (PROM). Oral vitamin C seems to reduce the risk of PROM in some patients; however, the addition of oral vitamin E seems to negate any benefit. Details: A meta-analysis of clinical research shows that taking vitamin C alone decreases the risk of both term and preterm PROM by 45% and 34%, respectively, when compared with placebo or control (96707). Another meta-analysis of clinical research shows that taking vitamin C during pregnancy decreases the risk of PROM by 43% and preterm PROM by 33%, but does not decrease the risk of term PROM, when compared with a control. While vitamin C was studied in doses of 100, 500, and 1000 mg daily, the decreased risk of PROM was only observed in studies of 100 mg daily (114493). A moderate-sized clinical study in patients with a history of PROM shows that taking vitamin C 100 mg daily, starting at 14 weeks' gestation, increases the gestational age at recurrent PROM by around 1 week and increases the gestational age at birth by around 1.3 weeks when compared with placebo (109960). Additionally, a meta-analysis of observational studies suggests that vitamin C levels in the blood tend to be lower in patients with PROM, particularly preterm PROM (114493). Taking vitamin C in combination with vitamin E, however, does not seem to reduce the risk of term or preterm PROM; some research suggests that it might even increase the risk of non-preterm PROM (83472,96707). However, other research shows that taking vitamin C 1000 mg plus vitamin E 400 IU daily, beginning at 24 to 34 weeks gestation and continuing until delivery, may help increase the latency period until delivery by 5 days and increase gestational age at delivery by almost 1 week when compared with placebo in patients with preterm PROM (90078).
• Pressure ulcers. It is unclear if oral vitamin C, when used alone or in combination with other ingredients, can improve the healing of pressure ulcers. Details: A small clinical study in institutionalized patients with pressure ulcers shows that taking vitamin C 500 mg twice daily for 12 weeks does not improve wound closure or increase healing rates when compared with vitamin C 10 mg twice daily (83617). Oral vitamin C has also been evaluated in combination with other ingredients for the treatment of grade II-IV pressure ulcers. Two small clinical studies in hospitalized patients with pressure ulcers shows that administering an oral nutritional supplement enriched with vitamin C, L-arginine, and zinc improves ulcer healing when compared with a standard diet (31953,87173). Also, clinical research in patients living in long-term care facilities shows that taking an oral nutritional supplement enriched in protein, vitamin C, L-arginine, and zinc daily for 9 weeks reduces ulcer area and decreases oozing when compared to baseline (32045). The validity of this finding is limited by the lack of a comparator group.
• Radiation proctopathy. Oral vitamin C has only been evaluated in combination with vitamin E; its effect when used alone is unclear. Details: A small clinical study in patients with chronic radiation proctitis shows that vitamin C 500 mg plus vitamin E 400 IU three times daily might improve symptoms when compared with baseline (9825). The validity of these findings is limited by the lack of a comparator group.
• Renal cell carcinoma. It is unclear if increased dietary intake of vitamin C helps to reduce the risk of renal cell carcinoma. Details: Population research has found that increased dietary intake of vitamin C is associated with a 12% reduced risk of renal cell carcinoma (98779).
• Respiratory tract infections. It is unclear if oral vitamin C is beneficial for preventing respiratory tract infections or reducing the duration of these infections. Details: A meta-analysis of clinical research in children and adults shows that, when compared with placebo, oral vitamin C supplementation reduces the average number of symptomatic days per individual, but does not reduce the average symptom days per respiratory episode. Also, vitamin C intake does not reduce the incidence or severity of respiratory disease or improve recovery in hospitalized patients with respiratory tract infections (108077). The validity of this trial is limited by the high heterogeneity of included studies, which evaluated various vitamin C regimens, ranging from 100 mg to 8 grams daily, as preventive therapy or as an adjuvant to active treatment. A clinical study in children aged 3-10 years shows that taking vitamin C 50 mg in combination with a specific product (Lab4) containing Lactobacillus acidophilus, Bifidobacterium bifidum, and Bifidobacterium animalis subsp. lactis daily for 6 months reduces the incidence of cough and sore throat by 16% and 20%, respectively, when compared with placebo. However, it did not improve total symptoms, nasal congestion, nasal discharge, or sneezing. Also, aside from a 33% reduction in the average number of days with a sore throat, daily supplementation does not reduce the duration of individual symptoms or total symptoms (106943). It is unclear if these effects are due to vitamin C, the probiotics, or the combination.
• Restless legs syndrome (RLS). It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in hemodialysis patients with RLS shows that taking vitamin C 200 mg daily, alone or in combination with vitamin E 400 mg, for 8 weeks reduces the severity of RLS when compared with placebo (90093). More research is needed to determine if vitamin C is beneficial in treating RLS that is not associated with hemodialysis.
• Sunburn. Topical and oral vitamin C has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Taking vitamin C orally in combination with vitamin E seems to prevent ultraviolet (UV) radiation-induced erythema (sunburn) (4715,4716). Vitamin C in combination with high dose oral RRR-alpha-tocopherol (natural vitamin E) seems to protect against skin inflammation after exposure to UV radiation (4715). Also, applying topical vitamin C in combination with topical vitamin E and melatonin seems to provide modest photoprotective effects when used prior to UV exposure. However, it has no effect when used during or after UV exposure (4713,4714).
• Stress. It is unclear if oral vitamin C helps to reduce symptoms of stress. Details: A small clinical study in healthy adults shows that taking vitamin C 3000 mg daily for 14 days modestly reduces blood pressure and subjective stress response to psychological stress when compared with placebo (10353).
• Stroke. Observational research has found that although taking vitamin C supplements does not seem to be beneficial, eating more vitamin C-rich food is linked with reduced risk of stroke. Details: Lower plasma levels of vitamin C have been associated with increased stroke risk (90408). Additionally, population research has found that higher dietary intake of vitamin C is associated with a 8% to 19% reduction in stroke risk when compared to lower intake (90408,109779). This reduction appears to be dose-dependent, with each 100 mg/day increase in dietary vitamin C intake associated with about a 17% reduction (90408). However, taking vitamin C supplements has not been found to be associated with reduced stroke risk (1449,90408).
• Tetanus. It is unclear if intravenous vitamin C helps to reduce symptoms of tetanus. Details: A low quality clinical trial in children and young adults with tetanus shows that intravenous vitamin C 1 gram daily along with conventional treatment reduces fatality when compared to control (21539).
• Tooth extraction. It is unclear if oral vitamin C is beneficial for reducing pain or improving healing after tooth extraction. Details: A small clinical study in healthy patients aged 14-41 years who are undergoing bilateral premolar extraction shows that taking vitamin C 200 mg three times daily, beginning immediately after extraction and continued for 10 days, improves pain on days 1-3, and may reduce mesio-distal wound size between days 1 and 7, when compared with placebo, but not when compared with vitamin C 500 mg three times daily. A dose of 500 mg three times daily did not improve pain scores or extraction wound healing when compared with placebo (108084). The validity of this trial is limited by the short duration of treatment; additionally, this study did not report baseline vitamin C levels.
• Urinary tract infections (UTIs). Although there is interest in using oral vitamin C for UTIs, there is insufficient reliable information about the clinical effects of vitamin C for this condition.
• Vascular dementia. It is unclear if oral vitamin C reduces the risk of vascular dementia. Details: Population research has found that supplemental intake of vitamin C and vitamin E is associated with a reduced risk of vascular dementia in Japanese-American men (4636). However, when cases in which dementia was diagnosed prior to the study are excluded from data analysis, intake of vitamin C and vitamin E is not associated with a reduced risk of vascular dementia in these patients (9824).
• Wound healing. It is unclear if oral vitamin C improves the healing of chronic foot ulcers. It is also unclear if intravenous vitamin C improves healing of surgical wounds after total abdominal hysterectomy. Details: A very small clinical study in adults with chronic foot ulcers shows that taking slow-release vitamin C 500 mg daily for 8 weeks seems to result in a median of 100% ulcer healing, compared with a median of 14% ulcer healing in patients taking glucosamine 1000 mg daily (105456). This finding is limited due to the small and heterogeneous patient population, which included patients with diabetes, vascular disease, and/or vitamin C deficiency. Another small clinical study in patients undergoing total abdominal hysterectomy shows that administration of intravenous vitamin C 1 gram the night before surgery and 1 gram during surgery does not reduce the rate of surgical site infection or wound dehiscence when compared with placebo (109465). However, this study may not have been adequately powered to detect differences between groups. More evidence is needed to rate vitamin C for these uses.

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POSSIBLY SAFE ...when used orally and appropriately, short-term. Ashwagandha has been used with apparent safety in doses of up to 1250 mg daily for up to 6 months (3710,11301,19271,90649,90652,90653,97292,101816,102682,102683) (102684,102685,102687,103476,105824,109586,109588,109589,109590). ...when used topically. Ashwagandha lotion has been used with apparent safety in concentrations up to 8% for up to 2 months (111538).

PREGNANCY: LIKELY UNSAFE
when used orally. Ashwagandha has abortifacient effects (12).

LACTATION:
Insufficient reliable information available; avoid using.

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POSSIBLY SAFE ...when used orally and appropriately. Glycine has been used safely at doses up to 6 grams daily for 4 weeks (106497) and doses up to 9 grams daily for 3 days (10250,10251,10252,92319). There is insufficient reliable information available about the safety of glycine when used topically.

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about GLYCINE)

POSSIBLY SAFE ...when used orally and appropriately, short-term. Inositol has been used with apparent safety in doses up to 18 grams daily for up to 6 weeks or 6 grams daily for 10 weeks (2184,2185,2187,95089). Myo-inositol 4 grams daily has also been used with apparent safety for 6 months (95085). There is insufficient reliable information available about the safety of inositol when used topically.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately. Inositol 80 mg/kg (maximum 2 grams) has been taken daily for up to 12 weeks in children aged 5-12 years (95092). ...when used enterally or intravenously and appropriately in premature infants for treating acute respiratory distress syndrome for up to 10 days (2191,2192,91546,91551).

CHILDREN: POSSIBLY UNSAFE
when used enterally or intravenously for extended durations in premature infants. A large clinical study in infants born at less than 28 weeks' gestation found that myo-inositol 40 mg/kg, given intravenously and then enterally every 12 hours for up to 10 weeks, was associated with a small increased risk of death (98946). Long-term follow-up until 24 months corrected age confirms that the initial increase in mortality rate in the myo-inositol group remained stable; however, there was no difference in a composite outcome of death or survival with moderate or severe neurodevelopmental impairment, as well as no difference in the risk of retinopathy of prematurity, between those who received myo-inositol or control (108819).

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately, short-term. Myo-inositol has been used with apparent safety in amounts up to 4000 mg daily during pregnancy (91548,95082,104688).

LACTATION:
Insufficient reliable information available; avoid using. Breast milk is rich in endogenous inositol (2138); however, the effects of exogenously administered inositol are not known.

(Read more about INOSITOL)

LIKELY SAFE ...when used orally and appropriately, short-term or as a single dose. Melatonin seems to be safe when used up to 8 mg daily for up to 6 months. Melatonin 10 mg daily has been used safely for up to 2 months (1049,1068,1077,1085,1738,1754,5854,5855,5857,12226), (14283,15005,62850,89502,89503,88285,88289,88293,88294,88295)(88296,88299,89508,89510,89511,96313,96314,96316,96317,96319)(96321,97438,99345,103484,106301,106303,107811,110286,110299). ...when used topically and appropriately (1066,1768,1769,4713,4714,96314).

POSSIBLY SAFE ...when doses of up to 8 mg daily are used orally and appropriately for longer than 6 months, doses of 10 mg daily are used for longer than 2 months, or doses of 50 mg daily are used for up to 5 days (7040,7043,62435,106296,107811). There is some evidence melatonin can be used safely in doses of up to 10 mg daily for up to 2 years in some patients (7040,7043,62435). ...when used intravenously under the supervision of a healthcare professional. A one-time dose of intravenous melatonin combined with a single bolus of intracoronary melatonin has been used with apparent safety in one clinical trial (96324).

CHILDREN: POSSIBLY SAFE
when used orally in low doses, short-term (9980,15034,62792,88282,88283,88286,88288,95748,96318,97434)(97439,97446,106293,110292,113216,113223,113224). Although melatonin has been safely used in clinical research in doses up to 12 mg daily (88283), it is often advised that daily doses of melatonin be limited to 3 mg daily for children and infants 6 months or older and 5 mg daily for adolescents (95746). There is some concern that taking melatonin might adversely affect gonadal development in children (1739,1740,1742,1743). While some evidence suggests that long-term use of melatonin in children may delay puberty, the available research includes only three small, observational studies with incomplete follow-up and poor measures of pubertal timing (95747). Although rare, pediatric overdose with melatonin has resulted in hospitalization, mechanical ventilation, and death (108145). Due to potential risks, melatonin should be used only in children with a medical reason for use; it should not be used to promote sleep in otherwise healthy children. There is insufficient reliable information available about the safety of melatonin when used long-term.

PREGNANCY: POSSIBLY UNSAFE
when used orally or parenterally in high doses or with frequent use. High doses of melatonin 75-300 mg daily seem to inhibit ovulation, causing a contraceptive effect (769,1740,6002,8271,95728). Advise pregnant patients and patients wishing to become pregnant to avoid using melatonin frequently or in high doses. There is insufficient reliable information available about the safety of melatonin in lower doses during pregnancy. Some research shows that taking melatonin 2 mg daily does not affect anterior pituitary hormone levels in females who are not pregnant; this suggests that low doses may not have a contraceptive effect (62898). Other research shows that taking melatonin 3 mg daily during the follicle stimulating stage of in vitro fertilization does not negatively impact pregnancy rates (62818,62819,88297,89512,88297). However, it is not known if melatonin is safe for use throughout pregnancy (95729). Until more is known about the safety of melatonin, avoid using during pregnancy.

LACTATION:
Insufficient reliable information available; avoid using.

(Read more about MELATONIN)

POSSIBLY SAFE ...when used orally and appropriately, short-term. L-theanine has been used safely in clinical research in doses of up to 900 mg daily for 8 weeks (12188,36439,96331,96332,96334,96341,97923,101986,104976). There is insufficient reliable information available about the safety of L-theanine when used long-term.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. A specific L-theanine product (Suntheanine, Taiyo Kagaku) 200 mg twice daily has been used safely in males aged 8-12 years for up to 6 weeks (91744).

PREGNANCY AND LACTATION:
Insufficient reliable information available; avoid using.

(Read more about THEANINE)

LIKELY SAFE ...when used orally, topically, intramuscularly, or intravenously and appropriately. Vitamin C is safe when taken orally in doses below the tolerable upper intake level (UL). Tell patients not to exceed the UL of 2000 mg daily (1959,4713,4714,4844). ...when used intravenously or intramuscularly and appropriately. Injectable vitamin C is an FDA-approved prescription product (15) and has been used with apparent safety in clinical trials up to 150 mg/kg daily for up to 4 days (114489) and up to 200 mg/kg daily for up to 2 days (114492).

POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 2000 mg daily can significantly increase the risk of adverse effects such as osmotic diarrhea and gastrointestinal upset (4844).

CHILDREN: LIKELY SAFE
when used orally and appropriately (4844,10352,14443).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive amounts. Tell patients not to use doses above the tolerable upper intake level (UL) of 400 mg daily for children ages 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years. Higher doses can cause osmotic diarrhea and gastrointestinal upset (4844).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (4844).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses. Tell patients over age 19 not to use doses exceeding the UL of 2000 mg daily when pregnant or breast-feeding and for those 14-18 years of age not to use doses exceeding 1800 mg daily when pregnant or breast-feeding. Higher doses can cause osmotic diarrhea and gastrointestinal upset. Large doses of vitamin C during pregnancy can also cause newborn scurvy (4844); avoid using.

(Read more about VITAMIN C)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking ashwagandha with antidiabetes drugs might increase the risk of hypoglycemia.  Details There is preliminary clinical evidence suggesting that ashwagandha might lower blood glucose levels. Theoretically, ashwagandha might have additive effects when used with antidiabetes drugs and increase the risk of hypoglycemia (19274,90649,102685).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha with antihypertensive drugs might increase the risk of hypotension.  Details Animal research suggests that ashwagandha might lower systolic and diastolic blood pressure (19279). Theoretically, ashwagandha might have additive effects when used with antihypertensive drugs and increase the risk of hypotension.

BENZODIAZEPINES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might increase the sedative effects of benzodiazepines.  Details There is preliminary evidence that ashwagandha might have an additive effect with diazepam (Valium) and clonazepam (Klonopin) (3710). This may also occur with other benzodiazepines.

CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might increase the sedative effects of CNS depressants.  Details Ashwagandha seems to have sedative effects. Theoretically, this may potentiate the effects of barbiturates, other sedatives, and anxiolytics (3710).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, ashwagandha might decrease the levels and clinical effects of CYP1A2 substrates.  Details In vitro research shows that ashwagandha extract induces CYP1A2 enzymes (111404).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, ashwagandha might decrease the levels and clinical effects of CYP3A4 substrates.  Details In vitro research shows that ashwagandha extract induces CYP3A4 enzymes (111404).

HEPATOTOXIC DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha with hepatotoxic drugs might increase the risk of liver damage.  Details Ashwagandha has been linked to cases of acute hepatitis, liver failure, hepatic encephalopathy, autoimmune hepatitis, the need for liver transplantation, and death due to liver failure (102686,107372,110490,110491,111533,111535,112111,113610).

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking ashwagandha might decrease the effects of immunosuppressants.  Details Ashwagandha has demonstrated immunostimulant effects in humans (3710,3711,4114,11301,106786). Animal research has shown that ashwagandha can attenuate the immunosuppression caused by cyclophosphamide (3711,4114).

THYROID HORMONE Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Ashwagandha might increase the effects and adverse effects of thyroid hormone.  Details Concomitant use of ashwagandha with thyroid hormones may cause additive therapeutic and adverse effects. Preliminary clinical research and animal studies suggest that ashwagandha boosts thyroid hormone synthesis and secretion (19281,19282,97292). In one clinical study, ashwagandha increased triiodothyronine (T3) and thyroxine (T4) levels by 41.5% and 19.6%, respectively, and reduced serum TSH levels by 17.4% from baseline in adults with subclinical hypothyroidism (97292).

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CLOZAPINE (Clozaril) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, glycine might decrease the effectiveness of clozapine.  Details One small clinical study in patients with schizophrenia shows that adding glycine to clozapine therapy worsens symptoms of schizophrenia when compared with clozapine alone (10253). The mechanism of this interaction is unclear.

(Read more about GLYCINE)

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = A Theoretically, taking inositol with antidiabetes drugs might increase the risk of hypoglycemia.  Details Clinical research shows that inositol lowers blood glucose levels and glycated hemoglobin (HbA1c) levels in patients with diabetes (95083,95084,95088).

(Read more about INOSITOL)

ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, melatonin may have anticoagulant effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.  Details There are isolated case reports of minor bleeding and decreased prothrombin activity in people taking melatonin with warfarin (Coumadin) (63067). The mechanism, if any, of this interaction is unknown (9181). Taking melatonin orally seems to decrease coagulation activity within one hour of dosing in healthy men (62481).

ANTIDIABETES DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = B Theoretically, taking melatonin with antidiabetes drugs might increase the risk of hypoglycemia.  Details Some clinical research shows that melatonin reduces levels of fasting blood glucose and improves glycemic control (19034,19035,103490). However, other research suggests that melatonin might impair glucose utilization and increase insulin resistance (9713), while other research has found no effect on glucose levels (19036,104368). Until more is known, use melatonin cautiously in combination with antidiabetes drugs.

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = A Theoretically, taking melatonin with antihypertensive drugs might increase the risk of hypotension or hypertension.  Details Some clinical research suggests that taking melatonin decreases blood pressure in healthy adults (1724,62165,62187,63042). Also, melatonin seems to lower systolic and diastolic blood pressure in individuals with high blood pressure at nighttime or untreated essential hypertension (62359,62416,62441,62826). However, melatonin seems to worsen blood pressure in patients who are taking antihypertensive medications. Immediate-release melatonin 5 mg at night in combination with nifedipine GITS (Procardia XL) increases systolic blood pressure an average of 6.5 mmHg, diastolic blood pressure by an average of 4.9 mmHg, and heart rate by 3.9 bpm (6436). Also, results from animal research suggest that melatonin reduces the effectiveness of certain antihypertensive drugs, including methoxamine and clonidine (62432).

CAFFEINE Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Theoretically, taking caffeine with melatonin might increase levels of melatonin.  Details Some evidence suggests that caffeine consumption can decrease endogenous melatonin levels (8265,22303,37585), while other evidence suggests that caffeine increases endogenous melatonin levels (62328). When administered in combination with melatonin supplements, caffeine seems to increase melatonin effects and levels (62352,96315). The reason for this discrepancy is not completely clear. Part of the discrepancy may result from the fact that caffeine can inhibit melatonin synthesis as well as inhibit melatonin metabolism. By functioning as an adenosine receptor antagonist, caffeine may indirectly inhibit the synthesis of melatonin. Conversely, because melatonin and caffeine are both metabolized by cytochrome P450 1A2 (CYP1A2) enzyme, concomitant use of melatonin and caffeine may reduce the metabolism of melatonin, resulting in higher serum levels (22306,96315).

CNS DEPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking melatonin might increase the sedative effects of CNS depressants.  Details Melatonin has sedative effects. Theoretically, concomitant use of melatonin with alcohol, benzodiazepines, or other sedative drugs might cause additive sedation (96315).

CONTRACEPTIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, taking contraceptive drugs with melatonin might increase the effects and adverse effects of melatonin.  Details Contraceptive drugs can increase the levels of endogenous melatonin (8265). Theoretically, these drugs may increase the effects and adverse effects of oral melatonin.

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = D Theoretically, melatonin might increase levels of drugs metabolized by CYP1A2. Also, other CYP1A2 substrates might decrease the metabolism of melatonin, increasing melatonin levels.  Details Melatonin is metabolized in the liver primarily by the CYP2C19 and CYP1A2 enzymes (62118,62405,96315). Theoretically, combined administration of melatonin with drugs metabolized by the CYP1A2 enzyme might reduce the metabolism of these drugs, resulting in increased serum levels. Conversely, some drugs metabolized by CYP1A2 may inhibit the metabolism of melatonin, resulting in increased serum levels of melatonin. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.

CYTOCHROME P450 2C19 (CYP2C19) SUBSTRATES Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = D Theoretically, melatonin might increase levels of drugs metabolized by CYP2C19. Also, other CYP2C19 substrates might decrease the metabolism of melatonin, increasing melatonin levels.  Details Melatonin is metabolized in the liver primarily by the CYP2C19 and CYP1A2 enzymes (62118,62405). Theoretically, combined administration of melatonin with certain drugs metabolized by the CYP2C19 enzyme may reduce the metabolism of these drugs, resulting in increased serum levels. Conversely, some drugs metabolized by CYP2C19 may inhibit the metabolism of melatonin, resulting in increased serum levels of melatonin. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, melatonin might increase levels of drugs metabolized by CYP2D6.  Details Laboratory research suggests that certain lots of melatonin inhibit CYP2D6 (96315). Theoretically, combined administration of melatonin with certain drugs metabolized by the CYP2D6 enzyme may reduce the metabolism of these drugs, resulting in increased serum levels. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, melatonin might increase levels of drugs metabolized by CYP3A4.  Details Laboratory research shows that certain lots of melatonin inhibit CYP3A4 (96315). Theoretically, combined administration of melatonin with certain drugs metabolized by CYP3A4 may reduce the metabolism of these drugs, resulting in increased serum levels. Until more is known, use melatonin cautiously in patients taking drugs metabolized by these enzymes.

FLUMAZENIL (Romazicon) Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking flumazenil with melatonin might reduce the effects of melatonin.  Details Animal research shows that flumazenil may inhibit the effect of melatonin (9703).

FLUVOXAMINE (Luvox) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, taking fluvoxamine with melatonin might increase levels of melatonin.  Details Fluvoxamine can significantly increase melatonin levels. In some cases, fluvoxamine might increase bioavailability of exogenously administered melatonin by up to 20 times (5038,6499,8251). Some researchers think this might be a beneficial interaction and be potentially useful for cases of refractory insomnia (6499). However, this interaction might also cause unwanted excessive drowsiness and possibly other adverse effects. Fluvoxamine is known to increase endogenous melatonin secretion (6498,22313). It seems to increase serum levels of exogenously administered melatonin possibly by decreasing melatonin metabolism by inhibiting cytochrome P450 (CYP450) 1A2 and 2C19 or by inhibiting melatonin elimination. This effect has been found in healthy people taking fluvoxamine 50-75 mg and melatonin 5 mg (5038,6498,6499,8251).

IMMUNOSUPPRESSANTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = B Theoretically, melatonin might interfere with immunosuppressive therapy.  Details Melatonin can stimulate immune function. Theoretically, melatonin might interfere with immunosuppressive therapy (7040).

METHAMPHETAMINE (Desoxyn) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking melatonin with methamphetamine may increase the adverse effects of methamphetamine.  Details Animal research suggests that melatonin exacerbates the adverse effects of methamphetamine, resulting in greater depression of tryptophan hydroxylase (TPH) and tyrosine hydroxylase (TH) activity, as well as a significant reduction in dopamine levels (22307). This has not been shown in humans.

NIFEDIPINE GITS (Procardia XL) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Theoretically, taking melatonin with extended release nifedipine reduces the effects of nifedipine.  Details Melatonin can decrease the effectiveness of extended release nifedipine (GITS). Immediate-release melatonin 5 mg at night in combination with nifedipine GITS 30-60 mg daily increases systolic and blood pressure by an average of 6.5 mmHg and 4.9 mmHg, respectively. Concomitant use with melatonin also increases heart rate by 3.9 bpm (6436). The mechanism of this interaction is not known.

SEIZURE THRESHOLD LOWERING DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking melatonin with drugs that lower the seizure threshold might increase the risk of seizure activity.  Details Some clinical evidence suggests that melatonin may increase the frequency of seizures in certain patients, particularly children with neurological disabilities (8248,9744).

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, melatonin may have antiplatelet effects and may increase the risk of bleeding with warfarin.  Details Three cases of increased prothrombin time have been reported for patients aged 48-72 years who took melatonin orally in combination with warfarin (9181). However, three cases of decreased prothrombin time have also been reported for patients aged 51-84 years who took melatonin orally in combination with warfarin (9181). Until more is known, use melatonin cautiously in patients taking warfarin.

(Read more about MELATONIN)

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theanine might lower blood pressure, potentiating the effects of antihypertensive drugs.  Details Animal research shows that theanine can lower blood pressure in spontaneously hypertensive animals (7687,77354). Theoretically, concomitant use of theanine and antihypertensive drugs might potentiate the antihypertensive activity.

CNS DEPRESSANTS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = D Theoretically, theanine might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.  Details Theoretically, theanine may compete with glutamate and/or increase plasma gamma-aminobutyric acid (GABA) levels, which could cause CNS depression (96334). In one clinical study, some subjects taking oral theanine reported drowsiness (96331).

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ACETAMINOPHEN (Tylenol, others) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Probable •  Level of Evidence = B High-dose vitamin C might slightly prolong the clearance of acetaminophen.  Details A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases (6451). This effect is not likely to be clinically significant.

ALKYLATING AGENTS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

ALUMINUM Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.  Details Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption (10549,10550,10551,21556). In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely (10549). Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

ANTITUMOR ANTIBIOTICS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.  Details The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

ASPIRIN Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase aspirin levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction is not clinically significant.

CHOLINE MAGNESIUM TRISALICYLATE (Trilisate) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046,4531). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

ESTROGENS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C might increase blood levels of estrogens.  Details Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products (129,130,11161). It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall (129,11161). When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements (11161). Monitor these patients for estrogen-related side effects.

FLUPHENAZINE (Prolixin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, vitamin C might decrease levels of fluphenazine.  Details In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started (11017). The mechanism is not known, and there is no further data to confirm this interaction.

INDINAVIR (Crixivan) Interaction Rating = Moderate Be cautious with this combination. Severity = Mild •  Occurrence = Probable •  Level of Evidence = B Vitamin C can modestly reduce indinavir levels.  Details One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown (11300,93578).

LEVOTHYROXINE (Synthroid, others) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Vitamin C can increase levothyroxine absorption.  Details Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH (102978).

NIACIN Interaction Rating = Minor Be watchful with this combination. Severity = Mild •  Occurrence = Possible •  Level of Evidence = A Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.  Details A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

SALSALATE (Disalcid) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acidification of the urine by vitamin C might increase salsalate levels.  Details It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.

WARFARIN (Coumadin) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D High-dose vitamin C might reduce the levels and effectiveness of warfarin.  Details Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption (11566). There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time (9804,9806). Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant (9805,9806,11566,11567). However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR) (90942). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

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General ...Orally, ashwagandha seems to be well-tolerated. Topically, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Diarrhea, gastrointestinal upset, nausea, and vomiting. However, these adverse effects do not commonly occur with typical doses.
Serious Adverse Effects (Rare):
Orally: Some case reports raise concerns about acute hepatitis, acute liver failure, hepatic encephalopathy, the need for liver transplantation, and death due to liver failure with ashwagandha treatment.

Dermatologic ...Orally, dermatitis has been reported in three of 42 patients in a clinical trial (19276).

Endocrine ...A case report describes a 73-year-old female who had taken an ashwagandha root extract (unspecified dose) for 2 years to treat hypothyroidism which had been previously managed with levothyroxine. The patient was diagnosed with hyperthyroidism after presenting with supraventricular tachycardia, chest pain, tremor, dizziness, fatigue, irritability, hair thinning, and low thyroid stimulating hormone (TSH) levels. Hyperthyroidism resolved after discontinuing ashwagandha (108745). Additionally, an otherwise healthy adult who was taking ashwagandha extract orally for 2 months experienced clinical and laboratory-confirmed thyrotoxicosis. Thyrotoxicosis resolved 50 days after discontinuing ashwagandha, without other treatment (114111). Another case report describes a 37-year-old female who presented with moderate symptomatic hyponatremia secondary to adrenal insufficiency after chronic consumption of ashwagandha for 2 years. This subject was effectively managed with oral hydrocortisone (114790).

Gastrointestinal ...Orally, large doses may cause gastrointestinal upset, diarrhea, and vomiting secondary to irritation of the mucous and serous membranes (3710). When taken orally, nausea and abdominal pain (19276,110490,113609) and gastritis and flatulence (90651) have been reported.

Genitourinary ...In one case report, a 28-year-old male with a decrease in libido who was taking ashwagandha 5 grams daily over 10 days subsequently experienced burning, itching, and skin and mucous membrane discoloration of the penis, as well as an oval, dusky, eroded plaque (3 cm) with erythema on the glans penis and prepuce (32537).

Hepatic ...Orally, ashwagandha in doses of 154 mg to 20 grams daily has played a role in several case reports of cholestatic, hepatocellular, and mixed liver injuries. In most of these cases, other causes of liver injury were excluded, and liver failure did not occur. Symptoms included jaundice, pruritus, malaise, fatigue, lethargy, weight loss, nausea, diarrhea, abdominal pain and distension, stool discoloration, and dark urine. Symptom onset was typically 5-180 days from first intake, although in some cases onset occurred after more than 12 months of use (102686,107372,110490,110491,111533,111535,112111,113610,114113). Laboratory findings include elevated aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase, serum bilirubin, and international normalized ratio (INR) (112111,113610,114113). In most cases, liver enzymes normalized within 1-5 months after discontinuation of ashwagandha (102686,107372,110491,111535,112111,114113). However, treatment with corticosteroids, lactulose, ornithine, ursodeoxycholic acid, and plasmapheresis, among other interventions, was required in one case (111533). Rarely, use of oral ashwagandha has been reported to cause hepatic encephalopathy, liver failure requiring liver transplantation, and acute-on-chronic liver failure resulting in death (110490,113610).

Neurologic/CNS ...Orally, ashwagandha has been reported to cause drowsiness (110492,113609). Headache, neck pain, and blurry vision have been reported in a 47-year-old female taking ashwagandha, cannabis, and venlafaxine. Imaging over the course of multiple years and hospital admissions indicated numerous instances of intracranial hemorrhage and multifocal stenosis of intracranial arteries, likely secondary to reversible cerebral vasoconstriction syndrome (RCVS) (112113). It is unclear whether the RCVS and subsequent intracranial hemorrhages were precipitated by ashwagandha, cannabis, or venlafaxine.

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General ...Orally and topically, glycine seems to be well tolerated.

Gastrointestinal ...Soft stools, nausea, vomiting, and upper gastrointestinal (GI) tract discomfort have occurred rarely with oral use of glycine. These symptoms resolve rapidly with discontinuation of glycine (10252,11320,92319). Dry mouth has also been reported but any association to glycine is unclear (92321).

Neurologic/CNS ...Mild sedation has occurred rarely with oral use of glycine. Symptoms resolve rapidly with discontinuation of glycine (10252,11320,92321). Irritability, insomnia, fatigue, memory impairment, headache, and sensory impairment have been reported, but any association with glycine is unclear (92321).

(Read more about GLYCINE)

General ...Orally and intravenously, inositol seems to be well tolerated. Topically, no adverse effects have been reported, although a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Diarrhea, gas, and nausea.

Gastrointestinal ...Orally, inositol may cause nausea, diarrhea, gas, and gastrointestinal discomfort (10387,11972,91547,91549,95089,95090,95092).

Immunologic ...Orally, inositol in combination with omega-3 fatty acids has been associated with reports of cold and allergy symptoms in children in clinical research (95092).

Musculoskeletal ...Orally, inositol in combination with omega-3 fatty acids has been associated with reports of tics and other musculoskeletal side effects in children in clinical research (95092).

Neurologic/CNS ...Orally, inositol may cause dizziness, tiredness, insomnia, agitation, and headache (10387,11972,95089,95092). In combination with omega-3 fatty acids, inositol has been associated with reports of feelings of thirst in children in clinical research (95092).

Psychiatric ...In one case report, a 36-year-old male with adequately controlled bipolar disorder was hospitalized with symptoms of mania after consuming several cans of an energy drink containing inositol, caffeine, taurine, and other ingredients (Red Bull Energy Drink) over a period of 4 days (14302). It is not known if this is related to inositol, caffeine, taurine, a different ingredient, or a combination of the ingredients.

(Read more about INOSITOL)

General ...Orally, melatonin is generally well tolerated.
Most Common Adverse Effects:
Orally: Dizziness, drowsiness, headache, and nausea.
Serious Adverse Effects (Rare):
Orally: There is concern that melatonin may increase the risk for seizure.

Cardiovascular ...Melatonin might increase levels of very low-density lipoprotein (VLDL) cholesterol and triglycerides (62176). Several rare or poorly described cases of abnormal heart rhythms, palpitations, fast heart rate, or chest pain have been reported. However, in these cases, the patients were taking other drugs that could account for the symptoms, and melatonin was not thought to be the cause (1079,9181,62776,62789,63067).

Dermatologic ...Papular skin rash and pruritus has been reported with melatonin use. However, the effect was generally mild and did not require cessation of melatonin treatment (62450,62754,109696), and had similar rates as placebo (96316). Cutaneous flushing has also been reported (62770,62914). Two cases of fixed drug eruption on the genitalia have been reported for patients who used oral melatonin (Nature's Bounty Natural melatonin) for preventing jet lag (88284).

Endocrine ...A case of gynecomastia (increased breast size) has been reported for a 56 year-old patient with amyotrophic lateral sclerosis (ALS) who used oral melatonin, long-term (89430). Also, reduced sperm concentration and sperm motility has been reported for two men who used oral melatonin 3 mg daily for 6 months. Improvement in sperm quality was observed for only one of the two men following melatonin cessation (62231).

Gastrointestinal ...Orally, melatonin may cause nausea (62384,62770), abdominal cramps, or mild abdominal pain (62450,62754,62914,96316), diarrhea (62804,62811,62914), constipation (96316), or decreased appetite (62345,62792). Often these symptoms occur during the first few days of treatment and subside after a few days (62804). In some cases, rates of symptoms are similar between melatonin and placebo (96316). Less often, melatonin has been reported to cause abnormal feces (62450), odd taste in the mouth (1070), or reflux esophagitis (1745) when used orally. A case of exacerbated symptoms of Crohn disease, including increased diarrhea and abdominal cramps, has been reported for a patient who took oral melatonin 3 mg at bedtime for 4 days. Symptoms resolved within 24 hours of melatonin treatment cessation (62218).

Genitourinary ...Orally, melatonin may increase enuresis in adults and children (58685,62450,62710,62770,62804,62804,62811). In perimenopausal adults, melatonin has caused a resumption of spotting or menstrual flow (11806). Decreased libido has been noted for one patient treated with melatonin 3 mg daily for 8 weeks (15216).

Hematologic ...A case of nose bleed has been reported with oral melatonin (62450). Some melatonin preparations contain contaminants that are associated with eosinophilia-myalgia syndrome (9715,9716).

Hepatic ...A case of autoimmune hepatitis has been reported for a patient who took melatonin orally to treat insomnia (63037).

Musculoskeletal ...Preliminary clinical evidence shows that a single dose of melatonin 3 mg may increase fall risk due to increased postural swaying while standing on one or both feet in healthy adults ages 60-71 years (97442). A single case of ataxia has been reported for an 81-year-old female who used melatonin for 4 days (9181). Weakened muscle power has been reported for two patients treated with melatonin 5 mg in the evening (62456). Some melatonin preparations contain contaminants that are associated with eosinophilia-myalgia syndrome (9715,9716).

Neurologic/CNS ...Orally, melatonin may cause migraine-like headache (1070,1077,15034,62384,62450,62710,62754,62804,62792,62914,88288,88293,88294,96318)(106297) or dizziness (62345,62384,62450,62456,62770,62784,62792,62804,62811,89510)(110297). Often these symptoms occur during the first few days of treatment and subside after a few days (62804). Melatonin may also cause drowsiness or fatigue when taken orally (1077,8273,15216,62384,62456,62784,62804,62811,88288,89510,96314,96316,96318,97446)(106293,106297). These symptoms appear to be more common if melatonin is taken in the morning or at very high doses (greater than 50 mg) (8269,62874). A case of excessive drowsiness has been reported when melatonin was combined with citalopram, nortriptyline, and oxycodone. Sedation improved with discontinuation of melatonin (96315). Indiscriminate use of melatonin may cause irregular sleep-wake cycles to occur (62998). Less commonly, melatonin may also cause behavior worsening (62811), confusion or disorientation (63014,63067), nighttime awakening (62710,62811), mood swings or agitation (96318), stereotypy (96318), excitement before bedtime (62811), nightmares or more intense dreams (62401,62462,62780,62784,88283), feelings of a "rocking" sensation (62155), or reduced alertness when taken orally.
A case of generalized epilepsy has reportedly occurred after treatment with melatonin for 4 months (9708). Also, some case reports raise concerns about increased risk of seizure with melatonin treatment, but conflicting evidence suggests that melatonin may decrease the risk of seizures (1699,8248,9695,9697,9744,9746,62123,62256,62384,62754)(63070,63071,89431). One patient experienced hyponatremia with confusion and seizures after taking prolonged-release melatonin 2 mg. However, malnutrition and cannabis abuse were also thought to contribute to this reaction (96321).
Although there is concern that melatonin might affect cognitive function in healthy adults, research in humans suggests that oral or topical melatonin do not impact most measures of cognitive function (97442,97448).

Psychiatric ...Orally, melatonin may cause mood changes, including dysphoria (sadness) (1764), dips in mood (62345,62450,62792), nervousness (62784), or transient depression (1077). Delusions and hallucinations have also been reported in clinical research (62347). An isolated incident of aggressiveness was also noted in a child diagnosed with attention deficit-hyperactivity disorder (ADHD) who took melatonin in combination with methylphenidate (9980). Severe irritability has been reported in two children with autism spectrum disorder who had abruptly discontinued melatonin due to the completion of a clinical trial (106293).

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General ...Orally, L-theanine seems to be well tolerated.
Most Common Adverse Effects:
Orally: Drowsiness, headaches.

Neurologic/CNS ...Orally, L-theanine may cause headaches (36439). Patients have also reported drowsiness, increased duration of sleep, and increased dream activity after oral L-theanine use (96331).
A case of subtle facial tic starting within 4 days of taking L-theanine 400 mg daily has been reported for a pediatric patient. Although the tics reportedly ceased once theanine was discontinued, the child had exhibited tics in the past. Therefore, the adverse effect was not thought to be related to L-theanine (91744).

(Read more about THEANINE)

General ...Orally, intravenously, and topically, vitamin C is well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, esophagitis, heartburn, headache, osmotic diarrhea, nausea, vomiting. Kidney stones have been reported in those prone to kidney stones. Adverse effects are more likely to occur at doses above the tolerable upper intake level of 2 grams daily.
Topically: Irritation and tingling.
Serious Adverse Effects (Rare):
Orally: There have been rare case reports of carotid inner wall thickening after large doses of vitamin C.
Intravenously: There have been case reports of hyperoxalosis and oxalate nephropathy following high-dose infusions of vitamin C.

Cardiovascular ...Evidence from population research has found that high doses of supplemental vitamin C might not be safe for some people. In postmenopausal adults with diabetes, supplemental vitamin C intake in doses greater than 300 mg per day is associated with increased risk of cardiovascular mortality. However, dietary intake of vitamin C is not associated with this risk. Also, vitamin C intake is not associated with an increased risk of cardiovascular mortality in patients without diabetes (12498).
Oral supplementation with vitamin C has also been associated with an increased rate of carotid inner wall thickening in men. There is preliminary evidence that supplemental intake of vitamin C 500 mg daily for 18 months can cause a 2.5-fold increased rate of carotid inner wall thickening in non-smoking men and a 5-fold increased rate in men who smoked. The men in this study were 40-60 years old (1355). This effect was not associated with vitamin C from dietary sources (1355).
There is also some concern that vitamin C may increase the risk of hypertension in some patients. A meta-analysis of clinical research suggests that, in pregnant patients at risk of pre-eclampsia, oral intake of vitamin C along with vitamin E increases the risk of gestational hypertension (83450). Other clinical research shows that oral intake of vitamin C along with grape seed polyphenols can increase both systolic and diastolic blood pressure in hypertensive patients (13162). Three cases of transient hypotension and tachycardia during intravenous administration of vitamin C have also been reported (114490).

Dental ...Orally, vitamin C, particularly chewable tablets, has been associated with dental erosion (83484).

Dermatologic ...Topically, vitamin C might cause tingling or irritation at the site of application (6166). A liquid containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) has been reported to cause mild tingling and skin tightness (102355). It is unclear if these effects are due to vitamin C, the other ingredients, or the combination.

Gastrointestinal ...Orally, the adverse effects of vitamin C are dose-related and include nausea, vomiting, esophagitis, heartburn, abdominal cramps, gastrointestinal obstruction, and diarrhea. Doses greater than the tolerable upper intake level (UL) of 2000 mg per day can increase the risk of adverse effects such as osmotic diarrhea and severe gastrointestinal upset (3042,4844,96707,104450,114493,114490). Mineral forms of vitamin C, such as calcium ascorbate (Ester-C), seem to cause fewer gastrointestinal adverse effects than regular vitamin C (83358). In a case report, high dose intravenous vitamin C was associated with increased thirst (96709).

Genitourinary ...Orally, vitamin C may cause precipitation of urate, oxalate, or cysteine stones or drugs in the urinary tract (10356). Hyperoxaluria, hyperuricosuria, hematuria, and crystalluria have occurred in people taking 1 gram or more per day (3042,90943). Supplemental vitamin C over 250 mg daily has been associated with higher risk for kidney stones in males. There was no clear association found in females, but the analysis might not have been adequately powered to evaluate this outcome (104029). In people with a history of oxalate kidney stones, supplemental vitamin C 1 gram per day appears to increase kidney stone risk by 40% (12653). A case of hematuria, high urine oxalate excretion, and the presence of a ureteral stone has been reported for a 9-year-old male who had taken about 3 grams of vitamin C daily since 3 years of age. The condition resolved with cessation of vitamin C intake (90936).

Hematologic ...Prolonged use of large amounts of vitamin C can result in increased metabolism of vitamin C; subsequent reduction in vitamin C intake may precipitate the development of scurvy (15). In one case, a patient with septic shock and a large intraperitoneal hematoma developed moderate hemolysis and increased methemoglobin 12 hours after a high-dose vitamin C infusion. The patient received a blood transfusion and the hemolysis resolved spontaneously over 48 hours (112479).

Neurologic/CNS ...Orally, the adverse effects of vitamin C are dose-related and include fatigue, headache, insomnia, and sleepiness (3042,4844,83475,83476).

Renal ...Hyperoxalosis and oxalate nephropathy have been reported following high-dose infusions of vitamin C. Hyperoxalosis and acute kidney failure contributed to the death of a 76-year-old patient with metastatic adenocarcinoma of the lung who received 10 courses of intravenous infusions containing vitamins, including vitamin C and other supplements over a period of 1 month. Dosages of vitamin C were not specified but were presumed to be high-dose (106618). In another case, a 34-year-old patient with a history of kidney transplant and cerebral palsy was found unresponsive during outpatient treatment for a respiratory tract infection. The patient was intubated for acute hypoxemic respiratory failure, initiated on vasopressors, hydrocortisone, and antibacterial therapy, and received 16 doses of vitamin C 1.5 grams. Serum creatinine level peaked at greater than 3 times baseline and the patient required hemodialysis for oliguria and uncontrolled acidosis. Kidney biopsy revealed oxalate nephropathy with concomitant drug-induced interstitial nephritis (106625). In another case, a 41-year-old patient with a history of kidney transplant presented with fever, nausea, and decreased urine output 4 days after receiving intravenous vitamin C 7 grams for urothelial carcinoma. Serum creatinine levels increased from 1.7 mg/dL to 7.3 mg/dL over those 4 days, and hemodialysis was initiated 3 days after admission due to anuria. Renal biopsy confirmed the diagnosis of acute oxalate nephropathy (109962).

Other ...Intravenously, hypernatremia and falsely elevated ketone levels is reported in a patient with septic shock and chronic kidney disease after a high-dose vitamin C infusion. The hypernatremia resolved over 24 hours after cessation of the infusion (112479).

(Read more about VITAMIN C)