GabaRest by Brain Research Labs

NatMed Pro Brand Evidence-based Rating (NMBER)

Ingredients hide details

Three capsules contain: Vitamin B6 (as pyridoxine HCl) 50 mg • GABAREST brand Proprietary Blend 1450 mg: GABA (gamma aminobutyric acid), Valerian extract (valeriana officinalis, 0.8% valerenic root acid, microencapsulated), L-Theanine (green tea extract), Passionflower (passiflora incarnata 3.5% aerial extract), Hops extract (humulus lupulus, strobiles). Other Ingredients: White Gelatin Capsule, TriCalcium Phosphate, Magnesium Stearate (veg), Silicon Dioxide.

Brand name products often contain multiple ingredients. To read detailed information about each ingredient, click on the link for the individual ingredient shown above.

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Effectiveness view details

Below is general information about the effectiveness of the known ingredients contained in the product GabaRest. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

GAMMA-AMINOBUTYRIC ACID (GABA) (GABA)

INSUFFICIENT RELIABLE EVIDENCE to RATE

Anxiety. Although there has been interest in using oral GABA for anxiety, there is insufficient reliable information about the clinical effects of GABA for this condition.
Athletic performance. Although there has been interest in using sublingual GABA for athletic performance, there is insufficient reliable information about the clinical effects of GABA for this purpose.
Attention deficit-hyperactivity disorder (ADHD). Although there has been interest in using oral GABA for ADHD, there is insufficient reliable information about the clinical effects of GABA for this condition.
Cerebral palsy. It is unclear if oral GABA is beneficial for cerebral palsy in children. Details: Preliminary clinical research in children with cerebral palsy shows that taking a specific product containing GABA (Gammalon) one to four tablets daily (depending on age) for 2 months, in addition to standard therapy for cerebral palsy, improves mental development, learning, vocabulary, physical function, motor strength and activity, and motor hyperactivity in a greater percentage of children when compared with standard therapy alone (19362). These findings are limited by poor study design.
Chronic bronchitis. It is unclear if oral GABA is beneficial for chronic bronchitis. Details: Preliminary clinical research in adults with chronic bronchitis shows that taking a specific GABA product (Aminalon) 1.5-3 grams daily for 18-20 days, along with conventional treatment for acute exacerbations of bronchitis, increases the duration of subsequent remission by about 3 months when compared with conventional treatment alone (19361).
Cushing syndrome. It is unclear if oral GABA is beneficial for Cushing syndrome. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 1-3 grams daily for one month decreases plasma levels of adrenocorticotropic hormone (ACTH) 60 minutes after administration, as well as cortisol and ACTH levels up to 2 days after GABA discontinuation, when compared with baseline (19363). The validity of these findings is limited by the lack of a comparator group.
Depression. Although there has been interest in using oral GABA for depression, there is insufficient reliable information about the clinical effects of GABA for this condition.
Epilepsy. It is unclear if oral GABA is beneficial for epilepsy. Details: Preliminary clinical research shows that taking a combination of GABA 2.5-3 grams and phosphatidylserine 500 mg daily for 3-8 months reduces seizure frequency when compared with placebo in patients with absence seizures, but not in those with focal aware or focal impaired awareness seizures (19364). Other preliminary clinical research suggests that taking GABA 3 grams with phosphatidylserine 600-1200 mg daily for 2 days does not affect the seizure photosensitivity range in people with photoconvulsive responses (5113).
Hypertension. Preliminary clinical research suggests that oral GABA may modestly reduce blood pressure in patients with mild or borderline hypertension. Details: Preliminary clinical research in adults with hypertension shows that drinking 100 mL of fermented milk containing GABA 10-12 mg daily at breakfast for 12 weeks reduces systolic and diastolic blood pressure by about 17 mmHg and 7 mmHg, respectively, when compared with baseline. Compared with patients treated with a placebo milk, these reductions were significant. However, it is unclear if the placebo milk also differed from the fermented milk in other ways (19367). Other preliminary clinical research in patients with borderline hypertension shows that taking a chlorella supplement containing GABA 20 mg twice daily for 12 weeks reduces systolic blood pressure when compared with placebo (19368). However, these findings are limited by poor study design.
Insomnia. It is unclear if oral GABA is beneficial for insomnia. Details: Two small clinical studies in adults with insomnia show that taking fermented rice germ extract, standardized to provide GABA 75 mg or 300 mg, one hour before bedtime for 4 weeks modestly decreases sleep latency when compared with placebo, but does not improve sleep efficacy or reduce episodes of waking after sleep onset (110134,110135). As these doses were evaluated in separate studies, no direct comparison between GABA 75 mg and 300 mg has been conducted.
Meningitis. It is unclear if oral GABA is beneficial for meningitis. Details: Preliminary clinical research in children aged 7 months to 16 years with meningitis shows that taking a specific GABA product (Aminalon) 0.5-1.5 grams daily, starting within 2-4 weeks of illness and continuing for one month thereafter, decreases the incidence of residual disease manifestations and prevents the development of cerebrospinal syndrome when compared with control (19369). However, this study was conducted prior to the development of current treatment guidelines for meningitis; it is unclear if GABA is beneficial when used in conjunction with current standard care.
Menopausal symptoms. Although there has been interest in using oral GABA for menopausal symptoms, there is insufficient reliable information about the clinical effects of GABA for this purpose.
Motion sickness. It is unclear if oral GABA is beneficial for motion sickness. Details: Preliminary clinical research shows that taking a specific GABA product (Aminalon) 0.5 grams as a single dose 40-50 minutes before induced motion sickness or three times daily for 4 days significantly delays onset of motion sickness when compared with placebo. GABA also decreases the occurrence of motion sickness symptoms including chills, cold sweats, and pallor when compared with placebo (19370).
Obesity. Although there has been interest in using oral and sublingual GABA for weight loss, there is insufficient reliable information about the clinical effects of GABA for this purpose.
Pain (acute). Although there has been interest in using oral and sublingual GABA for acute pain, there is insufficient reliable information about the clinical effects of GABA for this purpose.
Post-traumatic stress disorder (PTSD). Although there has been interest in using oral GABA for PTSD, there is insufficient reliable information about the clinical effects of GABA for this condition.
Prediabetes. It is unclear if oral GABA is beneficial for prediabetes. Details: A small clinical study in adults with prediabetes and overweight or obesity shows that taking GABA 500 mg (GABA, Swanson Health) 3 times daily for 95 days does not improve postprandial glucose response to oral glucose tolerance testing, fasting glucose, glycated hemoglobin (HbA1c), or glycemic variability when compared with placebo (112830).
Premenstrual syndrome (PMS). Although there has been interest in using oral GABA for PMS, there is insufficient reliable information about the clinical effects of GABA for this condition.
Psychological well-being. Although there has been interest in using oral and sublingual GABA to improve well-being, there is insufficient reliable information about the clinical effects of GABA for this purpose.
Stress. It is unclear if oral GABA is beneficial for stress. Details: Preliminary clinical research shows that taking a single dose of GABA 100-200 mg by mouth 10-70 minutes prior to completing a mentally stressful task does not appear to reduce subjective measure of stress when compared with placebo (90568). However, it does attenuate alpha wave reduction and reduces beta wave upsurge on the EEG during testing when compared with placebo (19373,90568). More evidence is needed to rate GABA for these uses.

HOPS

INSUFFICIENT RELIABLE EVIDENCE to RATE

Age-related cognitive decline. It is unclear if oral hops-derived bitter acids are beneficial for memory and attention in patients with age-related cognitive decline. Details: A small exploratory clinical study in older adults aged 45-64 years, with self-awareness of cognitive decline, shows that taking matured hops bitter acids (Kirin Holdings Co. Ltd) 35 mg daily for 12 weeks does not improve memory, attention, or performance on most cognitive tests when compared with placebo (102899). A follow-up clinical study in patients aged 45-69 years with subjective cognitive decline shows that taking the same dose of the same product for 12 weeks also does not improve memory, learning, or selective attention, but might improve divided attention as measured on the Symbol Digit Modalities Test (SDMT), when compared with placebo (105953). Both studies were funded by the supplement manufacturer and conducted in Japan; it is unclear if these findings are generalizable to other geographic locations.
Anxiety. Although there is interest in using oral hops for anxiety, there is insufficient reliable information about the clinical effects of hops for this condition.
Attention deficit-hyperactivity disorder (ADHD). Although there is interest in using oral hops for ADHD, there is insufficient reliable information about the clinical effects of hops for this condition.
Body odor. Although there is interest in using topical hops to reduce body odor, there is insufficient reliable information about the clinical effects of hops for this purpose.
Insomnia. Taking oral hops extract in combination with valerian root extract seems to be modestly beneficial in patients with insomnia. However, the effect of hops extract when used alone is unclear. Details: In patients with diagnosed sleep disorders, taking hops extract in combination with valerian root for at least 28 days seems to be beneficial. One clinical study in adults with mild insomnia shows that taking two tablets of a combination product containing a total of 83.8 mg hops extract and 374 mg valerian root extract nightly seems to modestly improve subjective sleep measures, including sleep latency, when compared with placebo, after 28 days. However, there was no difference in efficacy between treatment groups after only 14 days (15018). Additionally, a small clinical study in patients with non-organic sleep disorders shows that taking a specific fixed combination product (Ze91019) containing hops extract 120 mg and valerian root extract 500 mg daily for 28 days improves sleep latency when compared with placebo (19413). It is unclear if taking hops and valerian root as a single dose is beneficial in healthy patients. One small clinical study in healthy volunteers with poor sleep shows that taking a specific preparation (Dormeasan, Bioforce AG) containing hops extract 460 mg and valerian root extract 460 mg dissolved in 50 mL of honey water once at night increases total sleep time and time spent in deep sleep when compared with placebo (19418). However, another preliminary clinical study in healthy adults shows that taking a single dose of a specific product (Hova, Zyma S.A.) containing hops extract 200 mg and valerian root extract 400 mg does not improve sleep latency when compared with placebo (6248). Research also shows that taking certain combination products containing hops and at least two other ingredients can improve sleep quality. These combination products have combined hops with lemon balm and valerian (Valerina Natt) (19417); or passionflower and valerian (NSF-3, M/s Tablets India) (88193,89406). However, other combination products have not been beneficial. These have combined hops with soya oil, soya lecithin, and cannabis (Cyclamax, Persee Medica) (55382); or with vitamin B6, zizyphus extract, hydrolyzed milk protein (Lactium), and magnesium oxide (LZ Complex3, Sanofi) (95971).
Dyspepsia. Although there is interest in using oral hops-derived bitter acids for dyspepsia, there is insufficient reliable information about the clinical effects of hops for this condition.
Lactation. Although there is interest in using oral hops for increasing lactation, there is insufficient reliable information about the clinical effects of hops for this purpose.
Menopausal symptoms. It is unclear if oral hops extract is beneficial in patients with menopausal symptoms. Details: Small clinical studies in patients with menopausal symptoms show that taking a specific hops extract (MenoHop, Biodynamics) 75.1-300 mg standardized to contain 100-200 mcg of 8-prenylnaringenin daily does not improve menopausal symptoms, including hot flashes, after 8-12 weeks of treatment when compared with placebo (55338,55370).
Obesity. It is unclear if administering bitter hops extract intraduodenally or intragastrically is beneficial in patients with obesity. Details: A very small clinical study in healthy young adult males shows that intraduodenal or intragastric administration of bitter hops extract 100-250 mg once does not affect appetite perception, gastrointestinal symptoms, or subsequent energy intake when compared with control (112233). It is unclear if these results are generalizable to individuals with overweight or obesity.
Overactive bladder. Oral hops extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An observational study in females with overactive bladder suggests that taking a specific combination product (Granu Fink femina, Omega Pharma) containing hops extract 18 mg, sweet sumac bark extract 56 mg, and pumpkin seed oil 227 mg three times daily for 12 weeks decreases the frequency of urination from an average of 0.9 to 0.4 episodes daily and the frequency of leakage when compared with baseline. The study also shows this specific combination product (Granu Fink femina, Omega Pharma) improves quality of life when compared with baseline (103253). The validity of these findings is limited by the lack of a control group. Also, it is unclear if these findings are due to hops extract, other ingredients, or the combination.
Psychological well-being. It is unclear if drinking non-alcoholic beer containing matured hops bitter acids is beneficial in healthy adults. Details: A clinical study in healthy adults shows that consuming 350 mL of non-alcoholic beer containing matured hops bitter acids 35 mg (Kirin Holdings Co. Ltd) daily for 3 weeks improves mood scores on the Profile of Mood States 2 (POMS2) and Two-dimensional Mood Scale (TDMS) when compared with baseline (107813). The validity of these findings is limited by the lack of a control group.
Sexual dysfunction. It is unclear if topical hops gel is beneficial in patients with postmenopausal vaginal atrophy. Details: A small clinical study in adults with postmenopausal vaginal atrophy shows that applying intravaginal topical gel containing hops extract (Barij Essence) daily for 7 days and then twice weekly thereafter for 2 months does not improve sexual desire, sexual arousal, vaginal lubrication, satisfaction, orgasm, sexual pain, or overall measures of sexual dysfunction when compared with intravaginal estradiol (112125). The validity of these effects is limited by baseline differences between groups.
Shift work disorder. It is unclear if drinking non-alcoholic beer containing hops is beneficial in patients with shift work disorder. Details: A small open-label clinical study in healthy female nurses working rotating or night shifts shows that drinking 333 mL of non-alcoholic beer containing hops (San Miguel 0% alcohol) at dinner for 2 weeks reduces sleep latency by about 8 minutes, total activity during the night, andanxiety when compared with baseline. However, it does not appear to increase the duration of sleep (55403). The validity of these findings is limited by the lack of a control group and unconfirmed hops content in the beer.
Vaginal atrophy. Topical hops extract has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An open-label, multicenter clinical study in postmenopausal patients with vaginal atrophy shows that inserting 2.5 grams of a vaginal gel containing hops extract 1%, hyaluronic acid, liposomes, and vitamin E (Gynomunal Vaginal gel or Esvegyne, Polichem SA) into the vagina daily for one week followed by twice weekly for 11 weeks reduces vaginal dryness, burning, itching, and rash when compared with baseline (55339). The validity of these findings is limited by the lack of a control group. Also, it is unclear if these effects are due to hops, other ingredients, or the combination.
Venous leg ulcers. Although there is interest in using topical hops for venous leg ulcers, there is insufficient reliable information about the clinical effects of hops for this condition. More evidence is needed to rate hops for these uses.

(Read more about HOPS)

PASSION FLOWER (Passionflower)

POSSIBLY EFFECTIVE

Anxiety. Oral passion flower has a long history of use as a sedative and may improve symptoms of anxiety in some patients. Details: Preliminary clinical research shows that taking a specific dried alcoholic extract of passion flower (Sedanxio, Tilman SA) 400 mg orally twice daily for 2-8 weeks reduces the severity of non-specific anxiety when compared to baseline (88198). The validity of this finding is limited by the lack of a placebo group. Passionflower has also been evaluated as an adjunct to conventional medication. One clinical small study in patients with generalized anxiety disorder shows that taking a specific passion flower extract (Pasipay, Iran Darouk Pharmaceutical Company) 15 drops three times daily along with sertraline 50-100 mg daily for one month reduces anxiety when compared with taking sertraline alone (95036). Passion flower has also been compared to conventional treatments. One preliminary clinical study shows that taking passion flower extract 90-180 mg daily reduces symptoms of non-specific anxiety when compared to baseline, and seems to be comparable to taking mexazolam (15391). A small clinical study in patients with generalized anxiety disorder shows that taking a specific passion flower extract (Pasipay, Iran Darouk Pharmaceutical Company) 45 drops orally once daily for 28 days reduces anxiety similarly to oxazepam 30 mg daily. However, passion flower appears to have a slower onset of action than oxazepam (8007). This finding is limited because it did not utilize a therapeutic dosing regimen for oxazepam, which is given 3-4 times daily to account for its short half-life. Passion flower has also been studied in combination with other ingredients. A small clinical study in healthy adults shows that taking a combination of herbal extracts containing passion flower 40 mg, valerian root, black horehound, and hawthorn (Euphytose, Bayer HealthCare) 6 times daily with meals for 14 days reduces anxiety and sympathetic and autonomic nervous system activation in response to a psychosocial stressor when compared with placebo (111222). It is unclear if these effects are due to valerian, other ingredients, or the combination.
Insomnia. Moderate-sized clinical studies suggest that oral passion flower may modestly improve total sleep time in patients with insomnia; however, its effects on sleep latency and maintenance are mixed. Details: A moderate-sized clinical study in adults in India with insomnia and stress shows that taking passion flower extract 600 mg daily at bedtime for 30 days increases total sleep time by about 30 minutes and reduces both the time to fall asleep and wake time after sleep onset by about 10 minutes when compared with placebo (114529). The validity of these findings is limited by lack of reporting on baseline use of medications or other substances which may impact sleep and exclusion of patients with severe insomnia. Another moderate-sized clinical study in adults with insomnia shows that taking passion flower extract 60 mg every evening before bedtime for 2 weeks increases total sleep time by around 23 minutes, but doesn't seem to improve sleep efficiency, sleep latency, or awakening after sleep onset, when compared with placebo (102866). Additionally, a smaller clinical study in young adults with mild fluctuations in sleep quality shows that drinking tea prepared by steeping passion flower aerial parts 2 grams in 250 mL of boiling water for 10 minutes every evening, about an hour before bedtime for 7 nights, improves subjective ratings of sleep quality, but not other sleep parameters, when compared with placebo (parsley tea) (17374). Passion flower has also been studied in combination with other ingredients. One small clinical study in adults with primary insomnia shows that taking a specific combination product containing passion flower 80 mg, valerian 300 mg, and hops 30 mg (NSF-3, M/s Tablets India) orally at bedtime for 2 weeks yields similar effects on subjective measures of sleep as zolpidem 10 mg nightly (88193).
Pre-procedural anxiety. Oral passion flower modestly reduces preoperative anxiety. Details: Two small clinical studies in adults awaiting dental surgery or inguinal hernia repair surgery shows that taking a specific passion flower extract (Pasipay, Iran Darouk Pharmaceutical Company) reduces preoperative anxiety when compared with placebo. Passion flower extract was given as 20 drops or 500 mg 90 minutes prior to surgery, with or without another dose on the evening before surgery (88195,88196). Another small clinical study shows that drinking 5 mL of syrup containing passion flower aqueous extract (Passiflora syrup, Sandoz) 700 mg orally 30 minutes before epidural catheter insertion for inguinal hernia repair surgery seems to attenuate anxiety; the placebo group experienced a significant increase in anxiety (88194). This finding is limited because there were no statistical comparisons conducted between groups. Passion flower has also been compared with conventional medications. Three clinical studies show that taking passion flower prior to dental surgery decreases preoperative anxiety similarly to oral midazolam 15 mg. One study used passion flower 260 mg, administered 30 minutes prior to the surgery (95038), the second used 500 mg, administered 60 minutes prior (104206), and the third used 600 mg, administered 45 minutes prior (110014). Of the two studies that evaluated patient preference, patients in one study preferred midazolam, possibly due to its ability to cause perioperative amnesia (95038), whereas there was no preference in the other study (110014). Another clinical study shows that taking passion flower 1000 mg one hour prior to elective minor or moderate surgery reduces preoperative anxiety similarly to melatonin 6 mg; however, passion flower seems to cause more cognitive impairment than melatonin (95037).

INSUFFICIENT RELIABLE EVIDENCE to RATE

Adjustment disorders. Oral passion flower has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One clinical study in patients with adjustment disorder with anxious mood shows that taking two tablets of a specific combination product (Euphytose, Bayer Healthcare) three times daily seems to decrease anxiety symptoms when compared with placebo. One tablet contains the dry extracts of passion flower 40 mg, valerian 40 mg, hawthorn 10 mg, and black horehound 10 mg, as well as the caffeine-containing stimulant herbs kola nut 15 mg and guarana 15 mg (6250). It is unclear if this effect is due to passion flower, other ingredients, or the combination.
Alcohol use disorder. Oral passion flower has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults experiencing alcohol withdrawal symptoms shows that taking one capsule of a combination product (Relief) three times daily for 15 days reduces the frequency of excessive sweating, reduces serum liver enzyme levels, and improves appetite and quality of life when compared to baseline. One capsule contains passion flower extract 30 mg, black seed extract 100 mg, cocoa extract 90 mg, radish extract 165 mg, and saffron extract 15 mg (97280). The validity of these findings is limited by the lack of a comparator group.
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral passion flower is beneficial in patients with ADHD. Details: A small clinical trial in children aged 6-13 years with ADHD shows that taking tablets of passion flower (Pasipay, Iran Darouk Pharmaceutical Company) 0.02 mg/kg orally twice daily for 8 weeks reduces parent and teacher ratings of ADHD symptoms no better than taking methylphenidate (0.5 mg/kg twice daily) (88197).
Benzodiazepine withdrawal. It is unclear if oral passion flower is beneficial for benzodiazepine withdrawal. Details: A moderate-sized observational study in adults with depression or anxiety on antidepressants undergoing a benzodiazepine taper after chronic benzodiazepine use suggests that taking a specific dry extract of passion flower (Tractana, Baldacci) 200-600 mg daily for 3 months is associated with a faster benzodiazepine dose reduction and greater percentage of patients with at least 50% reduction or complete benzodiazepine discontinuation after 1 and 3 months from taper initiation when compared with control (111651). The validity of these effects is limited by a lack of placebo group and the retrospective observational study design.
Congestive heart failure (CHF). Oral passion flower has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in patients with mild CHF shows that taking a combination of passion flower and hawthorn extracts 2 mL three times daily for 6 weeks increases six-minute walking distance when compared with placebo. However, it does not appear to improve exercise capacity on a bicycle ergometer test (19201). It is unclear if this effect is due to passion flower, hawthorn, or the combination. Additionally, hawthorn has been evaluated alone for the management of CHF, with some research suggesting that although it may improve symptoms, it may also be associated with worsened clinical outcomes.
Fibromyalgia. Although there is interest in using oral passion flower for fibromyalgia, there is insufficient reliable information about the clinical effects of passion flower for this condition.
Menopausal symptoms. Although there is interest in using oral passion flower for menopausal symptoms, there is insufficient reliable information about the clinical effects of passion flower for this purpose.
Muscle cramps. Although there is interest in using oral passion flower for muscle cramps, there is insufficient reliable information about the clinical effects of passion flower for this purpose.
Neuropathic pain. Although there is interest in using oral passion flower for neuropathic pain, there is insufficient reliable information about the clinical effects of passion flower for this condition.
Opioid withdrawal. It is unclear if oral passion flower helps to prevent opioid withdrawal. Details: A small preliminary clinical study in adults who are completing an inpatient withdrawal program for opioid addiction shows that taking passion flower liquid extract 60 drops, in combination with clonidine 0.8 mg daily, is better than clonidine alone when used for reducing symptoms such as anxiety, irritability, insomnia, and agitation. However, the combination is no better than clonidine alone for reducing physical symptoms such as tremor and nausea (2303).
Seizures. Although there is interest in using oral passion flower for seizures, there is insufficient reliable information about the clinical effects of passion flower for this condition.
Stress. It is unclear if oral passion flower reduces stress. Details: A moderate-sized clinical study in adults in India with stress and insomnia shows that taking passion flower 600 mg daily at bedtime for 30 days modestly reduces stress when compared with placebo (114529). It is unclear how changes in stressors over the course of the study may have affected results. Additionally, a small clinical study in healthy adults shows that taking a specific combination product (Relaxane, Max Zeller Söhne AG) containing passion flower 90 mg, lemon balm 50 mg, valerian 90 mg, and butterbur 90 mg three times daily for 3 days modestly reduces subjective anxiety scores during social stress testing when compared with placebo or no treatment (97276). It is unclear if this effect is due to passion flower, other ingredients, or the combination. More evidence is needed to rate passion flower for these uses.

(Read more about PASSION FLOWER)

THEANINE (L-Theanine)

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.

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VALERIAN

POSSIBLY EFFECTIVE

Insomnia. Most research shows that taking valerian whole root extract 300-600 mg daily modestly improves subjective sleep quality, although it might take up to 4 weeks to provide benefit. Valerian does not seem to improve sleep latency, sleep duration, or insomnia severity. Details: Although there is a great deal of conflicting research, overall, taking valerian 300-600 mg before bedtime seems to improve sleep quality when compared with placebo. In contrast, no consistent benefit has been seen for sleep latency, sleep duration, or insomnia severity (15046,17577,19406,19409,104010). Older meta-analyses show that valerian root improves sleep quality regardless of its formulation. However, the most recent meta-analysis shows that valerian whole root extract improves sleep quality, while it's unclear whether an unspecified valerian extract is effective (17577,19406,104010). These analyses are limited by significant heterogeneity in valerian dosage and formulation, treatment duration, and included patient populations. Some experts claim that valerian does not work acutely for sleep, and it can take up to 4 weeks for a benefit to be seen (10209,104010). Indeed, most short-term studies assessing valerian as a single dose, or used daily for up to one week, show no benefit for sleep quality when compared with placebo (19407,19408,19411,19414). However, a meta-analysis of studies lasting 4 weeks or longer also did not find a consistent benefit (104010). The benefits of valerian for sleep might vary in different patient populations. A large post-marketing surveillance study in children with restlessness or dyssomnia under the age of 12 has found that taking a specific combination product (Euvegal Forte, Dr. Willmar Schwabe Pharmaceuticals) containing valerian root extract 160 mg and lemon balm extract 80 mg 1-2 tablets once or twice daily is associated with moderate sleep improvement (14416). Also, one clinical study in postmenopausal adults shows that taking valerian root extract 530 mg (Sadamine) twice daily for 28 days moderately improves sleep quality when compared with placebo (19425). Another clinical study in patients undergoing treatment for cancer shows that taking valerian 450 mg 1 hour before bedtime for 8 weeks does not improve objective sleep measures, but might improve subjective sleep ratings and mood, when compared with placebo (19424). Small clinical studies in adults on hemodialysis show that taking valerian 530 mg before bedtime for 1 month improves sleep quality when compared with baseline or placebo. (105718,110712). In one of these studies, improvements in sleep quality were similar when compared with gabapentin (110712). Research also shows that taking specific combination products containing valerian and other ingredients can improve sleep quality. These combination products have combined valerian with hops; lemon balm (Euvegal Forte); lemon balm and hops (Valerina Natt); or passionflower and hops (NSF-3, M/s Tablets India) (10423,15018,19413,19417,19418,19419,88193,89408). Finally, limited research has compared valerian to benzodiazepines. A small clinical study in patients with non-organic insomnia shows that taking valerian extract (LI 156, Sedonium) 600 mg daily for 6 weeks seems to be no different for improving sleep quality when compared with taking low-dose oxazepam 10 mg (19416). Valerian might also improve sleep quality in patients who are resistant to chronic benzodiazepine therapy. In one small study, after tapering the benzodiazepine over two weeks, valerian extract 100 mg three times daily for 15 days improves sleep quality when compared with placebo (8006).

INSUFFICIENT RELIABLE EVIDENCE to RATE

Anxiety. It is unclear if valerian is beneficial for anxiety. Details: Meta-analyses of heterogeneous clinical research show that there is insufficient and contradictory evidence on the use of valerian root for anxiety (104010,110711). However, one analysis suggests that using whole root preparations seems to have greater efficacy than valerian extracts (104010). These meta-analyses are limited by significant heterogeneity in valerian dosage and formulation, treatment duration, and patient populations and concerns related to publication bias (104010,110711). One small clinical study in patients with generalized anxiety disorder (GAD) shows that taking valerian extract containing 81.3 mg valepotriates daily for 4 weeks is no different for reducing anxiety scores when compared with diazepam 6.5 mg or placebo (9896). This study was not adequately powered to detect a difference between groups. Also, a small, quasi-randomized trial in adults with poor sleep quality who are undergoing hemodialysis shows that taking a specific valerian root product (Sedamin, Goldaru Company) 530 mg daily for 1 month improves anxiety scores by 2-3.9 times when compared with placebo. However, not all patients reported anxiety at baseline (105718). In contrast, a small clinical study in healthy adults shows that taking a combination of herbal extracts containing valerian root, passionflower, ballota, and hawthorn (Euphytose) daily for 14 days reduces subjective anxiety and objective sympathetic and autonomic nervous system activation in response to a psychosocial stressor when compared with placebo (111222). It is unclear if these effects are due to valerian, other ingredients, or the combination.
Delirium. Oral valerian has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in adult intensive care unit (ICU) patients with agitation and delirium receiving quetiapine 50-200 mg every 12 hours shows that taking 5 mL of syrup containing valerian root 625 mg and an extract of lemon balm leaf 50 mg every 12 hours improves agitation from baseline similarly to placebo. It is unclear if the improvement from baseline differed between groups (106627).
Depression. It is unclear if valerian is beneficial in patients with depression. Details: A retrospective case series in patients with mild to moderate depression and reports of anxiety has found that taking high-dose valerian 1000 mg with St. John's wort is associated with more rapidly improved depressive symptoms than low-dose valerian 500 mg with St. John's wort (19402). The validity of this study is limited by its retrospective nature and small size. Also, it is unclear if this effect is due to valerian, St. John's wort, or the combination. One small, quasi-randomized trial in adults with poor sleep quality who are undergoing hemodialysis shows that taking a specific valerian root product (Sedamin, Goldaru Company) 530 mg daily for 1 month improves depression scores by 2-3.9 times when compared with placebo. However, not all patients reported depression at baseline (105718).
Dysmenorrhea. One small study suggests that oral valerian may reduce symptoms of dysmenorrhea. Details: A small clinical study shows that taking powdered valerian root 255 mg three times daily for two menstrual cycles reduces pain severity associated with menstruation when compared with placebo (19342).
Menopausal symptoms. Small studies suggest that oral valerian may reduce menopausal symptoms. Details: Two small clinical studies in postmenopausal adults show that taking valerian root (Zardband or Goldaroo Co.) 225 mg three times daily or 530 mg twice daily for 2 months moderately reduces hot flash frequency and severity when compared with placebo (89407,96243). Another small study in adults with menopausal symptoms shows that taking a combination of valerian and fennel extracts 500 mg twice daily for 8 weeks reduces the severity of hot flashes and improves sleep quality but does not reduce the duration or frequency of hot flashes when compared with control (112369). It is unclear if these effects are due to valerian, fennel, or the combination. All 3 studies were conducted in Iran, so it is unclear if these results are generalizable to other geographic locations.
Premenstrual syndrome (PMS). One small study suggests that oral valerian may reduce PMS symptoms. Details: A small clinical study in young adults with PMS shows that taking valerian root extract (Goldaroo Co.) 530 mg twice daily on the last 7 days of the menstrual cycle for 3 cycles moderately reduces the severity of self-reported PMS symptoms when compared with placebo (96239).
Pre-procedural anxiety. One small study suggests that oral valerian may reduce anxiety during wisdom tooth extraction. Details: A small crossover clinical study in patients undergoing impacted mandibular molar extraction shows that taking valerian extract (Dermatologica Ltda.) 100 mg one hour prior to the extraction reduces physiological responses to anxiety to a satisfactory but lesser degree than midazolam 15 mg. Patients expressed no clear preference for either valerian or midazolam for reducing perioperative anxiety (102242). The validity of these findings is limited by the use of subjective outcome measures.
Restless legs syndrome (RLS). It is unclear if oral valerian is beneficial in patients with RLS. Details: A small clinical study in patients with RLS shows that taking valerian (Pharmavite, LLC) 800 mg daily for 8 weeks does not improve RLS symptoms or sleep latency when compared with placebo (19422). However, this study was not adequately powered to detect a difference in RLS symptoms between groups. Conversely, another small clinical study in adults with RLS on hemodialysis shows that taking valerian 530 mg nightly before bed for 1 month reduces symptoms of RLS when compared to baseline; however, valerian's effects were weaker when compared with gabapentin 100 mg nightly (110712). The validity of this study is limited by a lack of a placebo group and a small sample size.
Stress. Two small studies suggest that oral valerian may reduce the stress response in healthy adults who are performing a stressful mental task or a verbal presentation. Details: Two small clinical studies in healthy volunteers shows that taking valerian 100 mg once or 600 mg daily for 7 days prior to participating in a mental stress task or public verbal test reduces physiologic responses to stress and feelings of anxiety when compared to baseline (9893,9895). The validity of these findings is limited by the lack of statistical comparison to the control group. Another small study in healthy volunteers shows that taking a specific combination product containing valerian 360 mg and lemon balm 240 mg (Songha Night, Pharmaton Natural Health Products) reduces anxiety associated with laboratory-induced stress. However increasing the dose to valerian 1080 mg and lemon balm 720 mg seems to increase anxiety (19405).
Tension headache. One small study suggests that oral valerian may reduce tension headache. Details: A small clinical study in patients with frequent tension headaches shows that taking valerian root extract (Sedamin, Goldaru Pharmaceutical Company) 1060 mg daily after dinner for one month modestly reduces headache severity and disability when compared with placebo (103221). More evidence is needed to rate valerian for these uses.

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VITAMIN B6

EFFECTIVE

Pyridoxine-dependent epilepsy. Intravenous vitamin B6 is effective for controlling pyridoxine-dependent seizures. Details: Pyridoxine-dependent seizures are a rare type of refractory seizures in neonates that do not respond to anticonvulsant drugs. These seizures are typically controlled within minutes of intravenous administration of pyridoxine, a form of vitamin B6. Pyridoxine-dependent seizures can be due to genetic (autosomal recessive) pyridoxine dependency, or more commonly, a result of the use of high-dose pyridoxine during pregnancy (8197,8198).
Sideroblastic anemia. Oral vitamin B6 is effective for treating hereditary sideroblastic anemia. Details: Taking vitamin B6 (pyridoxine) orally is effective for treating hereditary sideroblastic anemia (15,9518). Taking the active form of vitamin B6 (pyridoxal-5'-phosphate) also seems to be effective in cases in which the patient does not respond to pyridoxine (93049).
Vitamin B6 deficiency. Oral vitamin B6 is effective for preventing and treating vitamin B6 deficiency. Details: Taking oral vitamin B6 can prevent and treat vitamin B6 deficiency (15).

LIKELY EFFECTIVE

Hyperhomocysteinemia. Taking vitamin B6 orally, alone or in combination with folic acid, is effective for reducing hyperhomocysteinemia. Details: Vitamin B6 (pyridoxine) seems to lower homocysteine concentrations when folic acid and vitamin B12 are at physiologic levels or when given with folic acid and vitamin B12 supplements (9451,83042,107136). A combination of vitamin B6 100 mg and folic acid 0.5 mg daily seems to lower homocysteine levels by about 35% and is recommended for people with postprandial hyperhomocysteinemia (1489,9406). Other research shows that taking pyridoxine 50-200 mg daily reduces postprandial homocysteine levels by 32% to 35% (9406,10350). Pyridoxine also seems to reduce homocysteine levels in patients with kidney failure, kidney transplant patients (1489,6884,9414,9415), or patients who receive general anesthesia with nitrous oxide (9481). However, some research in healthy adults suggests that adding pyridoxine to folic acid might not provide any additional benefit over folic acid alone (9400,9405,9409,50145). Hyperhomocysteinemia is considered by some to be an independent risk factor for atherosclerosis, recurrent thromboembolism, deep vein thrombosis, myocardial infarction, and ischemic stroke (1899,3323,9402,9405,9408,9409). However, elevated homocysteine levels may be a marker, as opposed to a cause, of vascular disease (11387,11388). A 5 µmol/L increase in plasma homocysteine increases the risk of cerebrovascular disease by 50% and the odds of coronary heart disease by 60% and 80% in males and females, respectively (9407,9411). However, it is not clear if reducing homocysteine levels results in reduced cardiovascular morbidity and mortality (1489,6883,6884,9308,9400,9405,9409). Folic acid, vitamin B6, and vitamin B12 supplementation can reduce total homocysteine from 13.4 to 11 µmol/L. However, this reduction does not seem to help with secondary prevention of death or myocardial infarction, and some research even suggests an increase in cardiovascular disease (CVD) risk (11387,13482,50423,83050,97619). There is also debate about whether supplementation with homocysteine-lowering B vitamins can reduce the risk of stroke. A number of large clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with CVD or impaired renal function (11387,13482,50423,83050,96150). However, a more recent meta-analysis shows that B vitamin supplementation modestly reduces the relative risk of stroke by 10% when compared with placebo in patients at risk for or with a history of CVD (97619). Also, a meta-analysis in patients with a history of stroke shows that B vitamin supplementation modestly reduces the relative risk of stroke recurrence by 13% and the risk of vascular death by 11% when compared with placebo (107136).

POSSIBLY EFFECTIVE

Antipsychotic-induced hyperprolactinemia. It is unclear if oral vitamin B6 is beneficial for patients with antipsychotic-induced hyperprolactinemia. Details: Clinical research in male patients with hyperprolactinemia who are on a consistent antipsychotic dose shows that taking vitamin B6 300 mg twice daily for 16 weeks reduces serum prolactin levels by 68%, compared with 37% in patients taking aripiprazole 5 mg twice daily. Also, 67% of patients taking vitamin B6 had prolactin levels less than 40 mcg/mL versus 2% of those taking aripiprazole (107128).
Kidney stones (nephrolithiasis). Oral vitamin B6 seems to decrease urinary oxalate levels and decrease the risk of kidney stone formation in some patients. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally, alone or in combination with magnesium, can decrease urinary oxalate levels in people with type I primary hyperoxaluria, a hereditary disorder (1201,6437,6438,6439,6440,8548,8549,8550). Additionally, a small clinical study in this population suggests that intravenous pyridoxine hydrochloride can reduce urinary oxalate by 25.5% when compared to baseline (90796). In patients with idiopathic hyperoxaluria, taking a combination of pyridoxine 25mg and magnesium oxide 400 mg for 3 months decreases urinary oxalate by approximately 16%, with 68% of patients experiencing a reduction. However, supplementation is less effective than following a low-oxalate diet, which reduces urinary oxalate in 91% of patients by an average of 31% (107127). There is also preliminary evidence that higher pyridoxine intake in females with no history of kidney stones is associated with decreased risk of kidney stone formation (6441), but this association has not been found in males (6442).
Pregnancy-induced nausea and vomiting. Oral vitamin B6 may reduce nausea and vomiting in some pregnant patients and is sometimes used in combination with doxylamine. Details: While some conflicting evidence exists, most small clinical studies suggest that oral vitamin B6 is effective for improving nausea and vomiting associated with pregnancy when compared with baseline or placebo. However, vitamin B6 may not be as effective as ginger (110459). Two small clinical studies show that taking vitamin B6 (pyridoxine) 25 mg every 8 hours for 3-4 days decreases pregnancy-induced nausea severity and vomiting incidence when compared with placebo (6168,16306). A larger clinical trial shows that taking lower doses of vitamin B6, 10 mg every 8 hours over 5 days, improves pregnancy-induced nausea, but not vomiting, when compared with placebo (6167). A small clinical study in patients with mild to moderate nausea and vomiting shows that taking a higher dose of 40 mg twice daily for 4 days is more effective than placebo, but no better than ginger 500 mg twice daily (99404). The American College of Obstetrics and Gynecology (ACOG) considers vitamin B6 at a dose of 10-25 mg 3 to 4 times daily a first-line treatment for pregnancy-induced nausea and vomiting due to its benign safety profile (111601). However, it is not effective for all patients, such as those with hyperemesis gravidarum, a severe form of pregnancy-induced nausea and vomiting. Adding vitamin B6 20 mg three times daily for 2 weeks to intravenous rehydration, metoclopramide, and thiamine seems to be no more effective than placebo for reducing vomiting in hyperemesis gravidarum (99405). Vitamin B6 is also sometimes used in combination with doxylamine. In fact, a combination of vitamin B6 plus doxylamine (Diclegis or Bonjesta, Duchesnay Inc., and various generics) has been approved by the US Food and Drug Administration (FDA) as a prescription product111601). ACOG recommends vitamin B6 in combination with doxylamine as another first-line treatment option (111601). However, the clinical trial used to obtain FDA approval has some methodological problems, and the significance of the results has been questioned. The improvement in symptom scores seen with Diclegis was less than one point on a 13-point scale, which is unlikely to be clinically significant (97998). Also, some clinical research shows that taking pyridoxine 25 mg and doxylamine 12.5 mg is less effective than ondansetron 4 mg when taken every 8 hours for 5 days. Only 41% of the patients using pyridoxine and doxylamine had a clinically significant reduction in nausea, compared to 92% of patients using ondansetron (90797). The combination of vitamin B6 and doxylamine is also studied with acupuncture. A large clinical study in patients with moderate to severe pregnancy-induced nausea and vomiting conducted in China shows that taking vitamin B6-doxylamine (Diclegis, Duchesnay, Inc) 20 to 40 mg each at bedtime for 14 days in combination with daily acupuncture modestly improves patient-reported nausea and vomiting scores when compared with either intervention alone (111820). However, it is unclear whether this improvement is clinically significant.
Premenstrual syndrome (PMS). Oral vitamin B6 seems to reduce PMS symptoms. Details: There is some evidence that taking vitamin B6 (pyridoxine) orally can improve symptoms of PMS such as breast pain or tenderness (mastalgia) and depression in some patients. Pyridoxine in doses of at least 50 mg daily, plus magnesium oxide 200 mg daily, seems to relieve PMS-related anxiety and other symptoms (8555,39007,82962). Although some clinicians advocate doses of pyridoxine 200-500 mg daily for PMS, doses of 50-100 mg daily seem to work just as well. There is no apparent dose-response curve for PMS, so the lowest effective dose should be used. Higher doses might increase the risk of side effects (3093).

POSSIBLY INEFFECTIVE

Age-related cognitive decline. Oral vitamin B6 does not seem to slow age-related cognitive decline. Details: One clinical trial in elderly people with memory complaints shows that taking a combination of B vitamins, including folic acid 0.8 mg, vitamin B12 0.5 mg, and vitamin B6 (form not specified) 20 mg daily for 24 months reduces cerebral atrophy in the gray matter regions associated with Alzheimer disease by up to seven-fold when compared with placebo. However, this protection does not occur in patients with the lowest average blood levels of homocysteine (90374). Furthermore, other clinical research shows that taking vitamin B6 (pyridoxine) 3-75 mg daily in combination with folic acid and vitamin B12 does not improve cognitive function in elderly adults (14392,50225,50510).
Alzheimer disease. Oral vitamin B6 does not seem to improve cognitive function in patients with Alzheimer disease when used in combination with other B vitamins. Also, oral vitamin B6 does not seem to reduce the risk of developing this condition. Details: Clinical research in patients with probable Alzheimer disease taking routine medications shows that taking vitamin B6 25 mg with folic acid 5 mg and vitamin B12 1 mg daily for 18 months does not have a beneficial effect on cognitive function or the severity of disease when compared with placebo. In this study, all patients were consuming a folate-fortified diet (50319). Also, population research in elderly adults has found that a high intake of vitamin B6 from dietary or supplemental sources is not associated with a decreased risk of Alzheimer disease when compared to lower vitamin B6 intake (13165,15270).
Carpal tunnel syndrome. Oral vitamin B6 does not seem to reduce symptoms of carpal tunnel syndrome. Details: Most research shows that people with carpal tunnel syndrome are not generally deficient in vitamin B6 and do not benefit from taking vitamin B6 supplements (8203,8937,9448,9450,9478,9482). Although early studies by a single group of researchers, as well as anecdotal reports, suggest that taking vitamin B6 may relieve carpal tunnel symptoms, more reliable research has not supported these findings (8202,9445,9447,9449,9483,15955,83086). Vitamin B6 has also been evaluated in combination with other ingredients. A moderate-sized clinical study in adults with mild to moderate carpal tunnel syndrome shows that taking a combination product containing vitamin B6, alpha-lipoic acid, acetyl-L-carnitine, phosphatidylserine, turmeric, and vitamins C, E, B1, B2, and B12 twice daily for 60 days reduces symptom severity and pain but does not improve measures of hand and wrist function when compared with a control (111702). The dose of vitamin B6 was not provided. The validity of this study is limited by the lack of blinding and placebo. Additionally, it is unclear if the effects are due to vitamin B6, other ingredients, or the combination.
Cataracts. Oral vitamin B6 does not seem to slow cataract development. Details: Clinical research in females with existing cardiovascular disease (CVD) or at increased risk of CVD shows that taking a combination of folic acid 2.5 mg, vitamin B6 (form not specified) 50 mg, and vitamin B12 1 mg daily for an average of 7.3 years does not reduce the risk of cataracts when compared with placebo. Furthermore, the risk of cataract extraction was increased by 28% (96149).
Chemotherapy-induced acral erythema. While some conflicting evidence exists, most research suggests that oral or topical vitamin B6 does not seem to prevent or reduce the severity of acral erythema induced by chemotherapy. Details: A meta-analysis of 10 clinical trials and 4 observational studies shows that taking vitamin B6 60-500 mg daily for up to 8 chemotherapy cycles does not prevent chemotherapy-induced acral erythema or reduce the incidence of severe cases when compared with control. Most studies used capecitabine chemotherapy alone or in combination, and one study used pegylated liposomal doxorubicin; however, no subgroup analysis was conducted to differentiate chemotherapy regimens. Results did not seem to vary based on study location, study design, or vitamin B6 dose (104930). However, a more recent preliminary clinical study in patients receiving doxorubicin for multiple myeloma shows that taking vitamin B6 100 mg on the first day of chemotherapy then twice daily for 7 days with each cycle reduces the risk of developing acral erythema by 72%, but does not improve the severity of acral erythema, when compared with no vitamin B6 supplementation (110458). Also, one small, low-quality clinical study suggests that taking vitamin B6 400 mg daily reduces the risk of moderate or severe chemotherapy-induced acral erythema when compared with vitamin B6 200 mg daily; however, the higher dose also seems to be associated with worsened tumor response and increased treatment failure (97620). Topical vitamin B6 has also failed to show benefit. A small clinical study in patients with acral erythema from capecitabine or pegylated liposomal doxorubicin shows that applying vitamin B6 1% cream to affected areas three times daily for 6 weeks does not improve symptoms when compared with placebo (104929).
Colorectal adenoma. Oral vitamin B6 does not seem to reduce the risk of developing colorectal adenomas. Details: Clinical research shows that taking a combination of B vitamins, including folic acid 2.5 mg, vitamin B6 (pyridoxine) 50 mg, and vitamin B12 1 mg, daily for up to 9.2 years does not reduce the risk of colorectal adenoma in females at high risk of cardiovascular disease when compared with placebo (90389).
Eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of eclampsia when compared with control (83046,96166).
Osteoporosis. Oral vitamin B6 does not seem to reduce the risk of osteoporotic fractures. Details: Clinical research in patients with cerebrovascular disease shows that taking a combination of B vitamins, including folic acid 2 mg, vitamin B6 (form not specified) 25 mg, and vitamin B12 500 mcg daily for up to 10.5 years does not prevent osteoporotic fractures when compared with placebo (90377). Furthermore, a secondary analysis of two large studies in patients with cardiovascular disease has found that taking vitamin B6 (pyridoxine) 40 mg daily in addition to folic acid and vitamin B12 for 1-3 years is associated with a 42% increased risk of hip fracture over an 11-year period when compared with only folic acid and vitamin B12 (96163). This finding is limited because these studies were not designed to assess the effects of vitamin B6 on fracture risk and the analyses were not adjusted for baseline bone health or fall risk.
Pre-eclampsia. Oral or intramuscular vitamin B6 does not seem to reduce the risk of pre-eclampsia. Details: Meta-analyses of limited clinical research in pregnant patients show that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of pre-eclampsia when compared with placebo (83046,96166).
Preterm labor. Oral or intramuscular vitamin B6 does not seem to reduce the risk of preterm labor. Details: Meta-analyses of limited clinical research in pregnant patients shows that taking vitamin B6 (pyridoxine), either as 25 mg daily or a single dose of 100 mg orally or intramuscularly, does not reduce the risk of preterm labor when compared with placebo (83046,96166).

INSUFFICIENT RELIABLE EVIDENCE to RATE

Acne. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in adults and children with inflammatory acne shows that taking 1-4 tablets of a specific product (NicAzel, Elorac Inc.) containing vitamin B6 (pyridoxine), nicotinamide, azelaic acid, zinc, copper, and folic acid for 8 weeks reduces inflammatory lesions and improves appearance in 88% and 81% of patients, respectively, when compared to baseline (90800). The validity of these findings is limited by the lack of a comparator group.
Age-related macular degeneration (AMD). Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A large-scale clinical study shows that taking vitamin B6 (pyridoxine) 50 mg, vitamin B12 1000 mcg, and folic acid 2.5 mg daily reduces the risk for AMD in females over 40 years of age with a history of cardiovascular disease (CVD) or with risk factors for CVD. Those who took this combination for an average of 7.3 years had a 34% reduced risk of developing AMD and a 41% reduced risk of visually significant AMD when compared with placebo (14620). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
Angioplasty. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Some evidence suggests that vitamin B6 (pyridoxine) 10 mg, folic acid 1 mg, and vitamin B12 400 mcg daily can decrease the rate of restenosis in patients treated with balloon angioplasty (8009,9412). However, this combination does not seem to be as effective for reducing restenosis in patients after coronary stenting (8009). An intravenous loading dose of folic acid, vitamin B6 (pyridoxine), and vitamin B12 followed by oral administration of folic acid 1.2 mcg, vitamin B6 (pyridoxine) 48 mg, and vitamin B12 60 mcg daily after bare metal coronary stenting also does not seem to reduce restenosis and might actually increase restenosis (12150,12151). Due to the lack of evidence of benefit and potential for harm, this combination of vitamins should not be recommended for patients receiving coronary stents (12151). It is unclear if any effects are due to vitamin B6, other ingredients, or the combination.
Antipsychotic-induced metabolic side effects. It is unclear if oral vitamin B6, as an adjunct to progesterone, is beneficial in patients with antipsychotic-induced amenorrhea. Details: A small clinical study in females with antipsychotic-induced amenorrhea shows that taking vitamin B6 80 mg three times daily for 1 month plus intramuscular progesterone daily for 5 days increases levels of estradiol and follicle stimulating hormone, reduces prolactin levels, and increases the rate of clinical efficacy, defined as the normalization of menstruation and improvement in endocrine indicators, by 14% when compared with progesterone alone (110457).
Anxiety. It is unclear if oral vitamin B6 is beneficial in patients with anxiety. Details: Clinical research in college students shows that taking vitamin B6 100 mg daily for one month does not reduce anxiety scores when compared with placebo (110453). However, because a diagnosis of anxiety was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with anxiety.
Asthma. It is unclear if oral vitamin B6 is beneficial in patients with asthma. Details: Preliminary clinical studies show that taking vitamin B6 (pyridoxine) 200-300 mg daily may improve symptoms of asthma in some patients, but not others, when compared with placebo (7064,7065). Studies have yielded conflicting results, with some research suggesting that it may only be beneficial in children with severe asthma (7065). Additionally, some research suggests that theophylline may lower vitamin B6 levels, although it is unclear if vitamin B6 supplementation is beneficial (4522,7066,9503).
Atherosclerosis. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with intermediate risk for coronary heart disease shows that taking a specific supplement (Kyolic, Total Heart Health, Formula 108, Wakunga) containing vitamin B6 12.5 mg, aged garlic extract 250 mg, vitamin B12 100 mcg, folic acid 300 mcg, and L-arginine 100 mg daily for 12 months reduces coronary artery calcium progression when compared with placebo (88385). It is unclear if this effect is due to vitamin B6, other ingredients, or the combination.
Atopic dermatitis (eczema). It is unclear if oral vitamin B6 is beneficial in patients with eczema. Details: A small clinical study in children with eczema shows that taking vitamin B6 (pyridoxine hydrochloride) 50 mg daily for 4 weeks does not reduce symptoms such as redness and itchiness when compared with placebo (83090).
Attention deficit-hyperactivity disorder (ADHD). It is unclear if oral vitamin B6 is beneficial for ADHD. Details: A small crossover study in children with ADHD shows that taking vitamin B6 600 mg, niacinamide and ascorbic acid 3 grams, and calcium pantothenate 1.2 grams daily for 6 weeks does not improve behavior scores when compared with placebo (9957).
Autism spectrum disorder. Although there is interest in using oral vitamin B6 for autism, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Bipolar disorder. It is unclear if oral vitamin B6 is beneficial in patients with bipolar disorder. Details: A small clinical trial in patients with type 1 bipolar disorder who are taking lithium and experiencing an acute episode of mania shows that taking vitamin B6 80 mg daily for 8 weeks does not improve cognitive function or the severity of mania when compared with placebo. Cognitive function was reduced in patients taking vitamin B6; any effect on sleep was unclear (107132).
Cancer. It is unclear if oral vitamin B6 reduces overall cancer risk. Details: Population research has found that higher dietary intake of vitamin B6 is associated with a 22% reduced risk of cancer, including esophageal, pancreatic, gastric, colorectal, and breast cancer. However, when dietary and supplemental vitamin B6 intake is considered, the inverse association between vitamin B6 and cancer risk is weaker and limited to fewer tumor sites. Furthermore, a meta-analysis of 9 clinical studies shows that taking vitamin B6 3-100 mg orally daily for 2-7.3 years, in combination with vitamin B12 and folate, does not reduce the risk of cancer in patients with cardiovascular disease or kidney failure (96164).
Cardiovascular disease (CVD). Oral vitamin B6, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly lower the risk of stroke. Details: Overall evidence from clinical research and meta-analyses shows that taking vitamin B6 in combination with folic acid and/or vitamin B12 does not seem to help with secondary prevention of death or myocardial infarction in patients with or at risk for CVD (11387,13482,34540,50423,83050,90379,97619). In fact, some research suggests that long-term supplementation with vitamin B6, folic acid, and vitamin B12 for secondary prevention increases the risk of CVD by 20% despite lowering homocysteine levels by 30% (13482). However, some research shows that taking vitamin B6 in combination with other B vitamins modestly reduces the risk of stroke, although results are conflicting (11387,13482,50423,83050,96150,96165,97619,107136). Additionally, it is unclear which specific combination of B vitamins is optimal for reducing stroke risk and which patients are most likely to benefit. In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) approved a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368).
Cognitive function. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A moderate-sized clinical study in healthy adults aged 40-65 years shows that taking a supplement containing vitamin B6, ginkgo leaf, bacopa, and other B vitamins twice daily for 12 weeks does not improve memory or attention when compared with placebo (111334).
Colorectal cancer. It is unclear if oral vitamin B6 reduces the risk of colorectal cancer. Details: A meta-analysis of observational studies suggests that the highest dietary intake of vitamin B6 is associated with a 20% reduced risk of colorectal cancer when compared with the lowest dietary intake. However, this association was not shown in subgroup analyses of studies conducted in Australia, Europe, or North America (111600). The validity of this analysis is limited by the heterogeneity of the included studies.
Dental caries. There is limited evidence on the oral use of vitamin B6 for dental decay during pregnancy. Details: Meta-analyses of limited clinical research show that taking vitamin B6 (pyridoxine), 25 mg daily or a single dose of 100 mg orally or intramuscularly, may reduce the risk of dental decay during pregnancy when compared with placebo (83046,96166).
Depression. It is unclear if oral vitamin B6 reduces the risk of developing depression or improves symptoms of depression. Details: Clinical research in healthy college students shows that taking vitamin B6 100 mg daily for one month does not reduce depression scores when compared with placebo (1104453). However, because a diagnosis of depression was not a requirement for study participation, it is unclear if these findings can be generalized to patients diagnosed with depression. Whether vitamin B6 reduces the risk of developing depression is also unclear. A meta-analysis of population research has found that the highest dietary intake of vitamin B6 is associated with a 19% lower risk of depression when compared with the lowest intake. However, sub-analyses suggest that this association is only relevant in females and not males (107133). In one individual population study in community dwelling older adults included in the analysis, the consumption of at least 1.71 mg of vitamin B6 daily from food was associated with a 43% reduction in the likelihood of becoming depressed when compared with the consumption of 1.33 mg or less daily in females. However, there was no association between vitamin B6 levels and risk of depression in males, and the finding in females was no longer significant when adjusted for total energy intake, since foods rich in vitamin B6 are energy-dense (96168). Another observational longitudinal study in healthy adults starting oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 40% lower risk of depression when compared with no supplementation (90789). Most available studies are cross-sectional in nature, making any conclusions related to causation difficult.
Diabetes. It is unclear if oral vitamin B6 is beneficial in patients with type 2 diabetes or gestational diabetes. Details: Observational research in Chinese adults with type 2 diabetes has found that dietary intake of vitamin B6 in the highest quartile is associated with 53% lower odds of developing cardiovascular disease, defined as a non-fatal myocardial infarction, non-fatal stroke, or hospitalization for unstable angina, when compared with vitamin B6 intake in the lowest quartile (110452). Small clinical studies in patients with gestational diabetes and vitamin B6 deficiency shows that taking vitamin B6 (pyridoxine) 100 mg daily for 2 weeks improves glucose tolerance and blood glucose levels when compared with baseline (82967,83088). However, there is concern that these findings were confounded by dietary alterations. This benefit was not observed in a subsequent small case series in patients with gestational diabetes (22380).
Diabetic neuropathy. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research suggests that taking a combination of B vitamins, including folic acid (L-methylfolate), vitamin B12 (methylcobalamin), and vitamin B6 (pyridoxal-5'-phosphate) for 24 weeks does not improve neural dysfunction based on vibration perception when compared with placebo in patients with diabetic neuropathy. However, taking this combination appears to modestly improve neuropathy symptoms and quality of life related to mental functioning when compared with placebo (90375).
Dysmenorrhea. It is unclear if oral vitamin B6 is beneficial in patients with dysmenorrhea. Details: Preliminary clinical research shows that taking vitamin B6 (form not specified) 200 mg daily reduces pain associated with dysmenorrhea when compared with placebo. However, taking vitamin B6 in combination with magnesium does not reduce pain when compared with placebo (77388).
Fibromyalgia. It is unclear if oral vitamin B6 is beneficial in patients with fibromyalgia. Details: A small clinical study in patients with fibromyalgia shows that taking vitamin B6 80 mg daily for 8 weeks does not improve pain, disease severity, anxiety, depression, or quality of life when compared with placebo (110454).
Gastroenteritis-associated nausea and vomiting. It is unclear if oral vitamin B6 is beneficial in children with gastroenteritis. Details: A small clinical study in children aged 6 months to 12 years with acute viral gastroenteritis shows that taking vitamin B6 (form not specified) does not improve symptoms of dehydration or the frequency of vomiting when compared with placebo (90793).
Helicobacter pylori. It is unclear if oral vitamin B6 is beneficial for Helicobacter pylori. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy does not improve eradication rates when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding.
Hypertension. It is unclear if oral vitamin B6 reduces blood pressure. Details: One small clinical study in patients with essential hypertension shows that taking vitamin B6 (pyridoxine hydrochloride) 5 mg/kg daily for 4 weeks can reduce systolic and diastolic blood pressure when compared with baseline (83091). The validity of this finding is limited by the lack of a control group.
Hypertriglyceridemia. It is unclear if oral vitamin B6 reduces triglyceride levels. Details: Preliminary clinical research shows that vitamin B6 (form not specified) 50 mg daily for 12 weeks does not reduce triglyceride levels in people with hypertriglyceridemia when compared with placebo. However, vitamin B6 appears to decrease total cholesterol and high-density lipoprotein (HDL) cholesterol by approximately 9% in these patients (59028).
Infertility. Although there is interest in using oral vitamin B6 for infertility, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Insomnia. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in healthy adults with self-reported sleep difficulty shows that taking a specific product (LZ Complex3, Sanofi Consumer Healthcare Pty Ltd.) containing vitamin B6, zizyphus extract, hops extract, hydrolyzed milk protein (Lactium), and magnesium oxide nightly, 30 minutes before bed, for 2 weeks does not improve sleep quality, daytime functioning, or physical fatigue when compared with placebo. However, due to the large improvement seen in both the treatment and placebo groups, the effectiveness of this product is unclear (95971).
Isoniazid-induced neuropathy. It is unclear if oral vitamin B6 prevents the development of neuropathy in patients taking isoniazid. Details: Preliminary clinical research in patients taking isoniazid for tuberculosis shows that taking vitamin B6 (pyridoxine) 6 mg daily reduces the development of neuropathy when compared with control (83068).
Lactation. It is unclear if oral vitamin B6 helps to suppress postpartum lactation. Details: A meta-analysis of two small clinical trials shows that taking vitamin B6 (pyridoxine) 400-600 mg daily for 6-7 days postpartum does not suppress lactation when compared with no treatment (83047).
Levetiracetam-induced side effects. While some conflicting evidence exists, several small, low-quality studies suggest that oral vitamin B6 (pyridoxine) may reduce some neuropsychiatric adverse effects related to the use of levetiracetam. Details: In an analysis of case reports, retrospective studies, and a single low-quality prospective study, improvement in levetiracetam-associated neuropsychiatric symptoms occurred in approximately 73% of patients taking pyridoxine (107137). A more recent preliminary clinical trial in children ages 1-17 years shows that taking pyridoxine 10 or 15 mg/kg daily as needed based on symptoms improves behavioral side effects associated with levetiracetam by a small amount when compared with low-dose pyridoxine 0.5 mg/kg daily used as placebo (107124). Also, observational research in children ages 9 months to 14 years has found that taking vitamin B6 is associated with improved behavior and a 44% lower risk of levetiracetam discontinuation when compared with no vitamin B6 supplementation (110455). Some observational research in adults with levetiracetam-associated irritability has found that taking vitamin B6 is associated with an improvement in irritability in 45% of patients when compared to baseline (107129). However, a small clinical trial in adults with epilepsy shows that taking pyridoxine 40 mg daily for 3 weeks does not improve levetiracetam-related psychiatric adverse effects when compared with placebo (110456). This study may have been underpowered to detect differences between groups. Pyridoxine doses used in the studies above have ranged from 50-400 mg daily in children and 40-600 mg daily in adults (107124,107129,107137,110456).
Lung cancer. It is unclear if dietary or oral vitamin B6 reduces lung cancer risk. Details: Epidemiological research has found that higher serum levels of vitamin B6 in male smokers is associated with a lower risk of lung cancer (9454). Also, people with blood levels of vitamin B6 in the top quartile have a modestly lower risk of lung cancer when compared with those whose levels are in the lowest quartile. The association is stronger for males and for people who have smoked (97999). However, other epidemiological research found that increased dietary intake of vitamin B6 is not associated with a reduced risk of lung cancer (96164).
Menopausal symptoms. Although there is interest in using oral vitamin B6 for menopausal symptoms, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Motion sickness. Although there is interest in using oral vitamin B6 for motion sickness, there is insufficient reliable information about the clinical effects of vitamin B6 for this condition.
Nausea and vomiting. It is unclear if oral vitamin B6 is beneficial for nausea and vomiting in patients taking oral contraceptives or antibiotics for Helicobacter pylori. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy reduces the incidence and severity of gastrointestinal adverse effects when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding. An observational longitudinal study in healthy females taking oral contraceptives containing ethinyl estradiol and levonorgestrel has found that taking vitamin B6 25 mg daily for 6-12 months is associated with a 43% reduced risk of nausea when compared with no supplementation (90789).
Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B6 for patients with NAFLD. Details: A small clinical trial in patients with NAFLD shows that taking vitamin B6 (pyridoxine) 30 mg three times daily for 12 weeks does not reduce levels of liver transaminases or plasma lipids when compared with baseline. However, hepatic fat accumulation was modestly reduced (107130). The validity of this study is limited by the lack of a comparator group.
Obesity. It is unclear if oral vitamin B6 in beneficial in overweight or obese individuals. Details: A small clinical trial in females with a body mass index (BMI) of at least 25 kg/m² shows that taking vitamin B6 as pyridoxine 80 mg daily for 8 weeks reduces fat mass and improves insulin resistance and triglyceride levels by a small amount when compared with placebo. Although some other anthropometric and metabolic indices were improved when compared with baseline, there was no effect of pyridoxine on body weight, visceral adiposity, or other endpoints when compared with placebo (107131).
Overall mortality. It is unclear if oral vitamin B6 reduces the risk of overall mortality. Details: Observational research in US adults has found that dietary intake of vitamin B6 in the highest quintile is associated with a 12% to 21% lower risk of all-cause mortality and a 31% to 44% lower risk of cardiovascular mortality when compared with the lowest quintile of dietary vitamin B6 intake (110451).
Pancreatic cancer. It is unclear if oral vitamin B6 reduces the risk of pancreatic cancer. Details: Observational research has found that higher dietary intake of vitamin B6 is associated with a 37% lower risk of developing pancreatic cancer when compared with lower intake (104927).
Postpartum depression. It is unclear if oral vitamin B6 is beneficial in patients with postpartum depression. Details: Preliminary clinical research in individuals considered at increased risk for postpartum depression, but without clinical depression, shows that taking vitamin B6 80 mg daily from the 28th week of pregnancy until birth, and then 40 mg daily for one month, reduces symptoms of depression 1.5 months after birth when compared with baseline (measured during the third trimester) and when compared with placebo. However, it is unclear if any of the patients included in the study developed postpartum depression, as there were no changes in overall symptoms in patients taking placebo (107126).
Proton pump inhibitor-induced gastrointestinal (GI) symptoms. It is unclear if oral vitamin B6 is beneficial for proton pump inhibitor-induced GI symptoms. Details: A large clinical study in adults with Helicobacter pylori infection shows that taking vitamin B6 20 mg twice daily for 2 weeks alongside conventional quadruple therapy reduces the incidence and severity of gastrointestinal adverse effects when compared with a control group not receiving vitamin B6 (113551). Conventional therapy consisted of a proton pump inhibitor, bismuth, minocycline, and metronidazole. The validity of this study is limited by the lack of placebo and inadequate blinding.
Restless legs syndrome (RLS). It is unclear if oral vitamin B6 is beneficial in patients with RLS. Details: A small clinical study in adults with RLS who are beginning treatment with pramipexole shows that also taking vitamin B6 40 mg daily for 2 months moderately improves RLS scores and sleep quality scores when compared with pramipexole and placebo (110052).
Schizophrenia. It is unclear if oral vitamin B6 is beneficial for patients with treatment-resistant schizophrenia. Details: Clinical research in male patients with treatment-resistant schizophrenia who are on a consistent antipsychotic dose shows that adding vitamin B6 300 mg twice daily for 16 weeks modestly improves psychotic symptoms and some measures of cognitive performance when compared with adding aripiprazole 5 mg twice daily (107128). More research is needed to determine if these benefits are clinically relevant.
Seizures. It is unclear if oral vitamin B6 is beneficial for preventing seizures in patients with glycosylphosphatidylinositol (GPI) deficiency. Details: Observational case series in a small number of children and young adults with GPI deficiency has found that taking vitamin B6 20-30 mg/kg daily for 3-12 months is associated with some reduction in seizure frequency in 9 of 13 patients. However, no patient reached seizure freedom (107125,107135). In one case series, treatment for 12 months was associated with modest developmental improvements in almost all patients (107135). The study patient populations were slightly different in terms of age and underlying genetic causes for GPI deficiency.
Sickle cell disease. Oral vitamin B6 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear. Details: Preliminary clinical research in adults with sickle cell disease shows that taking vitamin B6 4.2-6 mg, vitamin B12 4.2-6 mcg, and folic acid 700 mcg daily might lower homocysteine levels. However, it is unknown if this will reduce the risk of endothelial damage in these patients (9324).
Stroke. It is unclear if oral vitamin B6, either alone or with other B vitamins, is beneficial for stroke prevention. Details: There is some debate about whether supplementation with homocysteine-lowering B vitamins, including vitamin B6, can reduce the risk of stroke. A number of clinical studies and meta-analyses show that supplementation with folic acid, vitamin B6, and vitamin B12, alone or in combination, does not reduce the risk of stroke in patients with cardiovascular disease (CVD) or impaired kidney function (11387,13482,50423,83050,96150). However, a more recent meta-analysis of 10 clinical trials, including over 44,000 patients at risk for or with a history of CVD, shows that B vitamin supplementation reduces the relative risk of stroke by 10% when compared with placebo (97619). This meta-analysis differed from some of the earlier analyses due to the inclusion of several additional clinical trials. Also, another meta-analysis of three clinical trials including 9900 patients with a history of stroke shows that B vitamin supplementation reduces the relative risk of stroke recurrence by 13% when compared with placebo, although this finding was determined to have a low level of certainty. Based on two clinical trials, there was also a 17% reduced risk of vascular death and an 11% reduction in the combined risk of stroke, myocardial infarction, and vascular death (107136). In 2001, prior to the publication of the highest quality research on this topic, the US Food and Drug Administration (FDA) allowed a qualified health claim stating that, as part of a well-balanced diet that is low in saturated fat and cholesterol, folic acid, vitamin B6, and vitamin B12 may reduce the risk of vascular disease (102368). Unfortunately, even after the publication of higher quality research, it is still unclear which specific combination of B vitamins is optimal and which patients are most likely to benefit. One network meta-analysis shows that a combination of folic acid and vitamin B6 lowers the risk of stroke more effectively than B vitamin mixtures that include vitamin B12 (96165). However, this analysis is limited because it didn't account for dosing. Exposure to low, but not high amounts, of vitamin B12 (cyanocobalamin) seems to reduce stroke risk (96150).
Tardive dyskinesia. It is unclear if oral vitamin B6 prevents tardive dyskinesia in patients taking neuroleptic drugs. Details: A small clinical study in patients taking neuroleptic drugs for schizophrenia shows that taking vitamin B6 (form not specified) 400 mg daily seems to improve Parkinsonian, dystonic, and dyskinetic symptoms when compared with placebo (8558).
Tourette syndrome. Oral vitamin B6 has only been evaluated in combination with other ingredients; its effect when used alone is unclear. 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 vitamin B6 2.8 mg and L-theanine 200 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.
Vincristine-induced neuropathy. Oral vitamin B6 has only been evaluated in combination with pyridostigmine; its effect when used alone is unclear. Details: A small clinical study in children ages 11 months to 13 years with neuropathy due to vincristine treatment for acute lymphoblastic leukemia, shows that taking vitamin B6 150 mg/m2 and pyridostigmine 3 mg/kg twice daily for 3 months is associated with reduced severity of sensory and motor neuropathy when compared with baseline (104928). The validity of this finding is limited by the lack of a control group. More evidence is needed to rate vitamin B6 for these uses.

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Safety view details

Below is general information about the safety of the known ingredients contained in the product GabaRest. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

GAMMA-AMINOBUTYRIC ACID (GABA) (GABA)

LIKELY SAFE ...when used orally in amounts commonly found in foods.

POSSIBLY SAFE ...when used orally in medicinal amounts, short-term. GABA has been used with apparent safety in doses of 75 mg to 1.5 grams daily for up to one month in small clinical studies (19361,19363,19369,110134,110135). There is insufficient reliable information available about the safety of GABA when used orally for longer than one month or when used sublingually or intravenously.

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

HOPS

LIKELY SAFE ...when consumed in amounts commonly found in foods. Hops extract and hops oil have Generally Recognized as Safe (GRAS) status in the US (4912).

POSSIBLY SAFE ...when hops extract and hops-derived bitter acids are used orally and appropriately for medicinal purposes, short-term. Hops extract has been used with apparent safety in doses of up to 300 mg daily for 2-3 months. Hops-derived bitter acids have been used with apparent safety at a dose of 35 mg daily for 3 months (12,55338,55370,102899,105953,107813).

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

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PASSION FLOWER (Passionflower)

LIKELY SAFE ...when used orally as a flavoring in foods. The US Food and Drug Administration (FDA) lists passion flower as a permitted food flavoring additive, to be used in the minimum quantity necessary (91203).

POSSIBLY SAFE ...when used orally and appropriately in medicinal amounts, short-term. Passion flower extract has been used with apparent safety at doses up to 800 mg daily for up to 8 weeks (88198,102866). A specific passion flower extract (Pasipay, Iran Darouk Pharmaceutical Company) has been safely used at a dose of 45 drops daily for up to one month (8007,95036). Also, a tea prepared by steeping 2 grams of the dried aerial parts of passion flower in 250 mL of boiling water for 10 minutes has been used nightly for 7 nights (17374). There is insufficient reliable information available about the safety of passion flower when used topically.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. A specific passion flower product (Pasipay, Iran Darouk Pharmaceutical Company) has been used safely in children aged 6-13 years at a dose of 0.04 mg/ kg daily for 8 weeks (88197).

PREGNANCY: POSSIBLY UNSAFE
when used orally. Some case reports suggest that passion flower use during the first and second trimesters of pregnancy may be associated with an increased risk for premature rupture of membranes and meconium aspiration syndrome; however, causality has not been confirmed (97279). The alkaloids harman and harmaline, which are sometimes found in passion flower, have been reported to have uterine stimulant activity (4,11020,95037). It is not known whether these constituents are present in sufficient quantities to have an effect.

LACTATION:
Insufficient reliable information available; avoid using.

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THEANINE (L-Theanine)

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.

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VALERIAN

LIKELY SAFE ...when used orally and appropriately, short-term. Valerian 300-600 mg daily has been safely used in clinical studies in over 12,000 patients for up to 6 weeks (2074,3484,3485,4032,15018,17577,17578,19409,96242,103221)(104010,105718). There is insufficient reliable information available about the safety of valerian when used orally for longer than 6 weeks.

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. Valerian 160-320 mg has been used with apparent safety in children under 12 years of age for 4-8 weeks (14416).

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

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VITAMIN B6

LIKELY SAFE ...when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of 100 mg daily in the form of pyridoxine for adults (15,6243). ...when used parenterally and appropriately. Injectable vitamin B6 (pyridoxine) is an FDA-approved prescription product (15).

POSSIBLY SAFE ...when used orally and appropriately in doses of 101-200 mg daily (6243,8558).

POSSIBLY UNSAFE ...when used orally in doses at or above 500 mg daily. High doses, especially those exceeding 1000 mg daily or total doses of 1000 grams or more, pose the most risk. However, neuropathy can occur with lower daily or total doses (6243,8195). ...when used intramuscularly in high doses and frequency due to potential for rhabdomyolysis (90795).

CHILDREN: LIKELY SAFE
when used orally and appropriately in doses that do not exceed the tolerable upper intake level (UL) of vitamin B6 in the form of pyridoxine 30 mg daily for children aged 1-3 years, 40 mg daily for 4-8 years, 60 mg daily for 9-13 years, and 80 mg daily for 14-18 years (6243).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately in amounts exceeding the recommended dietary allowance (5049,8579,107124,107125,107135).

CHILDREN: POSSIBLY UNSAFE
when used orally in excessive doses, long-term (6243).

PREGNANCY: LIKELY SAFE
when used orally and appropriately. A special sustained-release product providing vitamin B6 (pyridoxine) 75 mg daily is FDA-approved for use in pregnancy. Vitamin B6 (pyridoxine) is also considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology (111601). However, it should not be used long-term or without medical supervision and close monitoring. The tolerable upper intake level (UL) refers to vitamin B6 in the form of pyridoxine and is 80 mg daily for those aged 14-18 years and 100 mg daily for 19 years and older (6243).

PREGNANCY: POSSIBLY UNSAFE
when used orally in excessive doses. There is some concern that high-dose maternal vitamin B6 (pyridoxine) can cause neonatal seizures (4609,6397,8197).

LACTATION: LIKELY SAFE
when used orally in doses not exceeding the tolerable upper intake level (UL) of vitamin B6 in the form of pyridoxine 80 mg daily for those aged 14-18 years and 100 mg daily for those 19 years and older. The recommended dietary allowance (RDA) in lactating women is 2 mg daily (6243). There is insufficient reliable information available about the safety of vitamin B6 when used in higher doses in breast-feeding women.

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Interactions with Drugs view details

Below is general information about the interactions of the known ingredients contained in the product GabaRest. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

GAMMA-AMINOBUTYRIC ACID (GABA) (GABA)

ANTIHYPERTENSIVE DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, taking GABA with antihypertensive drugs might increase the risk of hypotension.

Details

Some clinical research shows that GABA can decrease blood pressure in patients with hypertension (19367).

CNS DEPRESSANTS

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Theoretically, GABA might have additive sedative effects when used in conjunction with CNS depressants. However, it is unclear if this concern is clinically relevant.

Details

Endogenous GABA has well-established relaxant effects (51152) and GABA(A) receptors have an established physiological role in sleep (51143). However, the effects of GABA supplements are unclear, as it is unknown whether exogenous GABA crosses the blood-brain barrier (51120,51153,90570). Although there have been limited reports of drowsiness or tiredness with GABA supplements (5115,19364), these effects have not been widely reported in clinical studies. Additionally, intravenous GABA 0.1-1 mg/kg has been shown to induce anxiety in a dose-dependent manner (5116).

HOPS

CNS DEPRESSANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of hops with sedative drugs might cause additive sedation.

Details

Some animal research shows that hops has sedative effects (55415,55340,105930).

CYTOCHROME P450 1A2 (CYP1A2) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Hops extract does not seem to affect the metabolism of CYP1A2 substrates.

Details

In vitro research suggests that flavonoid constituents of hops inhibit CYP1A2 enzyme activity (10686). However, a pharmacokinetic study in healthy postmenopausal patients shows that taking a standardized extract of spent hops containing prenylated phenols, as 59.5 mg twice daily for 2 weeks, does not affect levels of caffeine, a CYP1A2 probe substrate (105954).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

Theoretically, hops extract might alter metabolism of CYP3A4 substrates; however, this effect may not be clinically significant.

Details

Animal research suggests that specific constituents of hops, called lupulones, can induce hepatic CYP3A4 enzyme activity (55325). However, a pharmacokinetic study in healthy postmenopausal patients with normal metabolism shows that taking a standardized extract of spent hops containing prenylated phenols, as 59.5 mg twice daily for 2 weeks, decreases the concentration of alprazolam, a CYP3A4 probe substrate, by 7.6%. This reduction is unlikely to be clinically relevant (105954).

ESTROGENS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Theoretically, concomitant use of large amounts of hops might interfere with hormone replacement therapy due to competition for estrogen receptors.

Details

In vitro research suggests that certain hops constituents can competitively bind to estrogen receptors (3701,10684,10685). However, most hops extracts contain very small amounts of these constituents (105930).

(Read more about HOPS)

PASSION FLOWER (Passionflower)

CNS DEPRESSANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Concomitant use of passion flower with sedative drugs might cause additive effects and side effects.

Details

Research in animals and humans shows that passion flower has sedative effects which can be additive when used with sedative medications like lorazepam (8007,19235,19236,19429,68309,104206).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Insignificant • Occurrence = Possible • Level of Evidence = D

Theoretically, passion flower might decrease the effects of CYP3A4 substrates.

Details

In vitro research suggests that passion flower can induce CYP3A4 enzymes, albeit to a much lower degree than rifampin, a known CYP3A4 inducer (110704).

ORGANIC ANION-TRANSPORTING POLYPEPTIDE SUBSTRATES (OATP)

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = D

Theoretically, passion flower might reduce the bioavailability of OATP2B1 and OATP1A2 substrates.

Details

In vitro research shows that the passion flower constituents apigenin and vitexin inhibit OATP2B1 and OATP1A2. This inhibition may be dose-dependent. One specific high-flavonoid passion flower extract (Valverde) seems to inhibit OATP2B1 and OATP1A2, while another extract with a lower flavonoid concentration (Arkocaps) shows less potent inhibition (105095). OATPs are responsible for the uptake of drugs and other compounds into the body; however, the specific activities of OATP2B1 and OATP1A2 are not well characterized.

(Read more about PASSION FLOWER)

THEANINE (L-Theanine)

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).

(Read more about THEANINE)

VALERIAN

ALCOHOL (Ethanol)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Valerian can have additive sedative effects when used concomitantly with alcohol.

Details

Valerian has sedative effects (9894). Theoretically, valerian might have an additive sedative effect when combined with alcohol. Excessive sedation has been reported in an alcohol-abusing individual who took valerian and Gingko biloba (19426). However, the potential interaction between valerian and alcohol has been disputed in other research. Limited evidence suggests that a combination of valerian 160 mg and lemon balm 80 mg (Euvegal) does not cause further deterioration in reaction ability and reaction rate when taken with alcohol as compared to the effects of alcohol alone (19427).

ALPRAZOLAM (Xanax)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = B

Valerian can have additive sedative effects when used with alprazolam. Also, valerian in high doses might modestly increase alprazolam levels, though this is not likely to be clinically significant.

Details

Valerian has sedative effects (9894). Theoretically, valerian might cause additive sedation when combined with alprazolam. Also, a small pharmacokinetic study shows that taking valerian extract 1000 mg daily (providing 11 mg valerenic acid) might increase alprazolam levels by about 19%. This might be due to valerian's mild inhibition of cytochrome P450 3A4 (CYP3A4) (13014). Despite being statistically significant, this increase is not likely to be clinically significant.

CNS DEPRESSANTS

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

Valerian can have additive sedative effects when used concomitantly with CNS depressant drugs.

Details

Theoretically, concomitant use of valerian and drugs with sedative and anesthetic properties may cause additive therapeutic and adverse effects (3486,12720,19429).

CYTOCHROME P450 2D6 (CYP2D6) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Unlikely • Level of Evidence = B

Valerian does not seem to have a clinically relevant effect on levels of drugs metabolized by CYP2D6.

Details

Although some in vitro evidence suggests that valerian affects CYP2D6, clinical pharmacokinetic (PK) studies show that valerian is unlikely to affect the CYP2D6 enzyme (13014,13536,19430,19431). In one PK study, taking valerian 1000 mg (providing about 11 mg valerenic acid) nightly for 14 days did not affect the metabolism of dextromethorphan, a CYP2D6 substrate. In another PK study, taking valerian 125 mg three times daily for 28 days did not affect metabolism of debrisoquine, an accepted CYP2D6 probe-substrate (13014,13536).

CYTOCHROME P450 3A4 (CYP3A4) SUBSTRATES

Interaction Rating = Minor Be watchful with this combination.

Severity = Mild • Occurrence = Possible • Level of Evidence = B

Valerian does not seem to have a clinically relevant effect on levels of drugs metabolized by CYP3A4.

Details

Although some in vitro evidence suggests that valerian extract might inhibit or induce CYP3A4, clinical pharmacokinetic (PK) studies show that valerian does not have a clinically significant effect on the CYP3A4 enzyme (6450,12214,13014,13536,19431). In one PK study, taking valerian 125 mg three times daily for 28 days did not affect metabolism of midazolam, an accepted CYP3A4 probe-substrate. In another PK study, taking valerian 1000 mg (providing about 11 mg valerenic acid) nightly for 14 days modestly increases levels of alprazolam, a CYP3A4 substrate, suggesting mild inhibition of CYP3A4 (13014,13536). However, this mild inhibition is unlikely to be clinically relevant.

GLUCURONIDATED DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = D

Valerian might weakly inhibit glucuronidation and increase concentrations of drugs metabolized by UGT1A1 and UGT2B7.

Details

In vitro research shows that methanolic valerian extract and valerenic acid might competitively inhibit UDP-glucuronosyltransferase (UGT) 1A1 (UGT1A1) and UGT2B7 (81685).

(Read more about VALERIAN)

VITAMIN B6

AMIODARONE (Cordarone)

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, vitamin B6 might increase the photosensitivity caused by amiodarone.

Details

Despite initial case reports suggesting that pyridoxine may have a protective effect against amiodarone-induced photosensitivity, preliminary clinical research suggests that pyridoxine may actually exacerbate this adverse effect (8892,8893).

ANTIHYPERTENSIVE DRUGS

Interaction Rating = Moderate Be cautious with this combination.

Severity = Moderate • Occurrence = Possible • Level of Evidence = B

Theoretically, vitamin B6 may have additive effects when used with antihypertensive drugs.

Details

Research in hypertensive rats shows that vitamin B6 can decrease systolic blood pressure (30859,82959,83093). Similarly, clinical research in patients with hypertension shows that taking high doses of vitamin B6 may reduce systolic and diastolic blood pressure, possibly by reducing plasma levels of epinephrine and norepinephrine (83091).

LEVODOPA

Interaction Rating = Minor Be watchful with this combination.

Severity = Moderate • Occurrence = Unlikely • Level of Evidence = D

Vitamin B6 may increase the metabolism of levodopa when taken alone, but not when taken in conjunction with carbidopa.

Details

Vitamin B6 (pyridoxine) enhances the metabolism of levodopa, reducing its clinical effects. However, this interaction does not occur when carbidopa is used concurrently with levodopa (Sinemet). Therefore, it is not likely to be a problem in most people (3046).

PHENOBARBITAL (Luminal)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

High doses of vitamin B6 may reduce the levels and clinical effects of phenobarbital.

Details

Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenobarbital, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenobarbital to avoid high doses of vitamin B6 (3046,10801).

PHENYTOIN (Dilantin)

Interaction Rating = Moderate Be cautious with this combination.

Severity = High • Occurrence = Possible • Level of Evidence = D

High doses of vitamin B6 may reduce the levels and clinical effects of phenytoin.

Details

Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenytoin, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenytoin to avoid high doses of vitamin B6 (3046,10801).

(Read more about VITAMIN B6)

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Adverse Effects view details

Report an Adverse Reaction to GabaRest

Below is general information about the adverse effects of the known ingredients contained in the product GabaRest. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.

GAMMA-AMINOBUTYRIC ACID (GABA) (GABA)

General ...Orally, GABA seems to be generally well tolerated. Sublingually, no adverse effects have been reported. However, a thorough evaluation of safety outcomes has not been conducted.
Most Common Adverse Effects:
Orally: Drowsiness, gastric upset, minor throat burning, muscle weakness, and nausea.

Cardiovascular ...Intravenously, GABA can cause dose-related increases in blood pressure and pulse (5116).

Gastrointestinal ...Orally, minor throat burning has been associated with GABA in one study (5115). In another study in which GABA was administered with phosphatidylserine, one patient experienced severe gastric distress, two patients reported moderate nausea, and one reported constipation (19364). Children with cerebral palsy taking GABA experienced nausea and decreased appetite (19362).

Genitourinary ...In one study, one patient treated with oral GABA and phosphatidylserine reported transient amenorrhea (19364).

Musculoskeletal ...Orally, minor adverse effects associated with GABA included muscle weakness (5115).

Neurologic/CNS ...Orally, GABA may cause drowsiness, headache, or tiredness (5115,19364,112830). Four children with cerebral palsy taking GABA had convulsions, and an unspecified number experienced motor restlessness. However, causality of these adverse effects was not clear, and the dose of GABA was not specified (19362). Intravenously, GABA 50 mg has been associated with a "lack of alertness" in healthy female volunteers (51159).

Psychiatric ...Intravenously, GABA 0. 1-1.0 mg/kg has been shown to induce anxiety, dysphoria, and mood disturbances in a dose-dependent manner (5116).

Other ...In one study, patients taking GABA experienced a slight warming of the body (19370).

HOPS

General ...Orally, hops extract and oil are generally well tolerated when used in food amounts. Hops extract also seems to be well tolerated when used in supplemental amounts.
Most Common Adverse Effects:
Orally: Drowsiness, sedation.

Dermatologic ...Topically, allergic reactions have been reported after contact with the fresh hops plant and plant dust. Contact dermatitis is attributed to the pollen (4,12,105930).

Genitourinary ...Orally, supplements containing hops and soy have been associated with 4 cases of postmenopausal bleeding (55404). It is unclear if this effect is due to hops, soy, or the combination. Also, menstrual disturbances have been reported in female workers harvesting hops (10684,55405).

Neurologic/CNS ...Orally, hops might cause drowsiness and sedation. Historically, hops are thought to have sedative effects, since workers harvesting hops were observed to tire easily after oral contact with hop resin. The European Medicines Agency states that hops may have sedative effects; however, there is a lack of clinical research confirming that hops extract causes drowsiness and sedation (105930).

Pulmonary/Respiratory ...Occupational exposure to dust from hops, usually in combination with dust from other products, is associated with chronic respiratory symptoms such as dry cough, dyspnea, chronic bronchitis, and other occupational respiratory diseases (55333,55414).

(Read more about HOPS)

PASSION FLOWER (Passionflower)

General ...Orally, passion flower is well tolerated.
Most Common Adverse Effects:
Orally: Confusion, dizziness, hypersensitivity, and sedation.

Cardiovascular ...There is a case report involving a 34-year-old female who was hospitalized with severe nausea, vomiting, drowsiness, prolonged QT interval, and episodes of nonsustained ventricular tachycardia following use of passion flower extract tablets (Sedacalm, Bioplus Healthcare), 1500 mg on day 1 and 2000 mg on day 2 to relieve stress. All symptoms resolved within one week after passion flower was discontinued (6251).

Genitourinary ...The alkaloids harman and harmaline, which are sometimes found in small amounts in passion flower, have been reported to have uterine stimulant activity (4,11020,95037).

Hematologic ...Orally, passion flower has been reported to cause epistaxis in one clinical trial (95038). Vasculitis has also been reported with use of a specific herbal product (Relaxir) produced mainly from the fruits of passion flower (6).

Hepatic ...There is debate about whether passion flower contains cyanogenic glycosides. Several related Passiflora species do contain these constituents (3), including Passiflora edulis, which is associated with liver and pancreatic toxicity (7).

Immunologic ...An idiosyncratic hypersensitivity reaction characterized by urticaria and cutaneous vasculitis has been reported in a 77-year-old male with rheumatoid arthritis after taking a specific combination product that included passion flower extract (Naturest) (68308). It is unclear if these effects were caused by passion flower or other ingredients.
In clinical trials, passion flower has been reported to cause allergy symptoms including sinus irritation; however, the frequency of these events was statistically nonsignificant when compared to treatment with midazolam 15 mg (95038).

Musculoskeletal ...Orally, passion flower has been reported to cause muscle relaxation in a clinical trial (95038).

Neurologic/CNS ...Orally, sedation, dizziness, ataxia, and confusion have been reported in clinical trials. However, these events generally do not necessitate discontinuation (8007,15391,15392,95036,95038). Altered consciousness has been reported with use of a specific herbal product (Relaxir) produced mainly from the fruits of passion flower (6).

(Read more about PASSION FLOWER)

THEANINE (L-Theanine)

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)

VALERIAN

General ...Orally, valerian is generally well-tolerated.
Most Common Adverse Effects:
Orally: Dizziness, drowsiness, and mental slowness. Other reported side effects include headache, gastrointestinal upset, excitability, and vivid dreams. When used chronically and abruptly stopped, symptoms of withdrawal such as tachycardia, anxiety, irritability, and insomnia might occur. Advise patients to taper doses slowly after extended use.
Serious Adverse Effects (Rare):
Orally: Several case reports raise concerns about hepatotoxicity after the use of valerian and valerian-containing multi-ingredient dietary supplements. Withdrawal from chronic valerian use has been associated with cases of cardiac failure and hallucinations.

Cardiovascular ...When used orally in high doses for an extended period of time, valerian withdrawal has been associated with tachycardia and high output cardiac failure in one patient with a history of coronary artery disease (3487). Chest tightness has been reported for an 18-year-old female who took 40-50 capsules containing valerian 470 mg/capsule (659). A case of severe hypotension, suspected to be due to vasodilation, hypocalcemia, and hypokalemia, has been reported for a patient who injected an unknown quantity of a crude tap water extract of raw valerian root (81734).

Dermatologic ...Orally, valerian might rarely cause a rash. A case of valerian-related rash that resolved after valerian root discontinuation was reported in clinical research (19422).

Gastrointestinal ...Orally, valerian has been associated with increased incidence of gastrointestinal problems including diarrhea, nausea, vomiting, and stomach pain (15046,19406,19407,19422,110712). In one individual, taking 20 times the normal dose caused abdominal cramping (659).

Hepatic ...There have been several case reports of hepatotoxicity associated with the use of multi-ingredient oral preparations containing valerian (8243,96241). In one case report, a 57-year-old man presented with acute hepatitis after consuming a cold and flu remedy containing valerian 2 grams for 3 days; the remedy also contained white willow, elderberry, and horseradish. Although the use of the cold and flu remedy was discontinued one month prior to symptom presentation, the acute hepatitis was attributed to valerian root and treated with steroids (96241). It is possible, however, that some of these preparations may have been adulterated with hepatotoxic agents (8243).
Hepatotoxicity involving long-term use of single-ingredient valerian preparations has also been reported (3484,17578). Also, a case of a 38-year-old female with liver insufficiency and cirrhosis of a vascular parenchymal nature who developed hepatotoxic symptoms following valerian and ethyl-alcohol abuse has been reported (81697). Symptoms resolved and laboratory values normalized following intense plasmapheresis treatment. Another case of acute hepatitis characterized by elevated aminotransferases, mild fibrosis, and liver inflammation has been reported for a 50-year-old female who consumed valerian root extract 5 mL three times weekly along with 10 tablets of viamine, a product containing dry valerian extract 125 mg/tablet, for 2 months (81696). Because a variety of doses were used in these cases, and many people have used higher doses safely, these hepatotoxic reactions might have been idiosyncratic. Tell patients the long-term effect of valerian on liver function is unknown.

Musculoskeletal ...In a case report, combined intake of valerian and passionflower caused throbbing and muscular fatigue when taken concomitantly with lorazepam (19429).

Neurologic/CNS ...Orally, valerian might cause dizziness, headaches, fatigue, sleepiness, and mental dullness (3484,17578,19411,19422,81723,89407). The severity of adverse effects appears to increase with higher doses (19411). However, taking valerian extracts in doses up to 1800 mg does not appear to significantly affect mood or psychomotor performance (10424,15044). Valerian does not usually have a negative impact on reaction time, alertness, and concentration the morning after intake (2074,8296). Clinical research shows that a single dose of valerian root 1600 mg is not associated with any changes in sleepiness, reaction time, or driving performance within 1-4 hours after intake (96240). More serious side effects may occur when valerian is taken at higher doses. In one individual, 20 times the normal dose caused tremor of the hand and foot and lightheadedness (659). In a case report, combined intake of valerian and passionflower caused shaking of the hands and dizziness when taken concomitantly with lorazepam (19429).

Psychiatric ...Orally, valerian has been associate with reports of restlessness, excitability, uneasiness, agitation, and vivid dreams (3484,17578,19411,19422). Chronic use and rapid cessation can lead to withdrawal syndrome with symptoms of agitation, insomnia, and hallucinations (104003). There appears to be a trend towards increased severity of adverse effects with higher doses (19411). A case of acute hypomania has been reported for a 21-year-old female patient who took a valerian decoction in water each night for one month to treat subclinical anxiety. Symptoms included euphoric mood, rapid speech, and increased sociability and sexual interest. Following cessation of valerian use and treatment with quetiapine 100 mg daily for two weeks, the patient recovered (89405). In another case report, an 85-year-old male with mild cognitive impairment, major depression, anxiety, and chronic kidney disease presented to the emergency department with hallucinations, confusion, and agitation thought to be due to abrupt cessation after taking valerian 600 mg daily for about 6 months. The symptoms resolved in about 5 days (104003).

(Read more about VALERIAN)

VITAMIN B6

General ...Orally or by injection, vitamin B6 is well tolerated in doses less than 100 mg daily.
Most Common Adverse Effects:
Orally or by injection: Abdominal pain, allergic reactions, headache, heartburn, loss of appetite, nausea, somnolence, vomiting.
Serious Adverse Effects (Rare):
Orally or by injection: Sensory neuropathy (high doses).

Dermatologic ...Orally, vitamin B6 (pyridoxine) has been linked to reports of skin and other allergic reactions and photosensitivity (8195,9479,90375). High-dose vitamin B6 (80 mg daily as pyridoxine) and vitamin B12 (20 mcg daily) have been associated with cases of rosacea fulminans characterized by intense erythema with nodules, papules, and pustules. Symptoms may persist for up to 4 months after the supplement is stopped, and may require treatment with systemic corticosteroids and topical therapy (10998).

Gastrointestinal ...Orally or by injection, vitamin B6 (pyridoxine) can cause nausea, vomiting, heartburn, abdominal pain, mild diarrhea, and loss of appetite (8195,9479,16306,83064,83103,107124,107127,107135). In a clinical trial, one patient experienced infectious gastroenteritis that was deemed possibly related to taking vitamin B6 (pyridoxine) orally up to 20 mg/kg daily (90796). One small case-control study has raised concern that long-term dietary vitamin B6 intake in amounts ranging from 3.56-6.59 mg daily can increase the risk of ulcerative colitis (3350).

Hematologic ...Orally or by injection, vitamin B6 (pyridoxine) can cause decreased serum folic acid concentrations (8195,9479). One case of persistent bleeding of unknown origin has been reported in a clinical trial for a patient who used vitamin B6 (pyridoxine) 100 mg twice daily on days 16 to 35 of the menstrual cycle (83103). It is unclear if this effect was due to vitamin B6 intake.

Musculoskeletal ...Orally or by injection, vitamin B6 (pyridoxine) can cause breast soreness or enlargement (8195).

Neurologic/CNS ...Orally or by injection, vitamin B6 (pyridoxine) can cause headache, paresthesia, and somnolence (8195,9479,16306). Vitamin B6 (pyridoxine) can also cause sensory neuropathy, which is related to daily dose and duration of intake. Doses exceeding 1000 mg daily or total doses of 1000 grams or more pose the most risk, although neuropathy can occur with lower daily or total doses as well (8195). The mechanism of the neurotoxicity is unknown, but is thought to occur when the liver's capacity to phosphorylate pyridoxine via the active coenzyme pyridoxal phosphate is exceeded (8204). Some researchers recommend taking vitamin B6 as pyridoxal phosphate to avoid pyridoxine neuropathy, but its safety is unknown (8204). Vitamin B6 (pyridoxine) neuropathy is characterized by numbness and impairment of the sense of position and vibration of the distal limbs, and a gradual progressive sensory ataxia (8196,10439). The syndrome is usually reversible with discontinuation of pyridoxine at the first appearance of neurologic symptoms. Residual symptoms have been reported in patients taking more than 2 grams daily for extended periods (8195,8196). Daily doses of 100 mg or less are unlikely to cause these problems (3094).

Oncologic ...In females, population research has found that a median intake of vitamin B6 1. 63 mg daily is associated with a 3.6-fold increased risk of rectal cancer when compared with a median intake of 1.05 mg daily (83024). A post-hoc subgroup analysis of results from clinical research in adults with a history of recent stroke or ischemic attack suggests that taking folic acid, vitamin B12, and vitamin B6 does not increase cancer risk overall, although it was associated with an increased risk of cancer in patients who also had diabetes (90378). Also, in patients with nasopharyngeal carcinoma, population research has found that consuming at least 8.6 mg daily of supplemental vitamin B6 during treatment was associated with a lower overall survival rate over 5 years, as well as a reduced progression-free survival, when compared with non-users and those with intakes of up to 8.6 mg daily (107134).

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