PEA (Palmitoylethanolamide) & Glucosamine Sulfate by Lake Avenue Nutrition

LIKELY EFFECTIVE

• Osteoarthritis. Oral glucosamine sulfate taken for at least 4 weeks is modestly beneficial for improving pain and function in knee osteoarthritis. However, oral glucosamine hydrochloride seems to only be beneficial when used in combination with chondroitin and other ingredients. It is unclear if glucosamine can slow disease progression or improve symptoms in other forms of osteoarthritis. Details: Meta-analyses of the available research in adults with KNEE osteoarthritis show that taking glucosamine SULFATE 1500 mg daily for up to 3 years modestly improves pain and function when compared with placebo (14305,89521,94382,95785,99684). Individual studies show 28% to 41% pain reduction and 21% to 46% improvement in function when compared with placebo (7026,8942,12461,20084,94382). Some research suggests that glucosamine sulfate reduces pain similarly to various non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen 400 mg three times daily and piroxicam 20 mg daily. However, NSAIDs appear to relieve symptoms within 2 weeks, while glucosamine sulfate takes 4-8 weeks. Notably, glucosamine sulfate appears to sustain benefit for longer after treatment withdrawal when compared with piroxicam (2604,20094,20096). Other clinical research shows that glucosamine sulfate 1500 mg once daily for 6 months might be more effective for reducing symptoms than acetaminophen 1 gram three times daily or 650 mg once daily in patients with moderate knee osteoarthritis (13578,20098). However, not all research shows benefit. Small clinical studies suggest that glucosamine sulfate 1500 mg daily for 2-6 months may NOT work for severe, long-standing osteoarthritis (1330,11459). It is unclear if glucosamine sulfate can slow disease progression. A specific crystalline glucosamine sulfate product (Dona, Rotta Pharmaceuticals) taken as 1500 mg daily for up to 3 years seems to prevent joint space narrowing of greater than 0.5 mm by up to 54% when compared with placebo (7026,8942,13719,42420). In contrast, other glucosamine sulfate formulations have not consistently been shown to improve symptoms or prevent joint space narrowing when compared with placebo (14305,89558,94382,95788). It is unclear if the benefit seen with this specific product (Dona) is due to bias introduced by industry funding or due to a higher quality product (42492). Glucosamine products associated with quality concerns have demonstrated inconsistent benefits in research (8128,102116). Limited research on the use of a different salt, glucosamine HYDROCHLORIDE, has found no benefit for knee osteoarthritis. A meta-analysis of clinical research and two other clinical trials show that taking glucosamine hydrochloride 1500 mg daily for up to 18 months does not seem to reduce pain when compared with placebo (18344,89519,89521). However, one small, unblinded clinical study in patients with mild to moderate osteoarthritis shows that taking a combination of glucosamine hydrochloride 480 mg every 12 hours and celecoxib 200 mg daily reduces pain scores, osteoarthritis severity, and inflammatory markers to a greater extent than celecoxib alone (106883). There is mixed evidence of benefit when glucosamine hydrochloride is used with chondroitin. Clinical research in patients over 40 years of age shows that taking a noncommercial preparation of glucosamine hydrochloride 1500 mg daily in combination with chondroitin sulfate 1200 mg daily for 6-24 months does not reduce pain when compared with placebo. The placebo response in these studies was sometimes as high as 60% (13579,14809,42477). However, a large, prospective observational study in adults with knee or hip osteoarthritis suggests that taking glucosamine hydrochloride 500 mg and chondroitin sulfate 400 mg (Theraflex, Bayer) three times daily for the first 3 weeks then twice daily thereafter for up to 64 weeks is associated with reductions in pain, stiffness, and the need for concomitant analgesic therapy and improvements in daily function and knee- or hip-related quality of life when compared to baseline. The most pronounced improvements were from 16-24 weeks (111647). The validity of these effects is limited by subjective outcomes, a lack of control group, and the observational design of the study. Furthermore, another clinical trial shows that taking a prescription product available in Spain (Droglican, Bioibérica S.A.), providing a similar daily dose of glucosamine hydrochloride with chondroitin sulfate for 6 months is non-inferior to celecoxib 200 mg daily for relieving pain, but not stiffness or function (89516). Small clinical studies show that taking a specific combination product (Cosamin or Cosamin DS, Nutramax Laboratories) containing glucosamine hydrochloride 1500-2000 mg, low molecular weight chondroitin sulfate 1200-1600 mg, and manganese ascorbate 228-304 mg, in 2-3 divided doses daily for 2-6 months improves pain in patients with mild or moderate, but not severe, osteoarthritis when compared with placebo (4237,7169). A different combination product (Gurukosamin & Kondoroichin, Suntory Wellness Ltd.) containing glucosamine hydrochloride 1200 mg, chondroitin sulfate 60 mg, and quercetin glycosides 45 mg, taken daily for 16 weeks, also seems to improve symptoms of knee osteoarthritis when compared with placebo (42514). It is unclear if the findings of any of these studies are due to glucosamine, chondroitin, other ingredients, or the combination. Despite evidence suggesting differing benefit (89521,94382), head-to-head comparisons of glucosamine sulfate and glucosamine hydrochloride are limited, and it is not universally acknowledged that these salts have different effectiveness profiles. One large clinical study in patients with knee osteoarthritis shows that taking a specific product (Artrolive, Aché Laboratórios Farmacêuticos S.A.) containing glucosamine sulfate 500 mg and chondroitin sulfate 400 mg three times daily for 4 months seems to be no different for reducing pain when compared with taking glucosamine hydrochloride 500 mg and chondroitin sulfate 400 mg (Cosamin DS, Nutramax Laboratories, Inc.) three times daily (89520). This study was funded by the supplement manufacturer. Many meta-analyses have pooled studies of both glucosamine salts together, producing largely inconsistent results (94381,99683,99685,112444). Experts have conflicting stances on the use of glucosamine. The American College of Rheumatology (ACR) strongly recommends against the use of any glucosamine products for any form of osteoarthritis (102114). Conversely, the European Society of Clinical and Economic Aspects of Osteoarthritis (ESCEO) strongly recommends the use of pharmaceutical-grade glucosamine sulfate products, such as Dona (Rotta Pharmaceuticals), in patients with osteoarthritis. Additionally, the ESCEO provides a weak recommendation against the use of glucosamine in combination with chondroitin (102141). These differing recommendations seem to be related to interpretation of the evidence for pharmaceutical-grade products. The ACR has determined that the inconsistent evidence may indicate the presence of industry bias; the ESCEO has determined that the inconsistent evidence is due to inconsistent product quality. Limited research has found mixed benefit of using glucosamine on osteoarthritis of the SPINE, HIP, or HAND. In one study of patients with osteoarthritis of the lumbar spine, taking glucosamine sulfate (Dona, Rotta Pharmaceuticals) 1500 mg daily for 6 weeks reduced pain in more patients when compared with placebo (1316). However, in another study, using a different glucosamine sulfate product (Glucosamine Sulfate, PharmaNord) 1500 mg daily for 6 months did not reduce pain when compared with placebo (89562). In patients with hip osteoarthritis, taking glucosamine sulfate 1500 mg once daily for 2 years did not reduce symptoms or slow disease progression when compared with placebo (16717,20100); however, there was a high rate of hip replacement, which may have confounded results (16717,16718). In patients with erosive osteoarthritis of the hand, observational research has found that taking glucosamine sulfate (Dona, Rotta Pharmaceuticals) 1500 mg daily along with conventional therapy for 6 months is associated with reduced hand pain, a shorter duration of morning stiffness, and improved hand function when compared with conventional therapy alone (108897). Limited research has also evaluated INTRAMUSCULAR and TOPICAL glucosamine sulfate. A clinical study in patients with mild to moderate knee osteoarthritis (radiological stage I-III) shows that giving intramuscular glucosamine sulfate 400 mg twice per week for 6 weeks reduces the severity of symptoms when compared with placebo (2605). There is also a small study showing that a topical preparation of glucosamine sulfate in combination with chondroitin sulfate, shark cartilage, and camphor reduces osteoarthritis symptoms when compared with placebo. However, any symptom relief is most likely due to the counterirritant effect of camphor and not the other ingredients (10327,12467). There is no evidence that glucosamine is absorbed topically. Glucosamine sulfate does not seem to PREVENT osteoarthritis. Clinical studies in overweight healthy females aged 50-60 years shows that taking crystalline glucosamine sulfate 1500 mg orally daily for 2.5 years does not reduce the incidence of osteoarthritis after a 6-7 year follow-up; however, it may reduce the percentage of patients who experience knee joint space narrowing (95789,97053).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Aging skin. Topical N-acetyl glucosamine has only been evaluated in combination with niacinamide for reducing hyperpigmentation and liver skin spots on aging skin; its effect when used alone is unclear. Details: A clinical study in females ages 40-60 years with skin hyperpigmentation and solar lentigines (liver spots) primarily due to aging and sun exposure shows that applying a cream containing 2% N-acetyl glucosamine and 4% niacinamide to the face twice daily with sunscreen for 10 weeks decreases facial hyperpigmentation when compared with sunscreen alone (92721). The effect of N-acetyl glucosamine alone is unclear.
• Aromatase inhibitor-induced arthralgia. Oral glucosamine sulfate has only been evaluated in combination with chondroitin; its effect when used alone is unclear. Details: A small open-label clinical study in patients with aromatase inhibitor-induced arthralgia shows that taking a combination of glucosamine sulfate 1500 mg and chondroitin sulfate 1200 mg in 2-3 divided doses daily for 24 weeks improves pain when compared to baseline in postmenopausal adults with early stage breast cancer (89561). The validity of this finding is limited by a lack of control group.
• Back pain. Although there is interest in using oral glucosamine for back pain, there is insufficient reliable information about the clinical effects of glucosamine for this condition.
• Cancer. Some low-quality observational studies have inconsistently found that glucosamine may be associated with a lower risk of different cancers; however, better quality evidence is needed. Details: A meta-analysis of observational research has found that use of glucosamine with or without chondroitin is associated with a 7% to 12% lower risk of cancer when compared with no use of glucosamine. A subgroup analysis showed a reduction in the risk of colorectal cancer, but not other types of cancer (110625). Observational research report conflicting relationships between glucosamine and cancer. Some observational research in adults in the United Kingdom has found that taking glucosamine is associated with 4% higher risk of cancer over a median follow up for 13 years. However, a subgroup analysis showed a reduction in the risk of lung cancer (110627). Other observational research in adults in the United Kingdom has found that taking glucosamine is associated with a 5% reduced risk of cancer mortality over a median follow-up of around 12 years, with reductions specifically occurring in those with kidney, lung, and rectal cancers. However, glucosamine use was not linked to a reduced risk of mortality due to bladder, brain, breast, colon, ovarian, prostate, skin, stomach, thyroid, or uterine cancer (109645). These studies are limited by observational designs, which also did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine use also reported overall healthier lifestyle habits than those that were not taking glucosamine. Although some studies attempted to control for these differences, higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and the risk for cancer and/or cancer-related mortality. Of note, some researchers have called into question the results from observational research linking glucosamine use to a lower rate of cancer, claiming that these studies suffer from a high risk of selection bias (109646).
• Cardiovascular disease (CVD). It is unclear if oral glucosamine prevents fatal or non-fatal CVD events. Details: Some observational research of adults in the United Kingdom has found that taking glucosamine is associated with an overall 15% reduced risk for fatal and non-fatal CVD events, including coronary heart disease (CHD) and stroke (99682). However, this study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine use also reported overall healthier lifestyle habits than those that were not taking glucosamine. Conversely, an observational study in Chinese patients with osteoarthritis has found that glucosamine use is associated with a 10% increase in the risk of CVD events and a 12% increase in the risk of CHD, with no increase in the risk of stroke. The risk for these outcomes was greatest in patients with higher adherence to glucosamine and in those taking larger doses (109642). However, this study also did not clarify the form of glucosamine used or provide specifics related to the frequency or duration of use. Furthermore, glucosamine users were generally older, more likely to be on antihyperlipidemic or antiplatelet therapy, and more likely to have multiple comorbidities compared with non-users. Both studies attempted to control for the differences in characteristics between glucosamine users and non-users; despite this, higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and CVD risk.
• Colorectal adenoma. Oral glucosamine has only been evaluated in combination with chondroitin; its effect when used alone is unclear. Details: An observational study in older adults has found that taking glucosamine and chondroitin is associated with a 26% reduced risk of high-risk adenoma and 10% reduced risk of conventional adenoma when compared with not using these supplements. This benefit was not seen in a subgroup of younger females (104444). This study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use.
• Colorectal cancer. It is unclear if oral glucosamine reduces the risk of colorectal cancer. Details: A large, observational study in adults has found that regular use of oral glucosamine is not associated with a reduced risk of colorectal cancer over a median of 7 years of follow-up, regardless of sex, age, body mass index, smoking status, or non-steroidal anti-inflammatory drug use (108018). This study did not clarify the form or dose of glucosamine used or the frequency or duration of use.
• Coronavirus disease 2019 (COVID-19). It is unclear if oral glucosamine is beneficial for COVID-19. Details: A large observational study in adults suggests that regular glucosamine use over a median of 1.7 years is not linked to a lower odds of COVID-19 infection but is associated with a 20% lower risk of hospital admission and a 19% lower risk of mortality due to COVID-19 when compared with adults not using glucosamine (111649). This study did not clarify the form or dose of glucosamine used or the frequency or duration of use.
• Dementia. Observational studies suggest that long-term, regular glucosamine intake might reduce the risk of developing certain types of dementia. Details: An observational study has found that regularly taking glucosamine for an average of 8.9 years is associated with a 19% lower risk of developing dementia, including Alzheimer disease and vascular dementia (110630). Another large observational study in older adults without dementia suggests that regularly taking glucosamine for a median of 12 years is associated with an 18% lower risk of vascular dementia. However, habitual glucosamine consumption is not associated with a reduced risk of Alzheimer disease or frontotemporal dementia (112461).
• Depression. It is unclear if oral glucosamine hydrochloride reduces depression symptoms. Details: A small, open-label clinical trial in patients with unipolar depression shows that taking glucosamine hydrochloride 1 gram daily for 1 week, followed by 2 grams daily for 3 weeks, reduces scores on the Hamilton Rating Scale for Depression (HAM-D) and Montgomery-Asberg Depression Rating Scale (MADRS) by 31% or 33% when compared to baseline. However, only 20% of patients experienced a 50% or greater reduction in HAM-D scores, and there were no improvements in Clinical Global Impression scores (103281). The lack of a control group limits the validity of these findings.
• Diabetes. It is unclear if oral glucosamine reduces the risk of developing type 2 diabetes in adults. Details: Observational research in adults in the United Kingdom has found that glucosamine use is associated with a 17% lower risk of type 2 diabetes. The relationship between glucosamine use and diabetes appears to be even more pronounced in patients with high baseline levels of C-reactive protein, a marker of inflammation (103234). However, this study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine use also reported overall healthier lifestyle habits than those that were not taking glucosamine. Although this study attempted to control for these differences, higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and the risk for diabetes.
• Gout. It is unclear if oral glucosamine reduces the risk of developing gout. Details: Observational research in adults in the United Kingdom has found that glucosamine use is associated with a 19% lower risk of gout in females, but not males (109644). However, this study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine use also reported overall healthier lifestyle habits than those that were not taking glucosamine. Although this study attempted to control for these differences, higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and the risk for gout.
• Heart failure. It is unclear if oral glucosamine prevents heart failure. Details: A large, prospective observational study in adults without heart failure suggests that taking glucosamine regularly over a median of 9 years is associated with a 13% lower risk of developing heart failure when compared with adults not taking glucosamine (111646). This study did not clarify the form or dose of glucosamine used or the frequency or duration of use.
• Hyperlipidemia. It is unclear if oral glucosamine hydrochloride improves hyperlipidemia when used with conventional medicine. Details: Preliminary clinical research shows that glucosamine hydrochloride does not reduce cholesterol or triglyceride levels in patients with hyperlipidemia. A small crossover study in older adults taking simvastatin or atorvastatin shows that adding a specific glucosamine hydrochloride product (Artrox, Pfizer) 750 mg twice daily for 4 weeks does not seem to affect lipid levels when compared with placebo (18341).
• Inflammatory bowel disease (IBD). It is unclear if oral or rectal N-acetyl glucosamine improves symptoms of IBD in children. Details: A very small clinical study in children ages 8-17 years with Crohn disease or ulcerative colitis that were unresponsive to conventional treatment suggests that oral or rectal N-acetyl glucosamine 1.5-2 grams in 10 mL water twice daily for 6 weeks might decrease symptoms of IBD when compared with baseline (10234). The validity of this finding is limited by a lack of control group.
• Interstitial cystitis. Oral glucosamine sulfate has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: An open-label clinical study in patients with interstitial cystitis shows that taking a specific product (CystoProtek, Tischon Corporation) containing glucosamine sulfate 120 mg, sodium hyaluronate 10 mg, chondroitin sulfate 150 mg, quercetin 150 mg, and rutin 20 mg per capsule, as two capsules twice daily for 12 months, reduces symptom severity by up to 52% when compared with baseline (42391). The validity of this finding is limited by a lack of control group.
• Joint pain. Oral glucosamine has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with joint pain shows that taking capsules of a specific combination product (Instaflex Joint Support, Direct Digital) containing glucosamine sulfate 1500 mg, methylsulfonylmethane 500 mg, white willow bark extract 250 mg, ginger root concentrate 50 mg, Boswellia serrata extract 125 mg, turmeric root extract 50 mg, cayenne 40 m H.U. 50 mg, and hyaluronic acid 4 mg, daily in three divided doses for 8 weeks, reduces joint pain severity by 37% compared to only 16% with placebo. However, the specific combination product does not appear to improve joint stiffness or function compared with placebo (89560).
• Kashin-Beck Disease. It is unclear if oral glucosamine hydrochloride improves Kashin-Beck Disease symptoms such as pain. Details: A small clinical study in Chinese adults with Kashin-Beck Disease shows that taking glucosamine hydrochloride 480 mg three times daily along with chondroitin sulfate 600 mg twice daily for 6 months decreases pain scores by at least 20% to 50% in more patients when compared with placebo. Taking glucosamine alone had a non-significant trend toward pain reduction in these patients (42516). An open-label study in Chinese adults with Kashin-Beck Disease shows that taking glucosamine hydrochloride 750 mg twice daily for 6 weeks seems to be no different for improving pain and physical function when compared with taking to diclofenac 50 mg twice daily or naproxen 300 mg twice daily (18339). The validity of this finding is limited by a lack of blinding.
• Kidney stones (nephrolithiasis). Oral glucosamine might reduce the risk of developing kidney stones. Details: A large observational study in adults without kidney stones suggests that regularly taking glucosamine is associated with a 28% lower risk of new-onset kidney stones in people with a total sedentary time under 3.5 hours daily. This association follows a dose-dependent relationship. However, regular glucosamine use does not seem to reduce the risk of new-onset kidney stones in people with total sedentary time exceeding 3.5 hours daily (112451).
• Knee pain. Small clinical studies suggest that oral glucosamine hydrochloride might improve exercise-induced knee pain and chronic knee pain. However, it is unclear if glucosamine sulfate, N-acetyl glucosamine, or lower doses of glucosamine hydrochloride are beneficial in these patients. Details: A small clinical study in athletes following an acute knee injury shows that taking glucosamine sulfate 500 mg three times daily for 28 days does not improve pain but might modestly improve mobility when compared with placebo (20103). Glucosamine has also been evaluated for chronic knee pain. A small clinical study in patients with chronic knee pain of unclear origin shows that taking glucosamine hydrochloride 2000 mg daily for 12 weeks might modestly improve pain when compared with placebo (10312). However, lower doses of glucosamine hydrochloride and N-acetyl glucosamine used in combination with other ingredients have not demonstrated benefit for chronic knee pain. A small clinical trial in Japanese adults over 40 with knee pain shows that taking a combination supplement with glucosamine hydrochloride and other ingredients for 16 weeks does not improve pain, function, or walking speed when compared with placebo. The combination supplement provided glucosamine hydrochloride 1200 mg, chondroitin sulfate 60 mg, type II collagen peptides 45 mg, quercetin glycosides 90 mg, imidazole peptides 10 mg, and vitamin D 200 IU daily (95784). Another small clinical study in Japanese patients over 50 years of age with chronic knee pain shows that taking a specific supplement (Walker's Glucosamine, Kyowa) containing N-acetyl glucosamine 100 mg and chondroitin sulfate 180 mg daily for 24 weeks does not reduce pain or improve knee function when compared with placebo (95795).
• Multiple sclerosis (MS). It is unclear if oral glucosamine sulfate is beneficial in patients with MS. Details: A small clinical study in patients with MS shows that taking glucosamine sulfate 1000 mg once daily for 6 months modestly reduces relapse when compared to baseline, but not when compared with placebo (20104).
• Overall mortality. It is unclear if oral glucosamine reduces overall mortality. Details: An observational study in the United States has found that regular use of oral glucosamine, with or without chondroitin, for an average of 8 years is associated with a 30% lower risk of mortality when compared with no glucosamine use. However, when adjusted for covariates such as age, body-mass index, and comorbidities, there was no difference in overall mortality (110626). In contrast, a cross-sectional observational study has found that using oral glucosamine and chondroitin for at least one year is associated with 27% reduced incidence of overall mortality and 58% reduced incidence of cardiovascular mortality when compared with not using these supplements (104445). This study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine and chondroitin use also reported overall healthier lifestyle habits than those that were not taking glucosamine and chondroitin. Although this study attempted to control for these differences, higher quality, prospective research is needed to clarify the relationship, if any, with overall mortality. Of note, some researchers have called into question the results from observational research linking glucosamine use to a lower rate of overall mortality, claiming that these studies suffer from a high risk of selection bias (109646).
• Postoperative recovery. It is unclear if oral glucosamine sulfate improves recovery after surgery. Details: A small clinical study in male athletes who have undergone anterior cruciate ligament (ACL) reconstruction shows that taking glucosamine sulfate (Solgar Inc.) 1000 mg daily for 8 weeks does not improve rehabilitation outcomes such as functional ability, pain, and muscular performance when compared with placebo (95584).
• Rheumatoid arthritis (RA). It is unclear if oral glucosamine hydrochloride is beneficial in patients with RA. Details: A small clinical study in patients with RA shows that taking glucosamine hydrochloride tablets (Rohto Pharmaceutical Co.) 500 mg three times daily by mouth for 12 weeks reduces pain, but not the number of painful or swollen joints, when compared with placebo (17407).
• Stroke. It is unclear if oral glucosamine is beneficial for reducing stroke risk. Details: An observational cohort study of adults in the United Kingdom found that taking glucosamine is associated with a modest 9% reduced risk for overall stroke; however, sub-analyses show that glucosamine use is not associated with a reduced risk for fatal or non-fatal stroke, hemorrhagic stroke, or ischemic stroke (99682). This study did not clarify the form of glucosamine used, or the dose, frequency, or duration of use. Furthermore, the adults that reported glucosamine use also reported overall healthier lifestyle habits than those that were not taking glucosamine. A case-control study in Spanish patients found that glucosamine use is associated with 45% lower odds of ischemic stroke when compared with non-use; however, the benefit was only observed in patients taking glucosamine for 1 year or less (109643). This study did not clarify the form of glucosamine used or the dose or frequency of use. Furthermore, patients in the control group were generally healthier and less likely to have a history of cardiovascular disease, diabetes, or hyperlipidemia. Although both studies attempted to control for differences between patient populations, higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and stroke risk.
• Temporomandibular disorders (TMD). It is unclear if oral glucosamine sulfate is beneficial in patients with temporomandibular joint osteoarthritis. Details: A small and low-quality clinical study in patients with temporomandibular joint osteoarthritis shows that taking glucosamine sulfate 500 mg three times daily for 90 days seems to be no different than taking ibuprofen 400 mg three times daily for relieving pain and improving functional abilities such as chewing, yawning, talking, and laughing (3714). However, another small clinical study in patients with the same condition shows that taking glucosamine sulfate 1200 mg daily for 6 weeks does not improve pain or jaw opening capacity when compared with placebo (20105). Glucosamine sulfate has also been evaluated in combination with chondroitin for this condition. A meta-analysis of two small clinical studies in patients with TMD shows that taking glucosamine sulfate 1500 mg and chondroitin sulfate 1200 mg daily for 2 months does not reduce pain or increase maximum mouth opening when compared with tramadol 50-100 mg daily (109647). Another small clinical trial in children aged 10-13 years with class II malocclusion shows that application of a specific combination gel product containing glucosamine, chondroitin, and essential oils (Jointace Gel, Vitabiotics) with an expander device, twice daily for 3 months does not improve temporomandibular space measures or pain or tension scores, when compared with placebo (110629).
• Wound healing. Although there is interest in using topical glucosamine for wound healing, there is insufficient reliable information about the clinical effects of glucosamine for this condition. More evidence is needed to rate glucosamine for these uses.

(Read more about GLUCOSAMINE)

POSSIBLY EFFECTIVE

• Osteoarthritis. Oral PEA seems to reduce pain and improve function in patients with osteoarthritis. Details: Clinical research in patients with osteoarthritis shows that taking PEA (Levagen, Gencor Pacific) 300 mg or 600 mg daily in two divided doses for 8 weeks modestly improves function and reduces pain, stiffness, and the need for rescue analgesics when compared with placebo. The worst reported pain from the day prior was reduced by 40% to 50% in patients taking PEA, compared with no improvement in those taking placebo. Also, the number of patients reporting no pain in the previous 24 hours was more than doubled in those taking PEA when compared with placebo (106274).
• Pain (chronic). Oral PEA seems to reduce pain in patients with chronic pain due to various causes. Details: A meta-analysis of the available clinical research, as well as one observational study, shows that taking micronized or ultramicronized PEA (Normast, Epitech Group) 300-1200 mg daily for up to 60 days reduces pain in people with chronic pain due to various causes, regardless of the use of other analgesics. The meta-analysis estimated a five-fold reduction in pain every two weeks in patients using PEA when compared to control. Estimates also suggest that pain reduction to a score of less than or equal to 3 is approximately twice as likely to occur in patients using PEA when compared to control (93314,93320). A more recent meta-analysis of small clinical studies in patients with pain of various etiologies taking PEA 300-1200 mg for 10-180 days did not find any further pain reduction with the use of higher doses or longer durations. There was also no difference in pain reduction when compared with either a placebo control or a non-placebo control (101327). The validity of these findings is limited by the variability of the studies in the analysis and the lack of differentiation between patients with neuropathic and non-neuropathic pain.

POSSIBLY INEFFECTIVE

• Spinal cord injury. Oral PEA does not seem to reduce pain or spasticity associated with spinal cord injury. Details: Clinical research shows that taking ultramicronized PEA (Normast, Epitech Group SpA) 600 mg sublingually twice daily for 12 weeks as add-on pain therapy does not reduce neuropathic pain, spasticity, or insomnia in patients with pain and spasticity associated with spinal cord injury when compared with using conventional pain treatments (93370).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if oral PEA is beneficial for ALS. Details: Preliminary clinical research in adults with ALS shows that taking ultramicronized PEA 600 mg twice daily for 6 months, in addition to riluzole 50 mg, slows the decline of pulmonary function when compared with a control group taking riluzole alone. Taking PEA also attenuates the reduction in forced vital capacity, with a 4% decrease in the treatment group compared to a 15% decrease in the control group (93369).
• Atopic dermatitis (eczema). Topical PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in patients with atopic dermatitis shows that using an emollient containing PEA 0.3% and N-acetylethanolamine 0.21% (Stiefel Laboratories Ltd) twice daily for 28 days modestly improves skin hydration, scaling, dryness, and itching when compared with a control emollient. There was no effect on skin redness or integrity (106271).
• Autism spectrum disorder. It is unclear if oral PEA is beneficial for autism. Details: A small clinical study in children aged 4-12 years with autism and moderate to severe irritability shows that taking PEA 600 mg twice daily for 10 weeks as an adjunct to treatment with risperidone improves irritability and hyperactivity, but does not seem to affect lethargy/social withdrawal, inappropriate speech, or stereotypic behavior, when compared with placebo and risperidone (101338).
• Cannabis use disorder. Although there is interest in using oral PEA for cannabis withdrawal, there is insufficient reliable information about the clinical effects of PEA for this condition.
• Carpal tunnel syndrome. It is unclear if oral PEA is beneficial for carpal tunnel syndrome. Details: Preliminary clinical research in patients with moderate severity carpal tunnel syndrome shows that taking PEA 600 or 1200 mg daily in divided doses for 30 days reduces or delays discomfort when compared to no treatment (93377). The validity of these findings is limited by the lack of an adequate comparator group. Another small preliminary clinical trial in patients with moderate to severe carpal tunnel syndrome shows that taking ultra-micronized PEA (Normast, Epitech Group S.p.A) 1200 mg daily prior to carpal tunnel surgery improves sleep disturbance and pain when compared with control. Two 600 mg sachets of the product were used daily for 10 days, followed by two 600 mg tablets daily for 50 days. The treatment regimen was then continued for another 90 days, but there was no difference between groups with regard to sleep and pain outcomes during this period (101333). PEA might not work as well in patients with milder carpal tunnel syndrome. A clinical study in patients with low to moderate severity carpal tunnel syndrome shows that taking PEA 300 mg twice daily for 60 days does not improve symptoms when compared with placebo (101334).
• Chronic kidney disease (CKD). Although there is interest in using oral PEA for CKD, there is insufficient reliable information about the clinical effects of PEA for this condition.
• Chronic prostatitis and chronic pelvic pain syndrome (CP/CPPS). Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small preliminary clinical study in patients with CP/CPPS shows that taking a specific combination product containing PEA 300 mg with alpha-lipoic acid 300 mg (Peanase) daily for 12 weeks improves lower urinary tract symptoms, pain, and quality of life, but does not improve erectile function, when compared with taking saw palmetto 320 mg (101336). It is not clear if these effects are due to PEA, other ingredients, or the combination.
• Circadian rhythm sleep disorders. It is unclear if oral PEA is beneficial in patients with disturbed sleep patterns. Details: A clinical study in healthy adults with disturbed sleep patterns shows that taking a specific formulation of oral PEA (Levagen+) 350 mg nightly, one hour prior to sleep, for 8 weeks does not improve the quality of sleep when compared with placebo. However, treatment with PEA shortens the time needed to fall asleep at weeks 4 and 8 when compared with placebo (107807). This study may have been inadequately powered to detect a difference between groups.
• Cognitive impairment. Although there is interest in using oral PEA for cognitive impairment, there is insufficient reliable information about the clinical effects of PEA for this condition.
• Complex regional pain syndrome. Although there is interest in using topical PEA for complex regional pain syndrome, there is insufficient reliable information about the clinical effects of PEA for this condition.
• Coronavirus disease 2019 (COVID-19). It is unclear if oral PEA is beneficial for recovery of smell following COVID-19 infection. Details: COVID-19 infection has been associated with persistent smell or taste disorder. In patients with olfactory impairment lasting at least 90 days after a confirmed negative COVID-19 test, a small preliminary clinical trial shows that taking PEA 700 mg plus luteolin 70 mg (Glialia, Epitech pharmaceutical) daily for 30 days in combination with olfactory rehabilitation modestly improves olfactory recovery, based on threshold, discrimination, and identification, when compared with olfactory rehabilitation alone. However, patients randomized to PEA plus luteolin had worse olfactory status at baseline and had experienced olfactory impairment for about twice the duration as those in the control group. These baseline differences may have confounded any findings (106270).
• Depression. It is unclear if oral PEA is beneficial for depression when used in combination with citalopram. Details: A small clinical trial in patients with major depressive disorder shows that, in addition to citalopram, taking ultra-micronized PEA 600 mg twice daily for 6 weeks results in at least a 50% improvement on the Hamilton Depression Rating Scale (HAM-D) in all patients, compared to about 75% of patients in the group receiving placebo and citalopram. However, there was no between-group difference in complete remission rates (101335).
• Diabetic neuropathy. It is unclear if oral PEA is beneficial for diabetic neuropathy. Details: Preliminary clinical research in adults with diabetic neuropathy shows that taking a specific type of micronized PEA (Normast, Epitech Group srl) 300 mg twice daily for 60 days reduces neuropathic pain when compared with baseline (93335). The validity of this finding is limited by the lack of a comparator group.
• Dry eye. It is unclear if eye drops containing PEA are beneficial for dry eye. Details: Observational research in patients with glaucoma and dry eye has found that applying specific PEA eye drops (Defluxaa), one drop in each eye twice daily for 30 days, is linked to improved tear stability and tear production (101332).
• Dry skin. It is unclear if topical PEA is beneficial for dry skin. Details: Preliminary clinical research in patients with pruritus related to dry skin shows that applying a lotion containing PEA (Physiogel Calming Relief) twice daily for 14 days does not reduce itchiness, roughness, or scaling when compared with applying the vehicle alone (106272).
• Dysmenorrhea. Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Clinical research in adolescents and young adults with primary dysmenorrhea shows that taking a combination of PEA 400 mg plus trans-polydatin 40 mg daily for 10 days, starting on the 24th day of the cycle, modestly reduces pelvic pain when compared with placebo. Also, approximately 98% of patients taking PEA had some pain reduction, compared with 56% of those taking placebo (106273).
• Endometriosis. Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A meta-analysis of clinical and observational research in patients with endometriosis-related pain shows that taking micronized PEA 400 mg and trans-polydatin 40 mg twice daily for 3 months moderately improves pelvic pain and dysmenorrhea and modestly improves pain with intercourse when compared with placebo (101337). However, taking the same specific combination of PEA 400 mg plus polydatin 40 mg (Pelvilen, Epitech Group Srl) daily for 3 months was not as effective as taking celecoxib 200 mg twice daily for 7 days. Satisfaction with treatment is comparable between PEA and celecoxib (101407). Limited research has also assessed PEA in combination with alpha-lipoic acid. Preliminary clinical research shows that taking a combination of PEA 300 mg and alpha-lipoic acid 300 mg twice daily for 6-9 months reduces endometriosis-associated pelvic pain and improves quality of life and sexual function when compared to baseline (93379). The validity of this finding is limited by the lack of a comparator group.
• Exercise-induced muscle damage. It is unclear if oral PEA is beneficial for the prevention or treatment of exercise-induced muscle damage. Details: A small clinical study in young males shows that taking a drink containing PEA 150 mg (as Levagen+) plus maltodextrin 832.5 mg before, immediately after, and 3 hours, 24 hours, and 48 hours after an exercise session designed to cause muscle damage modestly reduces myoglobin levels, a marker of muscle damage, in the 3-hour post-exercise period when compared with taking maltodextrin 1 gram. However, there were no effects on levels of creatine kinase or inflammatory cytokines over 72 hours (106267).
• Exercise-induced muscle soreness. It is unclear if oral PEA is beneficial for the prevention or treatment of exercise-induced muscle soreness. Details: A small clinical study in young males shows that taking a drink containing PEA 150 mg (as Levagen+) plus maltodextrin 832.5 mg before, immediately after, and 3 hours, 24 hours, and 48 hours after an exercise session designed to cause muscle soreness does not reduce muscle soreness in the 72-hour post-exercise period when compared with taking maltodextrin 1 gram (106267).
• Fibromyalgia. It is unclear if oral PEA is beneficial for fibromyalgia. Details: Retrospective and prospective observational research in patients with fibromyalgia who are taking duloxetine and pregabalin shows that taking micronized or ultramicronized PEA (PEA-m or PEA-um, Epitech Group) 600-1200 mg daily for 3 months reduces pain and tender points when compared with duloxetine and pregabalin alone (93338). The validity of these findings is limited by poor study design and the lack of a placebo control.
• Glaucoma. Taking oral PEA seems to have a small beneficial effect on intraocular pressure. However, it is unclear if oral PEA is beneficial for glaucoma. Details: In patients with normal-tension glaucoma, preliminary clinical research shows that taking ultramicronized PEA 600 mg in divided doses for 6 months reduces intraocular pressure by 3.3 mmHg and improves visual field indices without impacting visual acuity when compared to baseline (93378). Other preliminary clinical research in patients with stable open-angle or normal tension glaucoma already using standard topical therapy shows that taking PEA (Visimast) 600 mg daily for 4 months modestly improves the function of retinal ganglion cells, intraocular pressure, and quality of life when compared with not taking PEA. However, in this study there was no effect on the visual field (106268). PEA has also been evaluated for the general reduction of intraocular pressure. In patients undergoing bilateral laser iridotomy for the prevention of primary closed-angle glaucoma, a small clinical study shows that taking a specific PEA product (Visimast, Epitech Group Srl) 300 mg twice daily for 15 days prior to surgery prevents a rise in intraocular pressure within 2 hours of surgery when compared with placebo (93323). In patients with ocular hypertension but without other symptoms of glaucoma, preliminary clinical research shows that taking PEA 300 mg twice daily for 90 days reduces levels of intraocular pressure by approximately 3% when compared to baseline (93326). The validity of these findings is limited by the lack of a comparator group.
• Inflammatory bowel disease (IBD). Although there is interest in using oral PEA for IBD, including Crohn disease and ulcerative colitis, there is insufficient reliable information about the clinical effects of PEA for these conditions.
• Interstitial cystitis. Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in males and females with interstitial cystitis and chronic bladder pain shows that taking a product containing micronized PEA 400 mg plus polydatin 40 mg (Pelvilen Forte, Epitech Group SpA) twice daily for 3 months, and then once daily for an additional 3 months, modestly reduces pain intensity, urgency, and frequency when compared with baseline. The pain reduction was maintained for at least an additional 2 months (106269). The validity of these findings is limited by the lack of a comparator group.
• Irritable bowel syndrome (IBS). Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with IBS shows that taking PEA 200 mg and polydatin 20 mg (EP1844784, Epitech group Srl) twice daily for 12 weeks reduces abdominal pain severity but does not affect other gastrointestinal symptoms when compared with placebo (101331). It is not clear if these effects are due to PEA, other ingredients, or the combination.
• Migraine headache. It is unclear if oral PEA is beneficial for reducing the frequency and severity of migraines in children. Details: Preliminary clinical research in children and adolescents aged 5-17 years with migraine without aura shows that taking ultra-micronized PEA 300 mg twice daily for 3 months reduces the frequency of migraine attacks by at least 50% in about 64% of patients when compared with baseline. The intensity of migraine attacks was reduced by approximately 30%, with an 80% reduction in the number of patients experiencing a severe migraine attack (106266). The validity of these findings is limited by the lack of a comparator group.
• Multiple sclerosis (MS). It is unclear if oral PEA is beneficial for MS. Details: Anecdotal evidence from case reports has suggested that PEA can reduce MS-related pain (93319,93321). Preliminary clinical research in patients with relapsing-remitting MS being treated with subcutaneous interferon-beta1a shows that taking ultra-micronized PEA (Normast, Epitech Group SpA) 600 mg daily for 12 months improves some, but not all, symptoms of MS, as well as adverse effects from interferon treatment. However, taking PEA does not seem to improve physical or emotional well-being or overall quality of life (93368).
• Neuropathic pain. It is unclear if oral PEA is beneficial for improving neuropathic pain. Details: Small, low-quality clinical studies and case series suggest that taking PEA 600-1200 mg daily in divided doses reduces neuropathic pain from various causes, including chemotherapy and trauma. Pain reduction has been reported to occur even if patients are using other treatments or receiving acupuncture (93333,93336,93376). The validity of these findings is limited by small study size, poor study design, and the lack of a comparator group.
• Obesity. Although there is interest in using oral PEA for weight loss, there is insufficient reliable information about the clinical effects of PEA for this use.
• Parkinson disease. It is unclear if oral PEA is beneficial for patients with Parkinson disease using levodopa. Details: Observational research in patients with Parkinson disease using levodopa found that taking a specific ultra-micronized PEA product (Normast, Epitech Group SpA) 600 mg twice daily for 3 months, followed by 600 mg once daily for up to one year, is associated with improved symptoms when compared to baseline, such as mood, sleep disturbances, and tremor, and improved activities such as getting out of bed and walking (101328). The validity of these findings is limited by the observational nature of the study and the lack of a comparator group.
• Postoperative pain. It is unclear if oral PEA is beneficial for reducing postoperative pain. Details: Preliminary clinical research in adults undergoing impacted third molar extraction shows that taking a specific type of micronized PEA (Normast, Epitech Group SpA) 300 mg twice daily for 15 days reduces postoperative pain when compared with a control group. PEA reduces pain by 36% and 33% at 3 and 7 days, respectively, when compared with control (93322).
• Prurigo nodularis. Topical PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in elderly individuals with chronic pruritus or prurigo nodularis shows that topical application with a cream containing 10% omental lipids and 'anti-itching' agents, including PEA, twice daily for 4 weeks reduces itching severity by 86% when compared with baseline. Skin barrier function was also improved. Other 'anti-itching agents' included polidocanol and stimutex made up of spent grain wax, shea extract, and Argania spinosa kernel oil (106275). The validity of these findings is limited by the lack of a comparator group.
• Respiratory tract infections. It is unclear if oral PEA is beneficial for preventing respiratory tract infections. Details: Some low-quality, clinical studies in adults and children shows that taking a specific type of PEA (Impulsin) up to 1800 mg daily in divided doses for at least 12 days reduces the risk of developing an acute respiratory infection by 32% to 59% (93372,101412). Retrospective, observational research in children with recurrent respiratory infections shows taking a specific product (Sinerga) containing PEA, bovine colostrum, and phenylethylamine, as one sachet daily for 10-20 consecutive days each month for 4 months, reduces the need for antibiotics. The combination product reduced the need for antibiotic treatment to only 52% of children, compared to 95% of the children taking a probiotic extract (93337). It is not clear if these effects are due to PEA, other ingredients, or the combination.
• Sciatica. Small clinical studies suggest that oral PEA may be beneficial for reducing pain associated with sciatica. Details: Some small clinical studies in patients with sciatica shows that taking PEA 300 mg twice daily for 30 days in conjunction with standard treatment reduces pain and physical aspects of quality of life when compared with standard treatment alone (93374,93375). Some higher quality clinical research in adults with sciatica and low back pain also shows that taking a specific type of PEA (Normast, Epitech Group srl) 300 mg or 600 mg daily for 21 days reduces pain by 45% to 70% in patients with lumbosciatica, compared to a 30% reduction with placebo (101408,101409).
• Shigellosis. Although there is interest in using oral PEA for shigellosis, there is insufficient reliable information about the clinical effects of PEA for this use.
• Stroke. Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: Preliminary clinical research in stabilized, conventionally-treated adults undergoing rehabilitative treatment for a recent stroke shows that taking a specific product (Glialia, Epitech Group SpA) containing ultra-micronized PEA 700 mg and luteolin 70 mg twice daily sublingually for 60 days improves spasticity, pain, and activities of daily living when compared to baseline (93339). The validity of these findings is limited by the lack of a comparator group.
• Temporomandibular disorders (TMD). It is unclear if oral PEA is beneficial for TMD. Details: Preliminary clinical research shows that taking PEA 600-900 mg in divided doses for 14 days improves pain associated with temporomandibular arthritis by 89%, compared to only 46% in patients taking ibuprofen 600 mg three times daily for 14 days. PEA also increased mouth opening by 11.5%, compared to an increase of 5.5% with ibuprofen (93373).
• Tourette syndrome. Although there is interest in using oral PEA for Tourette syndrome, there is insufficient reliable information about the clinical effects of PEA for this use.
• Vulvar pain. Oral PEA has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical study in patients with vestibulodynia shows that taking PEA 400 mg plus polydatin 40 mg daily, in conjunction with intravaginal transcutaneous electrical nerve stimulation (TENS) therapy, does not reduce pain more than the use of TENS therapy and placebo (93327). More evidence is needed to rate PEA for these uses.

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LIKELY SAFE ...when glucosamine sulfate is used orally and appropriately. Glucosamine sulfate has been used safely in multiple clinical trials at a dose of 1000-1500 mg daily for 4 weeks to 3 years (2604,7026,8942,11340,12461)(14305,16717,89558,89567,94380,94382,95785).

POSSIBLY SAFE ...when glucosamine hydrochloride is used orally and appropriately. Glucosamine hydrochloride has been used with apparent safety at a dose of 1400-1600 mg daily for up to 2 years (4237,13579,14809,18344,42477,89516,89519,95784). Glucosamine hydrochloride 2 grams daily has also been used with apparent safety for up to 3 weeks (103281). ...when N-acetyl glucosamine is used orally and appropriately. N-acetyl glucosamine 100 mg daily has been used with apparent safety for up to 24 weeks (95795). ...when N-acetyl glucosamine is applied topically and appropriately. A 2% N-acetyl glucosamine cream has been safely used for up to 10 weeks (92721). ...when N-acetyl glucosamine is used rectally and appropriately. N-acetyl glucosamine 3-4 grams daily in 2 divided doses has been safely used (10234). ...when glucosamine sulfate is used intramuscularly and appropriately, short-term. Intramuscular glucosamine sulfate seems to be well tolerated when given twice weekly for up to 6 weeks (2605).

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

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POSSIBLY SAFE ...when used orally and appropriately, short-term. PEA has been used with apparent safety in doses of up to 1400 mg daily for up to 3 months (93314,93326,93327,93333,93335,93338,93339,93369,93373,101333)(101335,106269,106274). ...when used topically and appropriately, short-term. An emollient containing PEA 0.3% and N-acetylethanolamine 0.21% (Stiefel Laboratories Ltd) had been used with apparent safety twice daily for up to 28 days (106271). There is insufficient reliable information available about the safety of PEA when applied topically or when used orally, long-term.

CHILDREN:
. ..when used orally and appropriately, short-term. PEA 300-600 mg twice daily for 10-12 weeks has been used with apparent safety in children 4-17 years old (101338,106266).

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

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ACETAMINOPHEN (Tylenol, others) Interaction Rating = Minor Be watchful with this combination. Severity = Insignificant •  Occurrence = Possible •  Level of Evidence = B Acetaminophen might interfere with the activity of glucosamine sulfate by interacting with the sulfate portion.  Details Anecdotal reports suggest that adding glucosamine to an acetaminophen regimen might decrease pain control in patients with osteoarthritis (14806). Some research suggests that the sulfate portion of glucosamine sulfate might contribute to its effect in osteoarthritis. Since acetaminophen metabolism requires sulfur and reduces serum sulfate concentrations, acetaminophen could theoretically interfere with the action of glucosamine sulfate. Conversely, the administration of sulfate could theoretically decrease the effectiveness of acetaminophen in sulfate-deficient people by increasing its clearance (10313).

ANTIDIABETES DRUGS Interaction Rating = Minor Be watchful with this combination. Severity = Moderate •  Occurrence = Unlikely •  Level of Evidence = B Despite initial concerns, it is unlikely that glucosamine will interfere with the effects of antidiabetes drugs.  Details In vitro and animal research has suggested that glucosamine might increase insulin resistance or decrease insulin production (371,372,3406,18342,18343). This has raised concerns that taking glucosamine might worsen diabetes and decrease the effectiveness of diabetes drugs. However, clinical research suggests that glucosamine does not have adverse effects on blood glucose or glycated hemoglobin (HbA1C) in healthy, obese, or type 2 diabetes patients (7026,7075,8942,10311,10317,15111).

TOPOISOMERASE II INHIBITORS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically glucosamine may induce resistance to topoisomerase II inhibitors.  Details In vitro research suggests that glucosamine might induce resistance to etoposide (VP16, VePesid) and doxorubicin (Adriamycin) by reducing inhibition of topoisomerase II, an enzyme required for DNA replication in tumor cells (7639). This effect has not been reported in humans.

WARFARIN (Coumadin) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = D Glucosamine might increase the anticoagulant effects of warfarin and increase the risk of bruising and bleeding.  Details In two individual case reports, glucosamine/chondroitin combinations were associated with a significant increase in international normalized ratio (INR) in patients previously stabilized on warfarin (11389,16130). In one case, the increase in INR occurred only after tripling the dose of a glucosamine/chondroitin supplement from 500 mg/400 mg daily to 1500/1200 mg daily (16130). Additionally, 20 voluntary case reports to the U.S. Food & Drug Administration (FDA) have linked glucosamine plus chondroitin with increased INR, bruising, and bleeding in patients who were also taking warfarin (16130). There have also been 20 additional case reports to the World Health Organization (WHO) that link glucosamine alone to increased INR in patients taking warfarin (16131). The mechanism of this interaction is unclear. Glucosamine is a small component of heparin, but is not thought to have anticoagulant activity; however, animal research suggests that it might have antiplatelet activity (16131).

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General ...Orally, all forms of glucosamine seem to be well tolerated. Topically and rectally, N-acetyl glucosamine also seems to be well tolerated. Intramuscularly, glucosamine sulfate seems to be well tolerated. However, a thorough evaluation of safety outcomes has not been conducted for non-oral routes of administration.
Most Common Adverse Effects:
Orally: Bloating, constipation, cramps, diarrhea, heartburn, nausea.
Serious Adverse Effects (Rare):
Orally: There have been rare reports of severe allergic reactions and hepatotoxicity.

Cardiovascular ...One case of mesenteric occlusion in a clinical trial was considered possibly related to use of oral glucosamine hydrochloride and chondroitin sulfate (89520).
Some observational research has found that glucosamine use in patients with osteoarthritis is associated with a higher risk of cardiovascular disease (CVD) events when compared with non-use (109642). However, glucosamine users tended to be older, have multiple comorbidities, and be on antihyperlipidemic or antiplatelet therapy. Furthermore, other observational research in healthy adults has found that glucosamine use is associated with a reduced risk of fatal and non-fatal CVD events (99682). Higher quality, prospective research is needed to clarify the relationship, if any, between glucosamine and CVD risk.

Dermatologic ...Orally, glucosamine might cause skin reactions, including itching, rash, and erythema (2608,20084,89567,110628). Also, fingernail and toenail toughening, with an increased rate of growth, has been reported (89572). Topically, N-acetyl glucosamine 2% with niacinamide 4% cream might cause rare skin reactions (92721). Photosensitization that was reproducible with re-challenge was reported in a case report of an individual using glucosamine (form unknown) and chondroitin (10408).

Endocrine ...Orally, glucosamine does not seem to impact blood glucose. Preliminary research and anecdotal reports have found that various forms of glucosamine might increase insulin resistance or decrease insulin production, increasing fasting plasma glucose levels (22,371,372,1203,3406,5059,7637,14810). This has raised concerns that taking glucosamine sulfate might worsen diabetes and decrease the effectiveness of diabetes drugs. However, clinical research suggests that various forms of glucosamine do not have adverse effects on blood glucose or glycated hemoglobin (HbA1C) in healthy, obese, patients with type 2 diabetes or impaired glucose tolerance (7026,7075,7638,8942,10311,10317,12107,14808,15111,89563).

Gastrointestinal ...Orally, glucosamine has been associated with gastrointestinal problems, including epigastric and abdominal pain, cramps, heartburn, diarrhea, nausea, dyspepsia, vomiting, constipation, and flatulence (1520,2608,16717,20084,20104,20105,89561,89562,89567,89568)(108897,110628,111647). In older persons, use of glucosamine sulfate is associated with oral dryness (89564). In a clinical trial, a case of Helicobacter pylori gastritis was considered probably related to the use of glucosamine hydrochloride (89516).

Hepatic ...Although relatively uncommon, combinations of glucosamine and chondroitin sulfate have been associated with acute liver injury that mimics autoimmune hepatitis. Of 151 patients at an outpatient clinic for liver diseases, 23 acknowledged use of products containing glucosamine (form unspecified) and/or chondroitin. However, only 2 cases had an apparent relationship between transaminase elevation and the use of recommended doses of glucosamine and chondroitin sulfate. Aminotransferase levels, which were increased by four- to seven-fold, returned to normal following discontinuation of treatment (89515). In another case, a 65-year-old male presented to the hospital with signs and symptoms of drug-induced autoimmune hepatitis. The patient had used Condrosulf, containing chondroitin sulfate, for two years, followed by Vita Mobility Complex, containing chondroitin sulfate and glucosamine sulfate, for 8 weeks. The patient required maintenance treatment with azathioprine to remain in remission (89518). A case of acute cholestatic hepatitis due to Glucosamine Forte, which contains glucosamine hydrochloride, chondroitin sulfate, Devil's claw, and shark cartilage, has been reported (89522). It is unclear whether these adverse events were related to glucosamine, other ingredients, or the combination.

Immunologic ...There is some concern that glucosamine products might cause allergic reactions in sensitive individuals. One review of glucosamine-related adverse events in Australia found that 72% of all reports involved hypersensitivity reactions. Of these reactions, 35% were mild, including pruritis, urticaria, and lip edema, 49% were moderate, including dyspnea, and 16% were severe, including gait disturbance, somnolence, and hypotension. Anaphylaxis was reported in 1.5% of cases (102115). Also, in one clinical trial, a single patient developed allergic dermatitis considered to be likely due to glucosamine hydrochloride (89516). Glucosamine is derived from the exoskeletons of shrimp, lobster, and crabs. However, it is unclear if these adverse reactions were due to a shellfish sensitivity or general atopy. Additionally, shellfish allergies are caused by IgE antibodies to antigens in the meat of shellfish, not to antigens in the exoskeleton. Regardless, it is possible that some glucosamine products might be contaminated by this allergen during production (102115).

Neurologic/CNS ...Orally, glucosamine has been reported to cause drowsiness and headache (2608,89561). Glucosamine plus chondroitin combination products that also contain manganese (e.g., CosaminDS) should always be taken according to product directions. When taken at doses slightly higher than the recommended dose, these products can sometimes supply greater than the tolerable upper limit (UL) for manganese which is 11 mg/day. Ingestion of more than 11 mg/day of manganese might cause significant central nervous system toxicity (7135).

Ocular/Otic ...In older persons, use of glucosamine sulfate has been associated with ocular dryness (89564). Increased intraocular pressure has occurred with glucosamine sulfate supplementation (89573,112460). Data from the FDA MedWatch adverse event reporting system shows that 0.21% of subjects taking glucosamine reported glaucoma, which is significantly greater than the 0.08% of subjects who reported glaucoma while using any other drug (112460).

Pulmonary/Respiratory ...Cases of asthma exacerbations associated with the use of glucosamine (form unknown)-chondroitin products have been reported (10002).

Renal ...Anecdotal reports have associated glucosamine with nephrotoxicity signals such as modestly elevated creatine phosphokinase and 1+ to 2+ proteinuria, but changes in kidney function have not been reported in long-term studies (7026,8942,10408,10409). It was also noted that effects may have been due to other concurrent medications or impurities in glucosamine-chondroitin products. Cases of acute interstitial nephritis induced by glucosamine (form unknown) have also been reported (89523).

Other ...There has been concern that glucosamine might increase the risk of metabolic disturbances resulting in increased cholesterol levels and blood pressure. However, glucosamine does not appear to increase the risk of these adverse effects. Taking glucosamine sulfate for up to 3 years does not significantly increase blood glucose or lipid levels, or cause any other disturbances in metabolism (7026,7075,8942,10311,10317).

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General ...Orally and topically, PEA seems to be generally well tolerated.
Most Common Adverse Effects:
Orally: Nausea.

Cardiovascular ...Orally, PEA has been reported to cause palpitations in one patient (93322).

Dermatologic ...Topically, applying a lotion containing PEA twice daily worsened pruritus and caused stinging, scaling, or reddening in 13% of patients with dry skin. However, these adverse effects did not occur more frequently than in patients applying the vehicle alone (106272).

Gastrointestinal ...Orally, PEA has been rarely reported to cause mild and transient gastrointestinal symptoms, such as nausea (93325,93327,106266).

Genitourinary ...Orally, PEA has been rarely reported to cause spotting when used in combination with polydatin. However, it is unclear whether this adverse effect is due to PEA, polydatin, or the combination (93325).

Neurologic/CNS ...Orally, PEA has been reported to cause drowsiness or a sensation of floating in one patient each (93322,106266).

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