Glucosamine : Dosing and Safety

by MedlinePlus

(Page 2 of 3)

Dosing

Standardization

Standardization involves measuring the amount of certain chemicals in products to try to make different preparations similar to each other. It is not always known if the chemicals being measured are the "active" ingredients. Glucosamine is not considered a drug in the United States and is therefore not required to be tested for quality by any agency prior to sale. Therefore, glucosamine preparations in the United States may vary in quality among different manufacturers and from batch to batch within the same manufacturer. In parts of Europe, glucosamine sulfate is available as a prescription drug of defined chemical nature. Most studies of glucosamine taken by mouth have used glucosamine sulfate, although different glucosamine salts are available, including glucosamine hydrochloride and glucosamine hydroiodide.

Adults (18 years and older)

Osteoarthritis: In most available studies, 500 milligrams of glucosamine sulfate has been used, taken by mouth as tablets or capsules three times daily, for 30 to 90 days. Once daily dosing as 1.5 grams (1500 milligrams) has also been used. Limited research has used 1500 milligrams daily as a crystalline powder for oral solution, or 500 milligrams of glucosamine hydrochloride three times daily. Dosing of 20 milligrams per kilogram of body weight daily has also been recommended in some publications. One study used a dose of 2000 milligrams per day for 12 weeks.

Other forms of glucosamine studied for osteoarthritis include: intra-articular (joint injections) of 400 milligrams of glucosamine sulfate daily for seven days, 400 milligrams of glucosamine sulfate intravenously (through the veins) daily for seven days, and muscular injections of 400 milligrams twice weekly. Another kind of glucosamine that has been used is a topical form in combination with chondroitin for a four-week period. Safety and effectiveness of these formulations are not clearly proven.

Glucosamine hydrochloride provides more glucosamine than glucosamine sulfate , although this difference likely does not matter when products are prepared to provide a total of 500 milligrams of glucosamine per tablet.

Children (younger than 18 years)

There is not enough scientific evidence to recommend the use of glucosamine in children. Preliminary research has been done using N-acetyl-glucosamine in a small number of children with inflammatory bowel disease, at a dose of 3 to 6 grams daily for an average of two and a half years.

Research in children has shown that there could be a relationship between the ingestion of MSM (methylsulfonylmethane) and autism; whether it is beneficial or harmful is unclear. MSM is often marketed with glucosamine as a dietary supplement and at this time should be avoided in children.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Since glucosamine can be made from the shells of shrimp, crab, and other shellfish, people with shellfish allergy or iodine hypersensitivity may have an allergic reaction to glucosamine products. A serious hypersensitivity reaction including throat swelling has been reported with glucosamine sulfate. However, a small pilot study of six patients with known systemic reaction to shellfish, showed no reaction when challenged with glucosamine. The authors conclude that this study, which indicated that glucosamine is probably safe for patients with shellfish allergy, needs to be confirmed by larger studies looking at different shellfish allergens and the consistency of glucosamine formulations. Hence, it seems that caution may still be warranted.

Side Effects and Warnings

In most human studies, glucosamine sulfate at a dose of 500 milligrams three times daily (tablets or capsules) has been well tolerated for 30 to 90 days. In a three-year study and several short-term trials, the number of adverse events in patients taking glucosamine was no different from placebo (sugar pill). There have been reports that in laboratory animals, doses as high as 5000 milligrams per kilogram taken by mouth, 3000 milligrams per kilogram injected into muscle, and 1500 milligrams per kilogram through the veins have not caused death.

Side effects may include upset stomach, drowsiness, insomnia, headache, skin reactions, sun sensitivity, and nail toughening. There are rare reports of abdominal pain, loss of appetite, vomiting, nausea, flatulence (gas), constipation, heartburn, and diarrhea. Based on several human cases, temporary increases in blood pressure and heart rate, as well as palpitations may occur with glucosamine/chondroitin products. Based on animal research, glucosamine theoretically may increase the risk for eye cataract formation.

It remains unclear if glucosamine alters blood sugar levels. Several human studies suggest no effects on blood sugar, while other research reports effects on insulin. Preliminary studies show no effect on mean hemoglobin A1c concentrations in patients with type 2 diabetes mellitus. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

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