Since the last Medical Letter article on glucosamine for osteoarthritis (vol.39, page 91, September 26, 1997), more data have become available. Glucosamine is available in US pharmacies and health food stores as sulfate, hydrochloride or n-acetyl salt.

The FDA recently advised health care professionals and consumers not to use a number of dietary supplements found to contain the phosphodiesterase-5 inhibitor sildenafil (Viagra) or an analog of the drug (www.fda.gov). Although the effects of sildenafil may be noticeable (in men), the presence of other, possibly more toxic adulterants in dietary supplements may be more difficult or impossible to detect.Other drugs previously found in dietary supplements have included lovastatin (Mevacor, and others), estrogen, alprazolam (Xanax, and others), indomethacin (Indocin, and others) and warfarin...

Probiotics are live, nonpathogenic microorganisms (usually bacteria or yeasts) marketed as dietary supplements. They have not been approved by the FDA for any indication. Since our last article on this subject, some new data have become available.

Dehydroepiandrosterone (DHEA), an endogenous adrenal steroid, is marketed as a dietary supplement in the US. It is widely promoted to reverse the effects of aging (loss of muscle, memory and libido) and has been used by athletes as a substitute for anabolic steroids. DHEA is banned by the International Olympic Committee, National Collegiate Athletic Association, National Football League and other sports organizations, but it was specifically exempted from becoming a controlled substance in the Anabolic Steroid Control Act of 2004.

PC Spes, a dietary supplement sold for "prostate health", is being used increasingly to treat prostate cancer.

S-adenosyl-methionine (SAM; SAMe; ademetionine; adomet), an endogenous compound synthesized from methionine and adenosine-triphosphate (ATP), has been marketed in stores and on the internet as a dietary supplement to promote "emotional well being."

Red yeast rice is a food product that has been used in Chinese cooking and medicine for centuries. It is available in the US in a capsule formulation and is often used by patients who want a "natural" product to lower cholesterol.

Patients may be asking about Airborne, a dietary supplement that is being heavily promoted for prevention and treatment of colds. It contains 7 herbal extracts, 3 vitamins, 2 amino acids, selenium, zinc and many other ingredients. Airborne Jr is available for children. There are some concerns. First, there is no conclusive evidence that this product or any of its ingredients prevents colds or shortens their duration. Second, the adult tablet contains 1 g of vitamin C, and the directions for use advise taking 1 tablet at the first sign of a cold and repeating the dose every 3 hours as...

Resveratrol is a phytochemical found in the skin of red grapes and in many other plants, including berries, plums and peanuts. As a constituent of red wine, it has been associated with cardioprotective effects. Dietary supplements containing resveratrol are now being widely promoted as antioxidants that can prevent agerelated diseases.

Extracts made from leaves of the ginkgo tree (Ginkgo biloba) are available in the uSA as deitary supplements, in France and Germany as licensed drugs and worldwide as herbal remedies for treatment of dementia and many other indications.