**4. Adulteration of dietary supplements**

A final note is necessary regarding the adulteration of weight loss supplements with drug products and other chemical substances. This adulteration is often the underlying cause for the purported activity of a dietary supplement and can result in serious toxicity. The most commonly cited contaminant in weight loss supplements is sibutramine (Meridia®; see above), a weight loss supplement removed from the market in October 2010 for significant cardiac toxicities [462-466]. One U.S. FDA report cites 72 different herbal products containing adul‐ terants, 94.4% of which contained sibutramine as an additive [102]. Multiple products listed in the report were contaminated with phenolphthalein (11.1%) or the anti-seizure drug phenytoin (2.8%). Other reported contaminants (1.4%) included the experimental anti-obesity agent cetilistat, the recalled anti-obesity agent rimonabant (see above), the anti-obesity amphetamine stimulant drug fenproporex, the antidepressant fluoxetine, or the diuretics furosemide and bumetanide[103]. Phenophthalein was previously used as a laxative in overthe-counter products but was removed from the U.S. market in 1999 due to concerns of carcinogenicity and genotoxicity [467]. Another study investigating contamination of 20 different dietary supplements using 1H-NMR methods found contamination of 14 of the products (70%), with eight products containing sibutramine, five containing both sibutramine and phenolphthalein, and one formulation containing undeclared synephrine [468]. There have been other reports of contamination of weight loss supplements with the diuretic hydrochlorothiazide [462, 469]. Given that tainting of weight loss supplements is common, patients and health care professionals should be made aware of the risks associated with ingestion of herbal products, especially those with minimal evidence backing their claims of efficacy.
