Safety of Herbal Medicines

Although many medicinal herbs are relatively safe, some have significant toxicity. Herbs themselves can have unanticipated effects such as hepatotoxicity as seen with chaparral and germander. Ten of twenty patients with fulminant hepatic failure referred to a liver transplant service over a 21-month period were recent or active users of potentially hepatotoxic supplements. Ma-huang contains ephedrine and was sold as a component of many weight loss products and in a banned euphoriant called “herbal ecstasy.” Over 800 adverse events associated with Mahuang have been reported, including the widely publicized death of a US major league baseball player in 2003, causing the FDA to ban ephedra-containing products from the market. (See Ephedra in the specific herbs section for details.) Herbal products may also be intentionally adulterated with prescription drugs or contaminated with harmful substances such as pesticides or heavy metals. Prescription drugs such as prednisone, nonsteroidal anti-inflammatory drugs (NSAIDs), antibiotics, and testosterone have been detected in imported Chinese patent medicines. An estimated 15 million adults in 1997 took herbal medicines concurrently with prescription medications, creating a potential risk for adverse drug-herb or drug-supplement interactions. Patients taking St. John's wort along with the drugs indinavir or cyclosporine have lower blood levels of these prescription medicines. St. John's wort has the capacity to induce the cytochrome P450 system, which can lead to increased metabolism (ie, lower blood levels) of almost 50% of all prescription medicines that are processed by this system such as warfarin, theophylline, and birth control pills. Proving that a side effect experienced by a patient taking a dietary supplement is caused by that supplement is often difficult. Practitioners should take a detailed history from the patient and, if possible, obtain a sample of the product to facilitate further analysis if needed. All suspected adverse events should be reported to the FDA's Medwatch Program (http://www.fda.gov/medwatch), although it is estimated that fewer than 1% are actually reported.