Herbal Supplements: Precautions and Safe Use.

The Food and Drug Administration (FDA) classifies herbal preparations as food supplements. New herbal supplements and products are not governed by the strict FDA drug approval process and there is no premarket approval required. The FDA prohibits manufacturers and distributors from marketing adulterated or misbranded products but does not rigorously define safe practices. Scientific evidence related to herbal supplements is limited. Herbal supplements have been associated with adverse reactions and herbal-drug interactions. Information and precautions for 20 common herbal supplements, including St. John's wort, ginseng, echinacea, and ginkgo, are reviewed. Resources for consumers and health care professionals are highlighted.