Herbal medicines today and the roots of modern pharmacology

The transformation of digitalis from a folk medicine, foxglove, to a modem drug, digoxin, illustrates principles of modern pharmacology that have help ed make drugs safer and more effective. Digitalis was improved because its preparation was standardized, first by bioassay and then by chemical method s; however, few of today's herbs are standardized by methods that can ensur e a consistent product and, hence, consistent safety and efficacy profiles. Many herbs have been evaluated in randomized, controlled trials, and sever al-St. John's wort and ginkgo, for example-are apparently effective. Yet, m any trials of herbs have limited value because of poor design, small sample s, and, above all, use of products of uncertain composition and consistency . The uncertain composition of many herbal products raises questions about their safety as does evidence indicating that herbs may have harmful intera ctions with prescription drugs. Such adverse effects of herbs are probably underreported. Meanwhile, systematic studies, such as those identifying adv erse reactions to drugs, are hindered because herbal preparations are not s tandardized-one: brand of St. John's wort, for example, will differ chemica lly from another-and, unlike for prescription drugs, there are no databases linking herb consumption to later medical problems. Since herbal medicines are regulated as dietary supplements, they are not subject to the premarke ting regulatory clearance required for drugs. The burden of proof, is on th e U.S. Food and Drug Administration to show a dietary supplement is unsafe, unlike for drugs, which cannot be approved until the manufacturer has demo nstrated safety and effectiveness.