Herbal therapies have become popular in the United States, with one in three Americans using some type of herbal remedy in the past year. A number of potential problems surround the use of these remedies. Patients are often unaware that about 25 percent of modern pharmaceuticals are derived from plants. Thus, the bioactivity of medicinal herbs is often underestimated. Patients who use herbal remedies often self-diagnose and may delay seeking medical attention. In addition, herbal remedies do not require evaluation and approval by the U.S. Food and Drug Administration, so information on side effects, drug interactions and product consistency is limited. Mar and Bent reviewed the literature on the 10 most commonly used herbs in the United States.

Their MEDLINE search was limited to English-language articles and human studies from 1966 to 1999. The most commonly used herbs are echinacea, St. John's wort, ginkgo biloba, garlic, saw palmetto, ginseng, goldenseal, aloe, Siberian ginseng and valerian. Evidence for the use of each herb was reviewed, and statements regarding efficacy were based on findings presented in systematic reviews and randomized controlled studies. For a detailed summary of the evidence on each herb, see the accompanying table on page 1840.

The authors conclude that the more reliable products will include labeling that lists the botanical name, the milligram dose, the batch or lot number, the expiration date and the name and address of the manufacturer. Patients should be advised to avoid using a wide variety of herbs concomitantly because herb-herb interactions are poorly understood. The starting dosage should be the lowest at which the desired effects occur. Long-term use of herbal products should be discouraged because long-term effects are unknown. For more resources and information about herbal therapies, see the accompanying table on page 1838.