Herbal medicine in the United States: review of efficacy, safety, and regulation: grand rounds at University of California, San Francisco Medical Center

Abstract

Introduction: Herbal products have gained increasing popularity in the last decade, and are now used by approximately 20% of the population. Herbal products are complex mixtures of organic chemicals that may come from any raw or processed part of a plant, including leaves, stems, flowers, roots, and seeds. Under the current law, herbs are defined as dietary supplements, and manufacturers can therefore produce, sell, and market herbs without first demonstrating safety and efficacy, as is required for pharmaceutical drugs. Although herbs are often perceived as "natural" and therefore safe, many different side effects have been reported owing to active ingredients, contaminants, or interactions with drugs.

Results: Unfortunately, there is limited scientific evidence to establish the safety and efficacy of most herbal products. Of the top 10 herbs, 5 (ginkgo, garlic, St. John's wort, soy, and kava) have scientific evidence suggesting efficacy, but concerns over safety and a consideration of other medical therapies may temper the decision to use these products.

Conclusions: Herbal products are not likely to become an important alternative to standard medical therapies unless there are changes to the regulation, standardization, and funding for research of these products.

Figure 1

The bottom line (at AU 0.00) shows the reference standard with the labeled flavonol gylcosides: rutin, quercitrin, quercetin, kaempferol, and isorhamnetin. Note that the 5 different ginkgo products (A, B, C, D, E) have substantial variation in the amount of the various glycosides, as reflected by the height of the chromatogram peak. There was more than a 25-fold variation in some constituents between products. (Reproduced with permission from Dubber MJ, Kanfer I. High-performance liquid chromatographic determination of selected flavonols in Ginkgo biloba solid oral dosage forms. J Pharm Pharm Sci. Sep 24 2004;7(3):303–309)