An overview of herbal medicines and adverse events

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The use of herbal medicines has become a part of the US mainstream. Surveys suggest that about one-third of Americans use herbal products as medications. Some use herbal products with conventional medicine, others use them as a replacement. For western-trained health practitioners, their use poses a dilemma. Few practitioners have received herbal medicine education during their training. A great deal of herbal medicine information is written in foreign languages, but it is slowly becoming available in English. Some of the information is available as human clinical research reports, but most includes practitioner observations and historic use records.

Conventional drugs, regulated by the Food and Drug Administration (FDA), require quality assurance in manufacturing, labeling accuracy, demonstrated safety and efficacy before marketing, and post-marketing surveillance for adverse effects. They are available only by prescription from a trained, licensed prescriber. On the other hand, herbal medicines are regulated as food supplements under the Dietary Supplement Health and Education Act (DSHEA) of 1994. As such, there are no quality assurance requirements for manufacturing and labeling. Claims on the labels about efficacy or use are loosely regulated. Yet, DSHEA requires a disclaimer on package labeling: "This statement (about use of the product) has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease."

While efforts continue to establish and regulate good manufacturing practices for herbals, no standards or guidelines exist to assure quality. There are no provisions for pre-marketing approval to demonstrate safety and efficacy. Plant materials may be misrepresented or substituted to manufacturers, or may contain environmental or man-made contaminants. They may contain little or none of the plant material(s) stated on the label, or an entirely different plant material than is listed on the label. Some products may have been adulterated with conventional drugs. Since herbal medicines are freely available for sale, without limitation or medical consultation, a person with a significant health problem may, through self-guidance or untrained advice, postpone seeking adequate medical care. They may even abandon conventional drug therapy in favor of herbal therapy alone.

Herbal medicines appear relatively safe, but there is limited human research or prospective/retrospective data concerning adverse events and herbal-drug interactions. They are generally less potent than their pure drug relatives because they contain a mixture of many chemicals in small quantities. Thus, they often have a longer onset of action than conventional drugs. Although they appear to have a lower risk of adverse effects, herbal products are not free of risk.

Practitioners should learn about herbal medicines and other alternative therapies. Keep rational, reliable herbal medicine references on hand. Ask patients about their use of alternative therapies, including herbal medicines. Record all findings in the patient's medical record. Monitor patients carefully and report observations of adverse/unusual events. Ask patients to keep a daily diary of all therapies they use and bring it in for review at each visit to a healthcare professional.

ISMP will be working with herbal expert Dr. Forrest Batz, affiliated with the University of California San Francisco School of Pharmacy, to bring you regular information on herbal products. Our goal is to help practitioners identify and prevent herbal-related adverse events. Upcoming: reporting adverse events involving herbal products.