Risk of Concurrent Use of Prescription Drugs with Herbal and Dietary Supplements in Ambulatory Care

Introduction: Little is known about the prevalence of herbal and dietary supplement (HDS) use among ambulatory patients who use prescription medications or about the risk of adverse drug events (ADEs) related to drug-HDS interactions. Methods: We conducted a secondary analysis of a study of patients who received prescription medications at four primary care practices. We used chart reviews and patient interviews to identify potential drug-HDS interactions, and we used MICROMEDEX to classify interactions. Results: A total of 101 of 657 patients (15.4 percent) reported using HDS, including echinacea (21.8 percent), ginkgo biloba (13.9 percent), glucosamine (13.9 percent), omega-3 fatty acids (12.9 percent), garlic (7.9 percent), St. John’s wort (6.9 percent), and ginseng (6.9 percent). Although we found no increased rate of ADEs among HDS users compared to nonusers, 14 percent of users had potentially dangerous interactions with their prescription drugs. Conclusion: HDS use is common in adult ambulatory care. The risk of interactions between these agents and prescription medications is worrisome. Introduction In 1994, Congress defined a dietary supplement as a product taken by mouth that contains a “dietary ingredient” intended to supplement the diet. The “dietary ingredients” in these products may include vitamins, minerals, herbs or other botanicals, amino acids, and substances, such as enzymes, organ tissues, glandulars, and metabolites. Dietary supplements can also be extracts or concentrates, and they may be found in forms such as tablets, capsules, softgels, gelcaps, liquids, and powders. The use of herbal and dietary supplements (HDS) has grown rapidly in the United States. In 2001, consumers spent $17.8 billion on dietary supplements, including $4.2 billion of this amount for herbs. A comparison of the results of the National Health Interview Survey in 2002 with a 1997 survey of complementary and alternative medicine use 4 found a 50 percent increase in Americans’ use of herbal supplements, from 12.1 percent of adults in 1997 to 18.6 percent—or 38 million individuals—in 2002. Most dietary supplements are unlicensed, and manufacturers are not required to demonstrate efficacy, safety, or quality. Although herbs are often promoted as natural and therefore