Commonly Used Dietary Supplements Affect Warfarin Safety and Efficacy
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According to study results presented at Heart Rhythm 2010—the Heart Rhythm Society’s 31st Annual Scientific Sessions—8 of the 10 dietary supplements used most commonly by American consumers have been reported to interact with warfarin.
The study focused on the top 20 herbal and 20 nonherbal supplements in the United States, based on 2008 sales data. Researchers from Intermountain Health Center in Salt Lake City, Utah, searched the Natural Medicines Comprehensive Database, AltMedDex (Micromedex), and various Natural Standard databases for relevant clinical trials and case reports that documented a supplement–drug interaction with reported changes in International Normalized Ratio (INR), bleeding risks, or thromboembolic events.
Of the 40 top-selling supplements, 35% were associated with a clinically important change in INR, 64% were found to potentiate a bleeding risk, and 36% were reported to decrease the effectiveness of warfarin. Specifically, cranberry, garlic,
ginkgo, and saw palmetto all have been linked to bleeding events. Glucosamine/chondroitin, essential fatty acids, multiherb products, and evening primrose oil all may increase prothrombin times; coenzyme Q10, ginseng, melatonin, soy, and St. Johns’s wort all may decrease prothrombin times.
Heart Rhythm. 2010;7(5 suppl 1):S4.