Drug concentration

Drug concentration or activity in the blood may be increased if a dietary supplement aids the absorption of the drug or if it inhibits enzyme destruction or elimination of the drug. Conversely, drug concentration and activity in the blood may be decreased if the dietary supplement binds components of the drug, thus preventing its absorption, or if the dietary supplement stimulates production and/or activity of enzymes that destroy the drug. Some of the most popular dietary supplements may interact with drugs. A 2004 study at the University of Chicago Medical Center, which was funded by the National Institutes of Health and the Tang Center for Herbal Medicine Research, found that ginseng, which is commonly taken to enhance well-being, reduce fatigue, and improve immune response, decreased the effect of the anticoagulant warfarin. People who consumed warfarin and ginseng had an increased incidence of blood clots and therefore an increased risk of deep vein thrombosis. Because of ethical reasons, this study was done in healthy individuals, but the researchers believed that the results could be applied to those taking warfarin for prevention of deep vein thrombosis.