Researchers from the University of Chicago report in the Annals of Internal Medicine that ginseng, one of the best selling herbal supplements in the United States, interferes with warfarin, a drug commonly used to prevent blood clots.
The researchers encourage anyone who takes both ginseng and warfarin, also known as Coumadin©, to notify his or her doctor and urge doctors to ask patients on warfarin if they are taking ginseng.
"Warfarin has a narrow therapeutic index," said study author Chun-Su Yuan, M.D., Ph.D., "which means precise dosing is crucial."
The blood-thinner warfarin, taken once a day by about 3 million people in the United States, is used to prevent blood clots from forming or growing larger. It is often prescribed for patients with certain types of irregular heartbeat, those who have had a heart attack or undergone heart valve replacement surgery. It prevents the formation of substances that cause clots.