Ginseng Reduces Effects of Blood-Thinning Drug

Patients being treated with the blood-thinning drug Coumadin (warfarin) should probably avoid using ginseng, as the popular herb seems to reduce the drug’s effects, new research indicates.

Patients being treated with the blood-thinning drug Coumadin (warfarin) should probably avoid using ginseng, as the popular herb seems to reduce the drug’s effects, new research indicates. Among other indications, Coumadin is often given to patients with an irregular heartbeat called atrial fibrillation to reduce the risk of blood clots and stroke. A blood test called the INR is measured on a regular basis to ensure that the dose being given is not thinning the blood too much or too little. “The first evidence of a possible interaction between ginseng and (Coumadin) came from a widely cited case report published in 1997,” study author Dr. Chun-Su Yuan, from The University of Chicago, told Reuters Health. In that report, a patient on Coumadin “experienced a significant drop in the INR after using ginseng for 2 weeks. When the ginseng was stopped, the patient’s INR returned to the desired level.” Still, Yuan said that some subsequent studies in humans and animals have not supported an interaction between the two agents. To clarify the association, Yuan’s team conducted a study involving 20 healthy volunteers. In the 4-week study, the subjects took Coumadin during the first week, took American ginseng or placebo for the second and third weeks, and then took Coumadin during the fourth week. The researchers’ findings appear in the Annals of Internal Medicine. In agreement with the case report, ginseng use for two weeks was tied to a significant reduction in the INR, meaning that the blood was now less thin and more prone to clotting. Yuan said that past studies may have failed to show a drug interaction because ginseng was not used long enough. “One week of ginseng therapy is probably not enough to” turn on the liver enzymes that break down Coumadin — the apparent reason why the herb and the drug interact. Yuan favors not using ginseng at all for people on Coumadin treatment. When people take ginseng and the Coumadin dose is adjusted to compensate, “it’s possible that the INR could go dangerously high if the patient suddenly stops the ginseng.” (SOURCE: Annals of Internal Medicine: Reuters Health News: Anthony J. Brown, MD July 2004.)