American Ginseng Can Reduce the Effects of Warfarin

Coumadin® (warfarin) is a prescription medication that is widely used to prevent blood from forming clots. It works by blocking the action of Vitamin K, which helps create the enzymes that coagulate blood. The anticoagulant effect of warfarin can be affected by many factors, including changes in the intake of Vitamin K or using substances that might affect the clotting enzymes.

Ginseng is felt by some to help with energy and vitality, especially during stress. Some feel it can improve memory and "brain power." There has been little solid evidence to support this, however. In a paper published in The Annals of Internal Medicine (2004; 141:23-27) Dr. Yuan and his study team had twenty patients take warfarin. In the first week the medication was given and the INR checked. In the second week, 12 of the participants began also taking American ginseng, while 8 began taking a placebo. Neither the participants or the researchers knew which patient was in which group during the study.

When the scientists looked at the data, they found that the group taking the ginseng had a lowered effectiveness of the warfarin. It doesn't appear that the ginseng has an effect on Vitamin K, however, and the researchers speculated that ginseng may affect enzymes in the liver directly. They do note that their study participants were younger than most people who are on anticoagulant medication. There is also a question of whether ginseng products other than the American variety act the same way.

What this means for you

This is another study that shows how important it is for patients using any prescription medication to consult their physician about all of the supplements that they are taking. This is especially true with medications that have high risk of side effects, like warfarin.

First posted: May 9, 2006