How does ginseng interact with warfarin?
Warfarin is a commonly used drug that decreases the clotting activity of the blood by thinning it in order to prevent the development of clots or to prevent existing clots from getting bigger. Warfarin has a very narrow therapeutic index. In other words, the effective dose that is safe and the dose that may cause adverse events are very close. So if you are above the effective dose or below the effective dose, it may cause different pharmacologic activities. Tests for blood coagulation, or clotting, levels are done frequently in patients on wafarin to ensure the dose is appropriate. Other drugs and supplements may change the concentration of the warfarin in the blood, leading to clinical consequences. For example, the blood thinning effect may not be achieved, or someone may have bleeding because the blood won't clot.
After people in our study took ginseng for two weeks, we found that they had a lower blood level of warfarin, and that warfarin had less of an effect on blood clotting than it did it people who took the placebo.
Who might be at higher risk for adverse effects or interactions?
Studies show, in general, that the incidence of adverse effects of herbs is much lower than that in prescription medications. So dietary supplements are fairly safe. But people who have medical conditions, as well as elderly people, pregnant women, and children, should be careful with dietary supplements.
