Twenty healthy people took warfarin for 3 days with and without pretreatment with American ginseng for 2 weeks. Ginseng was associated with a modest reduction in both the international normalized ratio (INR) and the warfarin area under the plasma concentration- time curve.1 - See more at: http://www.pharmacytimes.com/publications/issue/2004/2004-11/2004-11-4734#sthash.YCY2gf1X.dpuf