Ginseng and other herbal medicines that interact with warfarin.

The consumption of herbal medicines is increasing rapidly worldwide. Ginseng is one of the most widely used herbal medicines in the world, for its physical, mental and sexual effects. It is one of the best-selling herbs in the United States [1]. The recent report that ginseng may paradoxically decrease the anticoagulant effect of warfarin [1] was the third such report, the first two being published in 1997 [2] and 2003 [3]. There are several species of ginseng, the four major ones being Chinese or Korean ginseng (Panax ginseng), Siberian ginseng (Eleutherococcus senticosus), American ginseng (Panax quinquefolium) and Brazilian ginseng (Pfaffia paniculata) [2,4,5], containing various amounts of ginsenosides [6]. Ginseng usually tends to cause bleeding and thus may potentiate the anticoagulant effect of warfarin [7–9]. Besides ginseng, there are other herbal medicines that may potentiate the action of warfarin, such as danshen [10–14] and dong quai [15]. Because herbal prescriptions are often combined preparations, causal attribution is often difficult [16]. Because 33% of Chinese patients take herbal medicines [17], it is very important for every physician to be aware of the possibility of such drug interactions when excessive bleeding, unsuspected increase or decrease of the prothrombin time or international normalized ratio, or difficulty in regulating the warfarin dosage that is encountered in any patients on warfarin therapy who have otherwise been under good anticoagulant control [10].