... against rats and mice and is popular for this purpose. Warfarin is a synthetic derivative of , a 4-hydroxycoumarin-derived anticoagulant ... (not to be confused with Coumadin, a brand name for warfarin). Coumarin itself has no effect on clotting, or upon the ... action of warfarin. Warfarin and related 4-hydroxycoumarin-containing molecules decrease blood by inhibiti ...