Warfarin is an anti-coagulant used to prevent heart attacks, strokes, and the formation of blood clots. It interferes with the use of vitamin K in the required carboxylation of several vitamin K-dependent proteins in the clotting cascade, preventing the initiation of clotting. (+)-Warfarin differs from (-)-warfarin by being five times less potent as a vitamin K antagonist. However the two isomers are metabolized in vivo by different pathways and (+)-warfarin has a longer terminal elimination half-life (35-58 hours) than (-)-warfarin (24-33 hours).