The sodium salt form of warfarin, a coumarin and a vitamin K antagonist, with anticoagulant activity. Warfarin sodium inhibits both vitamin K and vitamin K epoxide reductases, thereby interfering with the cyclic interconversion of vitamin K epoxide to its reduced form, vitamin KH2. Vitamin KH2 is a cofactor for the carboxylation of glutamate residues on the N-terminal regions of vitamin K-dependent proteins. As a result, maturation of vitamin K-dependent coagulation factors II, VII, IX, and X and anticoagulant proteins C and S is inhibited. Without these coagulation factors, thrombogenesis and blood clot formation are prevented.