Which of the following is the mechanism of action of warfarin?

Warfarin inhibits vitamin K-dependent coagulation factor synthesis. These include factors II, VII, IX, and X, as well as protein C and S. Warfarin acts to increase the prothrombin time. Factors XI and XII are not vitamin K-dependent factors. Therefore, warfarin does not inhibit their synthesis. Activation of antithrombin III is a mechanism of action used by heparin. It acts to prolong the paial thromboplastin time. Fibrinolysis is a mechanism of action used by thrombolytic agents such as streptokinase and urokinase. These agents conve plasminogen to plasmin, promoting fibrinolysis. Inhibition of antithrombin III would promote clot formation. The goal of anticoagulation is to prevent clot formation. Ref: Weitz J.I. (2011). Chapter 30. Blood Coagulation and Anticoagulant, Fibrinolytic, and Antiplatelet Drugs. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds), Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e.