About Warfarin Synthetic coumarin derivative , Vitamin K Antagonist, Anticoagulant. Mechanism of Action of Warfarin It exerts it`s pharmacological action by inhibiting regeneration of active hydroquinone from vitamin K and also behaves as a competitive antagonist of vitamin K. Thus the drug interacts with synthesis of vitamin K derived clotting factors (factors- II, VII, IX, and X.) in a dose dependent manner and reduce their plasma levels. Vitamin K-hydroquinone is required for final step of gama-carboxylation of descarboxy forms of these factors. This carboxylation is essential for the ability of the clotting factors to bind Ca2+ and to get bound to phospholipid surfaces and ultimately involve in coagulation cascade. Indications for Warfarin 1. Thromboembolism, 2. Pulmonary embolism 3. Transient ischemic attack 4. Atrial fibrillation 5. Rheumatic heart disease 6. Deep vein thrombosis