• Antagonist to vitamin K; Blocks the biosynthesis of factors VII, IX, X, and prothrombin It takes days to be effective Therapeutic uses - Long-term prophylaxis of thrombosis • Prevention of venous thrombosis and associated pulmonary embolism • Prevention of thromboembolism (in patients with prosthetic heart valves) • Prevention of thrombosis during atrial fibrillation Adverse effects • Hemorrhage (Fetal hemorrhage in pregnant) • Not to be Used during lactation Drug interactions • Drugs that increase anticoagulant effects • Drugs that promote bleeding