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Warfarin is an oral anticoagulant used to prevent and treat thromboembolic disorders. It works by inhibiting vitamin K epoxide reductase, which reduces the synthesis of vitamin K–dependent clotting factors II, VII, IX, and X, as well as proteins C and S. Warfarin is a racemic mixture of R- and S-enantiomers, with S-warfarin being more potent and primarily metabolized by CYP2C9 in the liver. The anticoagulant effect develops gradually over several days.
Common indications include prevention of stroke in nonvalvular atrial fibrillation, treatment and prevention of deep vein
Dosing is individualized based on the target INR, typically 2.0–3.0 for many conditions; mechanical heart valves
Diet and drug interactions are important. Vitamin K intake should be kept consistent, as large fluctuations
Adverse effects include major bleeding and, less commonly, skin necrosis and purple toe syndrome. Warfarin is