Systematic Overview of Warfarin and Its Drug and Food Interactions

Abstract

Warfarin is the most commonly used oral anticoagulant in North America and has established efficacy for the prevention of thromboembolic events in patients with chronic atrial fibrillation, prosthetic heart valves, venous thromboembolism, and coronary artery disease.^1-4 The drug is a racemic mixture of 2 optically active isomers, though the S-enantiomer is approximately 5 times more potent than the R-enantiomer. Warfarin exerts its effect by lowering the amount of active vitamin K available for the activation of clotting factors II, VII, IX, and X.⁵ Both effectiveness and safety (primarily risk of bleeding) are related to blood international normalized ratio (INR) values. Monitoring of INR and dose adjustments of warfarin are frequently required, influenced by changes in concomitant medications, diet, alcohol consumption, acute illness, liver disease, and unknown factors.⁵