Therapeutic Range for the Control of Oral Anticoagulant Therapy

Oral anticogulants such as warfarin are effective for the prophylaxis of venous thromboembolism,1-3for the treatment of venous thromboembolism,4-6and for the prevention of systemic embolism from a cardiac source.7,8The role of anticoagulant therapy in acute myocardial infarction is controversial. Anticoagulants are effective in preventing venous thromboembolism and systemic embolism,7,9but their effect on recurrent infarction and death is inconclusive.10,11 Oral anticoagulant therapy is usually monitored by the one-stage prothrombin time (Quick time). The aim of anticoagulant therapy is to reduce the coagulability of blood into a therapeutic range within which the patient is protected against thrombosis while being exposed to a minimal risk of bleeding. The guidelines for the optimal therapeutic range for the control of anticoagulant therapy have been debated for 40 years and the recommendations have differed widely between experts. As a consequence, patients in North America are generally treated with