Coumarins have been the mainstay of oral anticoagulant therapy for more than 50 years.1 Their effectiveness has been established by well-designed clinical trials for primary and secondary prevention of venous thromboembolism, for prevention of systemic embolism in patients with prosthetic heart valves or atrial fibrillation, for primary prevention of acute myocardial infarction in high-risk men, and for prevention of stroke, recurrent infarction, or death in patients with acute myocardial infarction.1 The effectiveness and safety of oral anticoagulants are less clear in patients with cerebrovascular disease. In these patients, high-intensity oral anticoagulation (international normalized ratio [INR], 3.0-4.5) is associated with an unacceptable risk of intracranial bleeding,2 and low-intensity oral anticoagulation (INR, 1.4-2.8) is not more effective and is less convenient than aspirin therapy (325 mg/d).3
O'Donnell M, Hirsh J. Establishing an Optimal Therapeutic Range for Coumarins: Filling in the Gaps. Arch Intern Med. 2004;164(6):588–590. doi:10.1001/archinte.164.6.588
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