The Scylla and Charybdis of Oral Anticoagulant Treatment

Treatment with oral anticoagulant drugs (i.e., coumarin derivatives such as warfarin) is effective in the prevention of venous and arterial thromboembolism. In patients with atrial fibrillation, anticoagulation reduces the risk of stroke by 70 percent.1 The principal problem with anticoagulation is the variability of the effect of coumarin derivatives on the hemostatic system; patients may require very different doses (up to 10-fold differences) to reach the same level of anticoagulation, and the required dose may also vary over time in an individual patient. Since underanticoagulation is ineffective and overanticoagulation may lead to hemorrhage, anticoagulant treatment needs to be monitored and . . .