Oral Anticoagulant Therapy: Efficacy, Safety and the Low-Dose Controversy

The issue of optimal duration of oral anticoagulant therapy after a first episode of venous thromboembolism is still unresolved. However, recent data suggest that short (6 weeks to 3 months), intermediate (3- 6 months) or indefinite-term anticoagulant therapy should be adopted on the basis of the classification of patients into low-, intermediate- and high-recurrence-risk groups, respectively. Oral anticoagulants have been shown to effectively prevent cardioembolic stroke in nonvalvular atrial fibrillation. Recent data seem to suggest that their safety can be ameliorated with adequate risk stratification on the basis of clinical and echocardiographic features. After unstable angina and non-Q-wave myocardial infarction, oral anticoagulant therapy (INR range 2-3) combined with aspirin has been shown to be advantageous over aspirin alone, although at the cost of a slight increase in bleeding. Bleeding complications are major drawbacks of oral anticoagulant therapy thus limiting their generalized adoption in recognized indications. To sharply reduce the bleeding risk and need of laboratory control, the low- or fixed-dose oral anticoagulant approach has been evaluated. In primary prevention and in low or low-to-moderate thrombotic risk, minidose warfarin treatment has been shown to be advantageous. In secondary prevention, and in patients at high risk for recurrent venous or arterial thrombotic events, standard range (INR 2-3) or higher level of anticoagulation is needed.