Warfarin Versus New Agents: Interpreting the Data

Stroke prevention in atrial fibrillation (AF) is a rapidly expanding indication for lifelong oral anticoagulation. The vitamin K antagonists (VKAs) effectively prevent stroke, but are notoriously difficult to manage and are associated with frequent adverse events. These factors account for the widespread underuse of warfarin for patients with AF who are qualified candidates for therapy. New oral anticoagulants with different mechanisms of action are beginning to exit phase III trials and may replace the VKAs for a number of indications, especially AF. The oral direct thrombin and Xa inhibitors are furthest along in development. Dabigatran etexilate, a thrombin inhibitor, has recently shown excellent outcomes in the prevention of stroke in patients with AF. The oral Xa inhibitors are still in phase III trials for stroke prevention in AF, but results from trials for other indications look promising. These short-acting, short-duration, unmonitored drugs are not without limitations and potential adverse effects. The perceived drawbacks of the VKAs may actually be assets in the management of patients with AF, and the pros and cons of each class of drug must be taken into account as physicians consider or patients request transition to a new class of oral anticoagulants.