New developments in anticoagulation for atrial fibrillation.

The incidence of stroke in patients with atrial fibrillation (AF) is five times greater than that in age-matched controls. Warfarin reduces this incidence by two thirds and is the most effective agent for this indication. However, despite its efficacy, warfarin management is tedious and is useful only in a subsegment of the population who needs anticoagulation and has no contraindications. Many agents are poised to replace warfarin as an effective anticoagulant for stroke prevention in AF. The direct thrombin inhibitor dabigatran is furthest along in clinical development, followed by the factor Xa inhibitors rivaroxaban and apixaban. All these agents seem effective, and none appears mechanistically superior over another. Dabigatran's advantage is that it was tested in two dosages in a phase 3 evaluation based on earlier phase 2 studies in patients with AF, whereas dosage data for the other agents were extrapolated from phase 2 programs for venous thromboembolism prevention. The vitamin K antagonist ATI-5923 offers clinical benefits similar to warfarin's, but with no or fewer drug-drug interactions, potentially greater time in therapeutic range, and probably less need for dose adjustment and laboratory monitoring. It challenges the newer mechanistic agents in efficacy and raises the bar for comparison in future head-to-head trials. Further analysis and clinical trial testing are still needed to determine whether one or all of these agents are effective anticoagulants for stroke prevention in patients with AF.