Apixaban Compared With Warfarin for Stroke Prevention in Atrial Fibrillation

D ow nloaded from DOI: 10.1161/CIRCULATIONAHA.113.003132 2 Clinical guidelines1,2 advocate the use of oral anticoagulation, whether a vitamin K antagonist (VKA) or one of the novel agents, for stroke prevention in patients with atrial fibrillation (AF) who have one or more risk factor for stroke. The benefits of traditional oral anticoagulants (VKAs), in terms of a reduction in stroke and major bleeding events, are only experienced over a narrow therapeutic window (International Normalised Ratio (INR) of 2.0 to 3.0). Their intricate pharmacokinetic profile with a slow onset and offset of action and numerous drug-, food- and alcohol-interactions, as well as genetic, ethnicity, and age-related differences in dose response, necessitates regular INR monitoring3. The efficacy and safety of VKAs strongly depends upon the percentage of time in the therapeutic range (TTR) (INR 2.0 to 3.0), with maximum benefits evident when the TTR is 70