Apixaban in the prevention of stroke and systemic embolism in nonvalvular atrial fibrillation.

Conventional anticoagulant therapies can significantly reduce the risk of stroke and related complications in patients with atrial fibrillation (AF). Classic oral anticoagulants based on vitamin K antagonism have shown effectiveness in the prevention of thromboembolic complications in this clinical setting. Unfortunately, vitamin K antagonists that have shown effectiveness in the prevention of thromboembolic complications in patients with nonvalvular AF hold inherent limitations including delayed onset of action, narrow therapeutic index, variability of their response, need for repeated control and numerous interactions with food and other drugs. Since the frequency of stroke related to AF increases with age, guidelines from different scientific societies advise that the risk of bleeding for a patient should be quantified before exposure to anticoagulation and balanced against the risk of stroke with and without anticoagulation. A consequence of assessing this risk/benefit balance is that not all patients with AF at thromboembolic risk receive adequate anticoagulant treatment. Apixaban is a new oral anticoagulant with a direct, specific and reversible inhibitory action on coagulation factor Xa and with demonstrated safety and efficacy in the prophylaxis and treatment of venous thromboembolism in several clinical studies involving thousands of patients subjected to major orthopedic surgery. Results of two large phase III trials have demonstrated the efficacy and safety of apixaban compared with aspirin or warfarin, in the prevention of stroke in patients with AF. Apixaban demonstrated superiority over classic vitamin K antagonists on the previously specified outcomes of stroke, systemic embolism, major bleeding and death. For those patients unsuitable for treatment with vitamin K antagonists because of an excessive bleeding risk, apixaban showed more efficacy than aspirin in stroke prevention with a not statistically significant modest increase of major bleeding.