Apixaban: A New Factor Xa Inhibitor for Stroke Prevention in Patients With Nonvalvular Atrial Fibrillation

Atrial fibrillation (AF) is an independent risk factor for ischemic stroke occurrence, severity, recurrence, and mortality. Anticoagulation therapy for the prevention of thromboembolism is critical in patients with AF who are at risk of stroke. Warfarin has been an efficacious anticoagulant for this purpose, but its use has been limited by frequent laboratory monitoring, drug interactions, unpredictable individual response, delayed onset of action, and bleeding. Apixaban is the second oral direct selective factor Xa inhibitor approved for the prevention of stroke/systemic embolism in patients with nonvalvular AF. It was significantly better than aspirin in reducing stroke (ischemic or hemorrhagic) or systemic embolism without increasing the risk of major bleeding in patients with AF who were at increased risk of stroke and for whom warfarin was unsuitable. In a randomized, double-blind trial that was originally designed to test for noninferiority, apixaban was superior to warfarin (target international normalized ratio 2-3) in preventing stroke or systemic embolism, caused less bleeding, and resulted in lower mortality in patients with AF. Apixaban has a half-life of about 12 hours, and the normal dosage is 5 mg orally twice daily. However, it may be reduced to 2.5 mg twice daily based on individual factors of the patient (age, renal function, and body weight) and the concomitant use of potent dual inhibitors of cytochrome P450 3A4 and P-glycoprotein. Similar to other novel oral anticoagulants (dabigatran and rivaroxaban), apixaban has no reversal agent for its anticoagulant effect. Overall, apixaban is a safe and efficacious alternative for stroke prophylaxis in high-risk patients who have AF and who are unable to achieve therapeutic goals with warfarin therapy.