A 66-year-old woman with atrial fibrillation is not currently on anticoagulation. Which medication would be most appropriate for stroke prevention in this patient?

• A. Apixaban 5 mg twice daily
• B. Warfarin
• C. Rivaroxaban 20 mg once daily
• D. Clopidogrel

Answer: (A)

In nonvalvular atrial fibrillation, the goal is to prevent cardioembolic stroke with an oral anticoagulant. Direct oral anticoagulants (DOACs) are preferred over warfarin because they offer similar protection with easier use and a lower risk of intracranial bleeding. Among the DOACs, apixaban has the best balance of efficacy and safety, showing in large trials that it reduces stroke and systemic embolism while causing less major bleeding, particularly intracranial bleeding, compared with warfarin. The standard dose is 5 mg twice daily unless dose reduction criteria apply; this patient is 66 years old, so she does not meet those criteria. Clopidogrel alone does not provide adequate stroke prevention in AF. Rivaroxaban is an alternative DOAC but can carry a higher risk of major GI bleeding in some patients. Therefore, starting apixaban at 5 mg twice daily is the most appropriate option for stroke prevention in this patient.