A 67-year-old man with hypertension and type 2 diabetes presents for follow-up after new paroxysmal atrial fibrillation was documented on ambulatory ECG. He has no valvular disease, no stroke history, creatinine clearance 58 mL/min, and no active bleeding. CHA₂DS₂-VASc score is 3. What is the most appropriate next step to reduce his stroke risk?