An 86-year-old woman (weighing 55 kg) presented to the emergency department with persistent epistaxis. She had a history of atrial fibrillation and had been taking rivaroxaban, 20 mg, once daily, for stroke prevention for 1 year. She also had a history of peripheral arterial disease and had been taking aspirin, 80 mg, once daily for primary prevention for 9 months. Her medical history also included a bioprosthetic heart valve replacement 4 years before presentation. On admission, her creatinine clearance was 21 mL/min according to the Cockroft-Gault equation; hemoglobin, 9.4 g/dL; and prothrombin time Quick value, 30% (normal range, 75%-100%).