Switching Study From Warfarin to Rivaroxaban

Days -6 and -5: 10 mg warfarin (Coumadin) once daily, dosage lower if the INR is already high on day -5; Days -4 to -1 (could be prolonged by two days): 2.5, 5, 10, 12.5 or 15 mg warfarin (Coumadin) once daily, dosage depending on INR

Days 0 to 3: 20 mg rivaroxaban once daily

Days 0 to 3: 1 tablet placebo, identical to active tablet

Day 5: 10 mg vitamin K (Konakion) once daily