Warfarin Dosing After Rivaroxaban Discontinuation
When transitioning from rivaroxaban to warfarin in patients with atrial fibrillation or venous thromboembolism, start warfarin at 5 mg daily (or 2.5-7.5 mg daily based on age, body weight, and bleeding risk) and continue rivaroxaban for at least 2 days after initiating warfarin until the INR reaches the therapeutic range of 2.0-3.0. 1
Transition Protocol
The key principle is avoiding gaps in anticoagulation while preventing excessive overlap bleeding risk. 1
Step-by-Step Approach:
- Start warfarin at a typical initial dose of 5 mg daily while the patient is still taking rivaroxaban 1
- Continue both medications concurrently until the INR is therapeutic (2.0-3.0, ideally targeting 2.0-2.5 when combined with antiplatelet therapy) 1
- Discontinue rivaroxaban only after the INR reaches ≥2.0 on at least two consecutive measurements 1
- Monitor INR more frequently during the transition period (every 2-3 days initially) to ensure therapeutic anticoagulation is maintained 1
Initial Warfarin Dosing Considerations
Standard Starting Dose:
- Most patients: 5 mg daily is the conventional starting dose 1
- Elderly patients (≥75 years): Consider 2.5-5 mg daily to reduce bleeding risk 1
- Patients with low body weight (≤60 kg): Consider 2.5-5 mg daily 1
Target INR Range:
- Standard target: INR 2.0-3.0 for atrial fibrillation and venous thromboembolism 1
- Lower end of range (2.0-2.5) is reasonable when combined with antiplatelet therapy or in patients at higher bleeding risk 1
Critical Pitfalls to Avoid
The most dangerous error is stopping rivaroxaban before warfarin reaches therapeutic levels, which creates a gap in anticoagulation and increases stroke/thrombosis risk. 1 This is particularly concerning because rivaroxaban has a short half-life (5-9 hours in young patients, 11-13 hours in elderly), and inadequate anticoagulation can occur within 24 hours of the last dose. 1
Another common mistake is excessive overlap causing major bleeding. While overlap is necessary, the duration should be minimized by checking INR frequently (every 2-3 days) during the transition. 1
Special Populations
Renal Impairment:
- CrCl 30-50 mL/min: Standard warfarin dosing with more frequent INR monitoring 1
- CrCl 15-30 mL/min: Consider lower initial warfarin doses (2.5-5 mg) and monitor INR every 2-3 days 1
- CrCl <15 mL/min or dialysis: Warfarin is preferred over rivaroxaban in this population 1
Patients on Antiplatelet Therapy:
- Target the lower end of the INR range (2.0-2.5) to reduce bleeding risk when warfarin is combined with aspirin or clopidogrel 1
- Consider discontinuing aspirin if the patient is on dual therapy with warfarin and a P2Y12 inhibitor after PCI, depending on the time elapsed since the procedure 1
Why This Transition is Necessary
Warfarin remains the standard anticoagulant when rivaroxaban is contraindicated or fails, particularly in patients with severe renal impairment (CrCl <30 mL/min), mechanical heart valves, or when cost is prohibitive. 1 Warfarin demonstrated consistent efficacy in preventing stroke in atrial fibrillation with proper INR management (time in therapeutic range >65-70%). 1
However, warfarin requires careful dose adjustment because it has a narrow therapeutic window, significant food and drug interactions, and genetic variability in metabolism. 1 The quality of anticoagulation management directly impacts outcomes—poor INR control (time in therapeutic range <58%) significantly reduces warfarin's effectiveness compared to DOACs like rivaroxaban. 1