How to Transition from Warfarin to Apixaban
Discontinue Warfarin and Start Apixaban When INR Falls Below 2.0
Discontinue warfarin and initiate apixaban when the INR drops below 2.0 1, 2. This threshold balances the waning anticoagulant effect of warfarin against apixaban's rapid onset of action (peak levels at 3 hours), avoiding dangerous overlap that increases bleeding risk 1.
Step-by-Step Transition Protocol
1. Stop Warfarin
- Discontinue warfarin and monitor INR 2
- The INR typically falls below 2.0 within 3-5 days after stopping warfarin, depending on the patient's dose and individual metabolism 3
2. Monitor INR Until Below 2.0
- Check INR every 1-2 days after stopping warfarin 1
- Do not start apixaban while INR remains ≥2.0, as this creates excessive anticoagulation from both drugs simultaneously 1
- Do not wait for INR <1.5—the guideline-recommended threshold is INR <2.0 1
3. Initiate Apixaban
- Start apixaban when INR <2.0 1, 2
- Do not overlap both medications—begin apixaban only after warfarin is discontinued and INR has fallen appropriately 1
4. Dosing
For atrial fibrillation:
- Standard dose: 5 mg twice daily 2
- Reduced dose: 2.5 mg twice daily if patient has at least 2 of the following: age ≥80 years, body weight ≤60 kg, or serum creatinine ≥1.5 mg/dL 2
For VTE treatment:
- 10 mg twice daily for 7 days, then 5 mg twice daily 2
Critical Contraindications—Do Not Switch
Absolute Contraindications
- Mechanical heart valves: These patients must remain on warfarin 4, 3
- Moderate-to-severe mitral stenosis: Warfarin is required 4, 3
Relative Contraindications (Exercise Caution)
- End-stage renal disease or hemodialysis: Warfarin is preferred over apixaban in this population 3
- Thrombotic antiphospholipid syndrome: Apixaban may not prevent recurrent thrombosis (especially strokes) as effectively as warfarin 5
Post-Transition Management
Monitoring Requirements
- No routine INR monitoring is needed after switching to apixaban 3
- Assess renal function before initiating apixaban and periodically during treatment, especially in elderly patients 3
- Evaluate bleeding risk factors at regular intervals 3
Patient Education
- Emphasize strict adherence: Apixaban has a 9-14 hour half-life, meaning missed doses leave patients without anticoagulation protection 1
- If a dose is missed, take it as soon as possible on the same day; do not double the dose 2
Common Pitfalls to Avoid
- Starting apixaban too early (INR ≥2.0): This creates dangerous overlap with excessive anticoagulation 1
- Waiting for INR <1.5: This unnecessarily delays apixaban initiation and leaves patients underanticoagulated 1
- Simultaneous administration: Never start both medications at the same time given apixaban's rapid onset 1
- Failing to verify indication: Always confirm the patient does not have mechanical valves or moderate-to-severe mitral stenosis before switching 3
- Inadequate patient counseling: Patients must understand the importance of twice-daily dosing without interruption 1
Special Considerations
Renal Impairment
- Apixaban can be used in patients with creatinine clearance 25-30 mL/min with standard dosing (5 mg twice daily or 2.5 mg twice daily based on dose-reduction criteria) 6
- Apixaban demonstrated less bleeding than warfarin in patients with advanced chronic kidney disease (CrCl 25-30 mL/min) 6