Enoxaparin Dosing When Transitioning from Warfarin
When transitioning from warfarin to enoxaparin, the recommended therapeutic dosing is 1 mg/kg subcutaneously every 12 hours or 1.5 mg/kg once daily, with initiation once the INR falls below 2.0. 1, 2
Dosing Algorithm Based on Thromboembolism Risk
High-Risk Patients
- Dosing: Therapeutic enoxaparin at 1 mg/kg every 12 hours or 1.5 mg/kg once daily
- When to start: Begin when INR falls below 2.0
- Patient examples: Mechanical heart valves, recent VTE within 3 months, atrial fibrillation with prior stroke
- Duration: Continue until warfarin is restarted and INR reaches therapeutic range (typically 2.0-3.0)
Moderate-Risk Patients
- Dosing: Prophylactic to intermediate enoxaparin doses (40 mg twice daily or 0.5 mg/kg twice daily)
- When to start: Begin when INR falls below 2.0
- Patient examples: Atrial fibrillation without prior stroke, VTE >3 months ago
- Duration: Continue until warfarin is restarted and INR reaches therapeutic range
Low-Risk Patients
- Dosing: Prophylactic enoxaparin dose (40 mg once daily)
- When to start: Begin when INR falls below 1.5
- Patient examples: Atrial fibrillation with CHADS₂ score ≤1, remote history of VTE
- Duration: Continue until warfarin is restarted and INR reaches therapeutic range
Special Considerations
Renal Function Adjustments
- For CrCl <30 mL/min: Reduce dose to 1 mg/kg once daily 2
- For severe renal impairment: Consider unfractionated heparin as an alternative 2
Weight-Based Considerations
- For patients >100 kg: Maximum single dose generally should not exceed 150 mg
- For morbidly obese patients (BMI >40): Consider monitoring anti-Xa levels 2
Restarting Warfarin
- Resume previous stable warfarin dose when appropriate to restart anticoagulation 3
- Continue enoxaparin until INR reaches therapeutic range (≥2.0) for at least 24 hours 1
- For most patients, warfarin should be restarted at the previous stable dose rather than using a loading dose 4, 3
Monitoring Recommendations
- Check INR before starting enoxaparin to ensure it has fallen below 2.0
- Monitor platelet count during first 14 days of enoxaparin therapy
- For high-risk patients or those with renal impairment, consider monitoring anti-Xa levels (target 0.6-1.0 units/mL for twice-daily dosing or 1.0 units/mL for once-daily dosing) 2
Common Pitfalls and Caveats
- Avoid using enoxaparin in patients with history of heparin-induced thrombocytopenia 2
- Do not use fondaparinux for bridging therapy in patients undergoing PCI due to risk of catheter thrombosis 1
- Avoid simultaneous full-dose administration of both warfarin and enoxaparin; enoxaparin should be discontinued once INR reaches therapeutic range on warfarin 1
- Be aware that the FDA and manufacturer have strengthened warnings against using Lovenox for thromboprophylaxis in patients with prosthetic heart valves 1
This approach ensures appropriate anticoagulation coverage during the transition period while minimizing both thrombotic and bleeding risks based on patient-specific factors.