What is the recommended Lovenox (enoxaparin) dosing regimen for bridging therapy when interrupting Coumadin (warfarin)?

Recommended Lovenox Dosing for Bridging Warfarin Therapy

For patients requiring bridging therapy when interrupting Coumadin (warfarin), therapeutic-dose enoxaparin (Lovenox) should be administered at 1 mg/kg subcutaneously twice daily or 1.5 mg/kg once daily, with the last pre-procedure dose given 24 hours before surgery at half the total daily dose.

Patient Risk Stratification

First, determine if bridging is necessary based on thromboembolic risk:

High Thromboembolic Risk (Bridging Recommended)

• Mechanical heart valves (especially older-generation or mitral position)
• Recent venous thromboembolism (<3 months)
• Atrial fibrillation with CHADS₂ score ≥5
• Recent stroke or TIA (<3 months)
• Active cancer with thrombosis
• Severe thrombophilia syndromes

Low/Moderate Thromboembolic Risk (Bridging Generally Not Recommended)

• Atrial fibrillation with lower CHADS₂ scores
• VTE >3 months ago
• Bileaflet aortic valve without risk factors

Pre-Procedure Protocol

1. Stop warfarin 5 days before procedure 1

2. Start enoxaparin when INR falls below 2.0 (typically 3 days before procedure) 1, 2

3. Dosing options:

   • Therapeutic dose: 1 mg/kg twice daily or 1.5 mg/kg once daily 1
   • For renal impairment (CrCl <30 mL/min): Reduce to 1 mg/kg once daily 1

4. Last pre-procedure dose:

   • Administer the last dose 24 hours before surgery (not 12 hours) 1
   • Use half the total daily dose for this final pre-procedure dose 1

Post-Procedure Protocol

Timing of resumption depends on bleeding risk of the procedure:

Low-to-Moderate Bleeding Risk Procedures

• Resume warfarin evening of procedure or next day at maintenance dose 1
• Resume therapeutic-dose enoxaparin 24 hours after procedure 1, 2
• Continue enoxaparin until INR reaches therapeutic range (typically >2.0) 2

High Bleeding Risk Procedures

• Resume warfarin evening of procedure or next day at maintenance dose 1
• Delay therapeutic-dose enoxaparin for 48-72 hours post-procedure 1
• Consider prophylactic-dose enoxaparin (40 mg daily) for initial 48-72 hours for VTE prevention 1
• Resume therapeutic-dose enoxaparin when adequate surgical hemostasis is achieved 1
• Continue enoxaparin until INR reaches therapeutic range 2

Common Pitfalls to Avoid

1. Resuming therapeutic anticoagulation too early after high bleeding risk procedures can lead to major bleeding (rates as high as 20%) 1

2. Administering the last pre-procedure dose too close to surgery (less than 24 hours) can result in elevated anti-factor Xa levels during surgery, increasing bleeding risk 1

3. Failing to adjust dosing for renal impairment can lead to drug accumulation and increased bleeding risk 1

4. Not considering procedure-specific bleeding risk when determining resumption timing can lead to preventable bleeding complications 1

5. Continuing bridging therapy longer than necessary after warfarin has reached therapeutic levels increases bleeding risk without additional benefit 2

By following this structured approach to Lovenox bridging therapy when interrupting warfarin, you can minimize both thromboembolic and bleeding complications in the perioperative period.