Bridging Enoxaparin Dose Before Acenocoumarol
For patients requiring bridging anticoagulation with enoxaparin before starting acenocoumarol, use therapeutic-dose enoxaparin at 1 mg/kg subcutaneously every 12 hours (or 1.5 mg/kg once daily) in high thromboembolic risk patients, starting 1 day after acenocoumarol interruption, and continue both agents overlapping for at least 5 days until INR reaches 2.0-3.0. 1
Risk-Stratified Dosing Protocol
High Thromboembolic Risk Patients
Therapeutic-dose enoxaparin is mandatory for patients with:
- Mechanical prosthetic heart valves 1
- Atrial fibrillation with additional risk factors 1
- Recent venous thromboembolism (<3 months) plus thrombophilia 1
- Biological prosthetic valves or mitral valve repair within 3 months 1
Dosing regimen: 1 mg/kg subcutaneously every 12 hours, starting 1 day after acenocoumarol discontinuation 1. The European Heart Journal guidelines specifically note this timing differs from warfarin (which requires 2 days) due to acenocoumarol's shorter half-life 1.
Moderate/Low Thromboembolic Risk Patients
Prophylactic-dose enoxaparin: 40 mg subcutaneously once daily for patients at lower risk 1. However, the distinction between prophylactic dosing (40 mg daily) and therapeutic dosing (1 mg/kg every 12 hours) is critical—confusing these represents a common and dangerous error 2.
Timing and Transition Protocol
Pre-Procedure Management
- Stop acenocoumarol 5 days (five doses) before surgery 1
- Start enoxaparin 1 day after acenocoumarol interruption when INR falls below therapeutic range 1
- Administer last enoxaparin dose at least 12 hours before the procedure 1
- **Verify INR <1.5 on day of procedure**; postpone if INR >1.5 1
Post-Procedure Management
- Resume enoxaparin 1-2 days after surgery at the pre-procedural dose, depending on hemostatic status, but at least 12 hours post-procedure 1
- Restart acenocoumarol on day 1 or 2 post-surgery if patient can take oral therapy 1
- Use a boost dose strategy: Give maintenance dose plus 50% extra for two consecutive days, then return to maintenance dose 1
- Continue enoxaparin until INR returns to therapeutic range (2.0-3.0) for at least 24 hours, typically requiring 5-10 days of overlap 1
Weight-Based Dosing Table
The European Heart Journal provides specific enoxaparin dosing by weight for high-risk patients 1:
Twice-daily therapeutic dosing:
- <50 kg: 2000 IU (approximately 20 mg) every 12 hours 1
- 50-69 kg: Standard 1 mg/kg every 12 hours 1
- 70-89 kg: Standard 1 mg/kg every 12 hours 1
- 90-100 kg: Standard 1 mg/kg every 12 hours 1
Once-daily prophylactic dosing (low-risk patients):
- All weight ranges: 40 mg (4000 IU) once daily 1
Special Populations and Dose Adjustments
Renal Insufficiency
Reduce enoxaparin dose to 1 mg/kg once daily (instead of every 12 hours) if creatinine clearance <30 mL/min 1. Consider unfractionated heparin instead of enoxaparin in severe renal impairment due to accumulation risk 2.
Cancer Patients
Enoxaparin is preferred over acenocoumarol for long-term treatment in oncology patients with venous thromboembolism due to lower recurrence rates 2. Continue enoxaparin for at least 6 months rather than transitioning to acenocoumarol 1, 2.
Mechanical Heart Valve Patients
Research specifically in acenocoumarol-treated patients with mechanical heart valves demonstrates that standard enoxaparin dosing (1 mg/kg every 12 hours) is effective and safe, with no thromboembolic events reported in a prospective cohort 3. Mean anti-Xa activity achieved was 0.58 IU/mL (median 0.51), which is within therapeutic range 3.
Monitoring Considerations
Anti-Xa Monitoring
Routine anti-Xa monitoring is generally not necessary for standard-dose enoxaparin 2.
Consider anti-Xa monitoring in:
Therapeutic anti-Xa range: 0.3-0.7 IU/mL for enoxaparin (measured 4 hours post-dose for twice-daily dosing) 2.
INR Monitoring
Check INR daily once acenocoumarol is restarted until stable in therapeutic range (2.0-3.0) for two consecutive measurements 2.
Evidence Quality and Clinical Outcomes
Multiple prospective studies support this approach with excellent safety profiles:
- No thromboembolic events in 82 patients with mechanical valves bridged with enoxaparin during acenocoumarol interruption 3
- 0.5% thrombosis rate in 49 patients receiving therapeutic-dose enoxaparin bridging, with 0% mortality 4
- 0% thromboembolic events in 779 patients using risk-adapted enoxaparin dosing 5
- 2.9% plausibly-related thromboembolic events in 140 cardiac surgery patients, with 2.1% major bleeding 6
Critical Pitfalls to Avoid
Do not abruptly stop acenocoumarol without bridging therapy in high-risk patients—this creates a prothrombotic window 2.
Do not confuse prophylactic enoxaparin doses (40 mg daily) with therapeutic doses (1 mg/kg every 12 hours)—this is a common and potentially catastrophic error 2.
Do not reduce enoxaparin dose for minor bleeding without specialist consultation—premature dose reduction increases thrombotic risk 2.
Do not stop enoxaparin before INR is therapeutic—maintain overlap until INR ≥2.0 for at least 24 hours 1.
Do not use the same timing for acenocoumarol and warfarin—acenocoumarol requires starting enoxaparin 1 day after interruption, while warfarin requires 2 days 1.