Restarting Acenocoumarol After INR Normalization to Achieve Target INR 3.0
Restart acenocoumarol immediately at 50-75% of your previous maintenance dose without a loading dose, and initiate bridging anticoagulation with therapeutic-dose low molecular weight heparin (LMWH) or unfractionated heparin until INR reaches 2.0 or above for two consecutive days. 1, 2
Immediate Anticoagulation Strategy
Bridging Anticoagulation is Required
Bridging is mandatory for patients requiring a target INR of 3.0, as this indicates high thromboembolic risk (mechanical heart valves, recurrent thromboembolism, or antiphospholipid syndrome). 2
Start therapeutic-dose LMWH at 100 units/kg subcutaneously every 12 hours OR unfractionated heparin at 15,000 units subcutaneously every 12 hours immediately. 2
Continue bridging therapy until INR reaches ≥2.0 on two consecutive measurements taken 24 hours apart. 2
For patients with mechanical heart valves specifically, intravenous unfractionated heparin monitored to aPTT of 1.5-2.0 is safer than subcutaneous options if hospitalization is feasible. 2
Acenocoumarol Restart Protocol
Resume acenocoumarol at 50-75% of the pre-interruption maintenance dose to avoid overshooting the target and causing supratherapeutic anticoagulation. 1
Do not use a loading dose, as this increases hemorrhagic risk without providing faster thromboembolic protection when bridging anticoagulation is already in place. 1
Acenocoumarol has a shorter half-life than warfarin (8-11 hours vs 36-42 hours), meaning INR will respond more rapidly to dose changes and requires closer monitoring. 3, 4
Monitoring Schedule
Check INR daily until it reaches 2.0, then continue checking daily until therapeutic range (2.5-3.5 for target INR 3.0) is achieved on two consecutive days. 2
Once stable in therapeutic range, check INR twice weekly for 2 weeks, then weekly for 1 month, then every 2-4 weeks depending on stability. 2
Acenocoumarol requires more frequent monitoring than warfarin due to its shorter half-life and greater INR variability. 4, 5
Target INR Range Considerations
For indications requiring a target INR of 3.0, the therapeutic range is typically 2.5-3.5 (e.g., mechanical mitral valve, caged-ball or tilting-disc valves, recurrent systemic embolism despite therapeutic anticoagulation). 2
The risk of major bleeding rises exponentially when INR exceeds 4.5, so careful dose titration is essential. 2
Critical Pitfalls to Avoid
Never restart at the full previous dose after a 3-day interruption, as acenocoumarol's pharmacokinetics make patients more sensitive to reloading, increasing risk of supratherapeutic INR. 1, 6
Do not delay bridging anticoagulation in high-risk patients—the risk of thromboembolism during the 2-3 days it takes to reach therapeutic INR is substantial (2.1-4.8% within 30 days for mechanical valves and high-risk atrial fibrillation). 2
Avoid subcutaneous LMWH without anti-Xa monitoring in patients with renal failure or obesity, as dosing may be inadequate. 2
Do not use vitamin K to accelerate INR rise, as it paradoxically delays achieving therapeutic anticoagulation and can cause warfarin resistance. 3
Special Considerations for Acenocoumarol
Acenocoumarol shows greater INR instability than warfarin, with patients experiencing INR ≥6 at a rate of 0.3 visits/patient/year versus 0.07 with warfarin. 4
If anticoagulation control remains unstable after 3 months (>50% of INR values out of range), consider switching to warfarin, which improves time in therapeutic range from 40% to 60%. 5
Elderly patients require approximately 20% lower doses of acenocoumarol than younger patients due to increased bleeding risk. 2, 1