Management of Acenocoumarol After 2 Days of 5 mg Daily Dosing
Continue acenocoumarol at 5 mg daily on day 3 and beyond, as this dose exceeds the standard 3 mg maintenance dose and requires 4-8 days to achieve therapeutic effect—an INR check on day 2 is premature and does not reflect treatment failure. 1
Understanding Acenocoumarol Pharmacokinetics
The critical issue here is timing, not dosing inadequacy:
- Acenocoumarol has a plasma half-life of only 9 hours (compared to warfarin's 42 hours), requiring 2-3 days for partial anticoagulant effect and 4-8 days for full therapeutic effect 2, 1
- After only 2 days of therapy, insufficient time has elapsed to deplete existing vitamin K-dependent clotting factors (II, VII, IX, X), making any INR measurement at this point clinically meaningless 2, 1
- The standard starting dose for acenocoumarol is 3 mg daily, and you are already administering 5 mg daily—well above the expected maintenance dose 2, 1
Appropriate Monitoring Schedule
Do not check INR until day 5 at the earliest:
- INR monitoring should be performed daily starting when therapeutic range is expected (typically day 5-7), then twice or three times weekly during the first 2 weeks once therapeutic range (2.0-3.0) is achieved 2
- Patients typically achieve therapeutic INR within 5-7 days when started on appropriate maintenance doses 1
- Checking INR prematurely (day 2-3) leads to inappropriate dose escalation and subsequent supratherapeutic INR with bleeding risk 3
Critical Safety Considerations
Ensure overlap with parenteral anticoagulation:
- Continue heparin or low molecular weight heparin for at least 5 days AND until INR is 2.0-3.0 for two consecutive days 2, 1
- Heparin should not be discontinued based on a single INR value, even if therapeutic 2
Common Pitfalls to Avoid
Do not increase the acenocoumarol dose based on early INR values:
- Loading doses of oral anticoagulants do not achieve therapeutic INR more rapidly than maintenance dosing and significantly increase bleeding risk 2, 1
- One case report documented massive hematuria and INR of 10.5 on day 5 in a patient started on 4 mg daily for 2 days then 3 mg daily—lower than your current 5 mg regimen—due to genetic hypersensitivity 3
Be aware of dose-response timing:
- Each INR value correlates most strongly with the acenocoumarol dose administered 2 days prior, not the current day's dose 4
- Patients taking uneven daily doses (e.g., alternating 2 mg and 4 mg) show significant INR fluctuations compared to uniform daily dosing 4
When to Suspect Problems
Consider dose reduction or genetic testing if by day 7-10: