Acenocoumarol Dosing Regimen and INR-Based Adjustments
The initial dosing regimen for acenocoumarol should follow age-based guidelines, with maintenance dose adjustments based on a structured INR algorithm targeting a therapeutic range of 2.0-3.0 for most indications. 1
Initial Dosing
Initial dosing of acenocoumarol should be age-stratified as follows:
- Adults: Standard initial dose is typically 2-4 mg once daily for 1-2 days, followed by dose adjustment based on INR response
- Pediatric patients:
- 2 months to 1 year: 0.20 mg/kg once daily
1-5 years: 0.09 mg/kg once daily
- 6-10 years: 0.07 mg/kg once daily
- 11-18 years: 0.06 mg/kg once daily 2
Maintenance Dosing Algorithm
After initiation, adjust acenocoumarol doses according to this INR-based algorithm:
| INR Value | Dose Adjustment |
|---|---|
| 1.1-1.4 | Increase dose by 20% |
| 1.5-1.9 | Increase dose by 10% |
| 2.0-3.0 | No change (maintain current dose) |
| 3.1-3.5 | Decrease dose by 10% |
| >3.5 | Hold until INR <3.5, then restart at 20% lower dose |
| >10 | Hold medication and administer oral vitamin K |
INR Monitoring Schedule
- Initial phase: Check INR every 2-3 days until stable
- After dose changes: Monitor more frequently until stability is achieved
- Stable patients: Monitor every 4-6 weeks 1
Important Clinical Considerations
Dosing Precision
- Aim for uniform daily dosing when possible
- Patients taking uneven doses (e.g., alternating between different daily doses) show significant fluctuations in anticoagulation levels 3
- The INR value is significantly influenced by the dose taken 2 days before measurement 3
Elderly Patients
- Older patients (≥80 years) typically require lower acenocoumarol doses
- More precise dosing with smaller increments (0.5 mg) may slightly improve time in therapeutic range compared to conventional dosing with 1.0 mg increments 4
Bleeding Management
- For INR >10 without bleeding: Hold acenocoumarol and administer oral vitamin K
- For major bleeding at any INR level: Reverse anticoagulation rapidly with IV vitamin K plus activated prothrombin concentrate 2
- Caution with vitamin K dosing: Low-dose oral vitamin K (1 mg) for acenocoumarol reversal may cause excessive over-reversal of INR 5
Medication Interactions
- Be vigilant for medications that may interact with acenocoumarol
- NSAIDs should be avoided due to increased bleeding risk 1
- Consider genetic factors that may influence response (VKORC1 and CALU polymorphisms can significantly affect dose requirements) 6
Pitfalls to Avoid
- Don't make dose adjustments based on a single out-of-range INR if the patient was previously stable
- Avoid large dose changes (most adjustments should alter weekly dose by 5-20%)
- Don't overlook dietary changes that affect vitamin K intake
- For patients with previously stable INRs and a single reading 0.5 below or above therapeutic range, continue current dose and retest within 1-2 weeks rather than making immediate adjustments 1
By following this structured approach to acenocoumarol dosing and monitoring, clinicians can optimize anticoagulation efficacy while minimizing bleeding risks and maintaining patients within the therapeutic INR range.