Management of Acenocoumarol After Erratic INR Control
Continue acenocoumarol 4.5 mg daily and check INR on day 3 as planned, then adjust based on that result rather than making further changes now. You've already given 2 days of 5 mg after the dramatic overcorrection from omitting 3 doses, and the INR of 0.7 indicates you overshot the reversal—now you need to find the middle ground between your original 4 mg (which was slightly subtherapeutic) and the 5 mg (which caused supratherapeutic levels).
Rationale for Current Dosing Strategy
The 4 mg daily dose achieved an INR of 2.5, which is only 0.5 below your target of 3.0—this represents stable, near-therapeutic anticoagulation that likely required only minor adjustment 1, 2
Your dose escalation to 5 mg daily (a 25% increase) was excessive for an INR deviation of only 0.5 below target, leading to the INR of 4.7 1
Omitting 3 consecutive doses caused catastrophic overcorrection to INR 0.7, demonstrating acenocoumarol's short half-life and the danger of holding multiple doses 3
After 2 days of 5 mg following the INR of 0.7, a dose of 4.5 mg daily represents a reasonable middle ground between the dose that was slightly low (4 mg) and the dose that was too high (5 mg) 1
Day 3 INR Interpretation and Next Steps
If INR is 2.0-3.5 on Day 3:
- Continue 4.5 mg daily and recheck INR in 3-5 days to confirm stability 1
- Once two consecutive INRs are therapeutic, extend monitoring to weekly, then monthly 1
If INR is 1.5-1.9 on Day 3:
- Increase to 5 mg daily and recheck in 3-4 days 1, 2
- Do not use heparin bridging for a single subtherapeutic INR—evidence shows no benefit and increased bleeding risk 1, 2
If INR is <1.5 on Day 3:
- Increase to 5 mg daily, consider adding one loading dose of 6-7 mg, then continue 5 mg daily 1
- Recheck INR in 2-3 days 1
If INR is 3.6-4.5 on Day 3:
- Reduce to 4 mg daily and recheck in 3-5 days 1
If INR is >4.5 on Day 3:
- Hold one dose, then resume at 4 mg daily 1, 3
- Avoid vitamin K—a study showed 1 mg oral vitamin K in acenocoumarol patients caused excessive overcorrection with 36.6% becoming subtherapeutic 3
Critical Lessons from This Case
For INR deviations of ≤0.5 from target, guidelines recommend continuing the same dose rather than making adjustments 1, 2
When dose adjustment is needed for minor deviations, increase or decrease by 5-15% (not 25%) to avoid the dramatic swings you experienced 1
Never omit more than 1-2 doses of acenocoumarol even for elevated INR, as its short half-life (8-11 hours) makes overcorrection likely 3
Acenocoumarol has greater intraindividual variability than warfarin—a study showed patients with unstable acenocoumarol control improved when switched to warfarin, with time in therapeutic range increasing from 40% to 60% 4
Monitoring Frequency Going Forward
- Check INR every 2-3 days until you achieve two consecutive therapeutic values 1
- Then check 2-3 times weekly for 1-2 weeks 1
- Then weekly for 1 month 1
- Then monthly once stable (defined as three consecutive INRs between 2.0-3.5) 1
Common Pitfalls to Avoid
Avoid overreacting to single out-of-range INR values—evidence shows immediate dose changes for minor deviations don't improve outcomes 1, 2
Don't hold multiple doses for moderately elevated INR—omitting even one dose of acenocoumarol can drop INR significantly given its short half-life 3
Avoid vitamin K for acenocoumarol reversal unless INR >10 or bleeding present—it causes excessive overcorrection in 37% of patients 3
Screen for new medications, dietary changes, or illness that could explain INR instability—antibiotics, NSAIDs, acetaminophen >9 grams/week, and alcohol all significantly affect INR 1