Management of Subtherapeutic INR After Sintrom (Acenocoumarol) Interruption
Continue Sintrom at 5 mg daily and recheck INR in 3-5 days, as you have already appropriately resumed the patient's baseline dose after the 3-day hold for the elevated INR of 4.7.
Current Situation Assessment
Your management so far has been appropriate:
You correctly held Sintrom for 3 days when INR was 4.7 1. The American College of Chest Physicians recommends withholding warfarin/acenocoumarol for INRs between 4.0-5.0 without bleeding 1.
You appropriately restarted at the baseline dose of 5 mg daily after the hold, which you've now given for 2 consecutive days 2.
Recommended Next Steps
Continue the current 5 mg daily dose and monitor closely:
Recheck INR in 3-5 days to assess response 1. More frequent monitoring is indicated after dose interruptions until stability is re-established 1.
Do NOT increase the dose yet based on a single subtherapeutic INR reading 2. The American College of Chest Physicians suggests against changing doses for a single out-of-range INR value (Grade 2C recommendation) 2.
Do NOT use bridging anticoagulation (such as LMWH or heparin) for a single subtherapeutic INR in stable patients 2. Studies show no significant difference in thromboembolic events between bridged and non-bridged patients with single low INRs 2.
Key Considerations Specific to Acenocoumarol (Sintrom)
Acenocoumarol has unique pharmacokinetics that affect your management:
Acenocoumarol has a shorter half-life than warfarin (8-11 hours vs 36-42 hours), meaning INR fluctuations occur more rapidly 3, 4.
Patients on acenocoumarol experience subtherapeutic INRs twice as often as those on warfarin (hazard ratio 2.1) 3.
Vitamin K is less effective for acenocoumarol-induced coagulopathy compared to warfarin 5, 6. This is relevant because your patient may have residual vitamin K effect if any was given during the elevated INR management.
When to Consider Dose Adjustment
Only adjust the dose if:
The INR remains subtherapeutic on repeat testing in 3-5 days 2. A single out-of-range value does not warrant dose changes 2.
If dose adjustment becomes necessary, increase by approximately 5-15% of the weekly total dose (approximately 0.5-1 mg increase in daily dose) 1.
Monitoring Strategy Going Forward
Establish more frequent monitoring temporarily:
Check INR every 3-5 days until two consecutive therapeutic values are obtained 1.
Then extend to weekly monitoring for 2-3 weeks if stable 2.
Return to routine monitoring intervals (typically every 4 weeks) once stability is confirmed 2.
Common Pitfalls to Avoid
Do not make these errors:
Avoid premature dose escalation based on the first subtherapeutic INR after restarting 2. This leads to INR overshooting and cycling between high and low values.
Do not use bridging therapy unless the patient has very high thrombotic risk (mechanical mitral valve, recent thromboembolism within 3 months, or multiple risk factors) 2.
Avoid checking INR too soon (within 24-48 hours of restarting) as acenocoumarol needs 2-3 days to show full effect 3.
Risk Stratification for Thromboembolism
Assess if your patient has high-risk features that might warrant closer monitoring:
- Mechanical mitral valve or older-generation mechanical aortic valve 2
- Atrial fibrillation with additional risk factors 2
- Recent thromboembolism (within 3 months) 2
- Left ventricular dysfunction (LVEF <30%) 2
If none of these high-risk features are present, the risk of thromboembolism from a brief period of subtherapeutic INR is very low (0.3-0.4%) 2, and your current conservative approach is appropriate.