Dose Adjustment for Sintrom (Acenocoumarol) to Achieve Target INR of 3.0
For a current INR of 1.6 with a target of 3.0, increase your daily Sintrom dose by 20% for the next 4 days, then recheck the INR. 1
Rationale for Dose Adjustment
The current INR of 1.6 falls within the 1.5-1.9 range, which according to the American Society of Hematology/International Society on Thrombosis and Haemostasis guidelines for vitamin K antagonist (VKA) maintenance dosing, requires a 10% dose increase when targeting an INR of 2.0-3.0. 1 However, since your target is specifically 3.0 (the upper end of the therapeutic range), and you are starting from 1.6 (significantly subtherapeutic), a 20% dose increase is more appropriate based on the guideline recommendation for INR 1.1-1.4. 1
Specific Dosing Strategy
Calculate your current weekly dose of Sintrom and increase it by 20% to determine the new daily dose. 1
Administer this increased dose daily for 4 consecutive days, as this timeframe allows acenocoumarol (which has a shorter half-life than warfarin) to reach steady-state effects. 2, 3
Recheck your INR on day 5 (after 4 days of the increased dose) to assess response and make further adjustments if needed. 1
Important Monitoring Considerations
The American College of Chest Physicians emphasizes that for patients with previously stable INRs who present with a single subtherapeutic value, bridging with heparin is not routinely recommended, as retrospective studies show no significant difference in thromboembolic events. 4
Do not make multiple dose adjustments in rapid succession, as this leads to INR instability and overcorrection. 5
Acenocoumarol has a shorter half-life than warfarin, meaning INR can change more rapidly, requiring closer monitoring during dose adjustments. 6, 3
Common Pitfalls to Avoid
Avoid unnecessarily administering bridging therapy for a single subtherapeutic INR, which increases bleeding risk without clear benefit. 4
Do not make large dose adjustments based on a single reading, as this can lead to INR instability and potential overshoot into supratherapeutic ranges. 4, 5
Investigate potential causes of the subtherapeutic INR, including medication changes (particularly antibiotics like amoxicillin which can interact with acenocoumarol), dietary vitamin K intake variations, or compliance issues. 5, 7
Be aware that acenocoumarol use has been associated with two-fold higher risk for instability of anticoagulation control compared to warfarin, so closer monitoring may be warranted. 3
Special Considerations for Higher Risk Patients
For patients with mechanical heart valves, a higher risk of thromboembolism exists with subtherapeutic INRs, but bridging is still not routinely recommended for a single subtherapeutic value. 4
Individual risk assessment may warrant more aggressive management only for patients with recent thromboembolism or very high-risk conditions. 4