How to proceed with acenocoumarol (vitamin K antagonist) dosing after omitting 3 doses due to elevated International Normalized Ratio (INR) of 4.7, resulting in a decreased INR of 0.7?

Management of Acenocoumarol After Overcorrection

Resume acenocoumarol immediately at a reduced dose of approximately 3.5-4 mg daily (20% reduction from your previous stable dose of 4 mg), as the INR of 0.7 indicates complete loss of anticoagulation and places you at significant thromboembolism risk. 1, 2

Immediate Action Required

• Restart acenocoumarol today at 3.5-4 mg daily (approximately 80% of your previous stable dose of 4 mg that maintained INR 2.5) 2
• The INR of 0.7 represents complete loss of anticoagulation protection, creating substantial thrombotic risk that outweighs any residual bleeding concerns from the prior INR of 4.7 1
• Omitting 3 doses was excessive for an INR of 4.7 without bleeding—guidelines recommend omitting only 1-2 doses for INR 5-9 3, 1

Why This Happened

• Acenocoumarol has a shorter half-life than warfarin (8-11 hours vs 36-42 hours), making it more prone to rapid INR fluctuations and overcorrection 4, 5
• Your initial dose increase from 4 mg to 5 mg daily (25% increase) was too aggressive—this likely caused the INR to rise from 2.5 to 4.7 6
• The subsequent omission of 3 doses caused excessive reversal, dropping the INR below therapeutic range 5

Monitoring Protocol

• Recheck INR in 24-48 hours after restarting acenocoumarol to assess response 1, 2
• Continue monitoring every 24-48 hours until INR stabilizes in therapeutic range (2.0-3.0) 2
• Once stable, transition to weekly monitoring for 2-3 weeks, then resume routine monitoring intervals 1

Dosing Strategy Going Forward

• For future dose adjustments with acenocoumarol, make smaller incremental changes (5-10% of weekly dose, not 25%) due to its shorter half-life and greater variability 6
• When your INR was 2.5 on 4 mg daily (target 3.0), a more appropriate adjustment would have been 4.5 mg daily (12.5% increase) rather than 5 mg 6
• If INR becomes elevated again (4.5-9.0) without bleeding, omit only 1 dose and recheck INR, rather than omitting multiple doses 3, 1

Critical Pitfall to Avoid

• Never omit more than 1-2 doses of acenocoumarol for elevated INR without bleeding—its short half-life means the INR drops rapidly, and excessive omission leads to subtherapeutic anticoagulation as you experienced 5
• Research specifically on acenocoumarol shows that even 1 mg oral vitamin K causes excessive overcorrection in 36.6% of patients, demonstrating how sensitive acenocoumarol is to reversal interventions 5
• The absolute daily bleeding risk remains low (<5.5 per 1000 per day) even at INR 4.7, whereas the thromboembolism risk from complete loss of anticoagulation is substantial 4

Special Considerations for Acenocoumarol

• Acenocoumarol requires more frequent monitoring than warfarin due to greater INR variability 6
• Vitamin K is less effective for acenocoumarol overcorrection compared to warfarin, making dose omission the preferred strategy—but you omitted too many doses 4
• Early INR control patterns with acenocoumarol predict future control: your current instability suggests you may need closer monitoring going forward 6