Erythromycin Warfarin INR Recheck — ORE Part 1 MCQ

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HardPharmacology & TherapeuticsErythromycin Warfarin INR RecheckORE Part 1

A patient taking warfarin attends for a planned simple extraction. Their INR was 2.5 when checked 48 hours ago. They started erythromycin for a chest infection on the same day. What is the most appropriate management?

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Correct answer: C — Defer treatment and arrange an INR check within 24 hours

Explanation lettering: D = shown as A · A = shown as C · C = shown as D

A is correct. Erythromycin can increase the anticoagulant effect of warfarin, and infection itself may also alter coagulation or drug metabolism. Although an INR from within 72 hours can be accepted for a patient with stable anticoagulation, SDCEP states that it should be repeated within 24 hours when there is reason to think it no longer represents the current INR. The result of 2.5 preceded, or coincided with, initiation of erythromycin, so it cannot be relied on. B and C wrongly treat the earlier INR as current; local measures do not compensate for an unknown INR. D is inappropriate because the dentist should not stop treatment prescribed for a chest infection. E unnecessarily interrupts warfarin and exposes the patient to thromboembolic risk.

Reference: Scottish Dental Clinical Effectiveness Programme. Management of Dental Patients Taking Anticoagulants or Antiplatelet Drugs, clinical practice advice: Warfarin or another vitamin K antagonist, 2022. https://www.sdcep.org.uk/media/efmfgy44/sdcep-anticoagulants-guidance.pdf