Warfarin Drug Interactions — MFDS Part 1 MCQ

Instant feedback + full explanation. One question, done properly.

ModeratePharmacologyWarfarin Drug InteractionsMFDS Part 1

Which drug commonly prescribed in dental practice is recognised to potentiate warfarin by reducing its hepatic catabolism, thereby potentially increasing the INR and risk of haemorrhage?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Metronidazole

Metronidazole is correct. The UK SmPC states it may increase the anticoagulant effect of warfarin by decreasing its hepatic catabolism, prolonging prothrombin time and increasing haemorrhage risk. If co-prescription is unavoidable, SDCEP advises informing the GP or anticoagulation service so increased INR monitoring can be arranged. Amoxicillin has occasionally been associated with a raised INR, but this is a sporadic, less predictable antibiotic-associated effect rather than the specified hepatic metabolic interaction. Prolonged regular paracetamol can potentiate warfarin, but standard short-term dosing is the preferred dental analgesic in warfarinised patients. Ibuprofen increases bleeding risk mainly via antiplatelet and gastrointestinal effects and should generally be avoided with warfarin, but a single dose does not characteristically raise the INR through hepatic inhibition. Chlorhexidine mouthwash has no clinically relevant systemic interaction with warfarin.

Reference: electronic Medicines Compendium (emc), Metronidazole 500 mg/100 ml Intravenous Infusion, Summary of Product Characteristics, section 4.5 Interactions (warfarin: decreased liver catabolism). https://www.medicines.org.uk/emc/product/1842/smpc