Metronidazole Drug Interactions — MFDS Part 1 MCQ

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EasyPharmacologyMetronidazole Drug InteractionsMFDS Part 1

A dentist prescribes oral metronidazole for an acute dental infection. Which substance should the patient be advised to avoid because concomitant use may cause a disulfiram-like reaction?

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Correct answer: D — Alcohol

Alcohol is the correct answer. UK prescribing information advises patients not to consume alcohol during systemic metronidazole treatment or for at least 48 hours afterwards because the combination may produce a disulfiram-like reaction. Possible features include nausea, vomiting, abdominal pain, flushing, headache and palpitations. The precise biochemical mechanism is not sufficiently established to state categorically that metronidazole directly inhibits aldehyde dehydrogenase, so that claim should be avoided. Grapefruit juice, dairy products, coffee and tobacco are not subject to an equivalent standard avoidance instruction with metronidazole; NHS advice states that, apart from alcohol, patients can eat and drink normally.

Reference: Aurobindo Pharma–Milpharm Ltd, Metronidazole 400 mg Tablets, Summary of Product Characteristics, section 4.5 Interactions, updated 2025. https://www.medicines.org.uk/emc/product/12817/smpc