Drug Interactions Dentistry — MFDS Part 1 MCQ

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HardHuman DiseaseDrug Interactions DentistryMFDS Part 1

A dental practitioner has confirmed that erythromycin is otherwise clinically indicated. Which concurrent lipid-lowering medicine makes erythromycin contraindicated, necessitating selection of an alternative antibacterial or liaison with the patient's prescriber if temporary interruption of treatment is being considered?

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Correct answer: E — Simvastatin 40 mg at night

The correct answer is E, simvastatin. Erythromycin inhibits CYP3A4, through which simvastatin is extensively metabolised. Concomitant administration can substantially increase simvastatin exposure and the risk of myopathy and rhabdomyolysis; UK SmPCs therefore classify the combination as contraindicated. If erythromycin is unavoidable, simvastatin must be suspended during the course and an alternative statin considered. A dentist should not independently alter long-term lipid-lowering treatment, so an alternative antibacterial should be selected or the patient's prescriber consulted. Pravastatin, rosuvastatin, ezetimibe and fenofibrate are not listed by the cited erythromycin SmPC as contraindicated concomitant medicines and do not represent the specific CYP3A4 interaction tested.

Reference: Electronic Medicines Compendium. Simvastatin 20 mg film-coated tablets, Summary of Product Characteristics, sections 4.3–4.5; revised 20 March 2026. https://www.medicines.org.uk/emc/product/10666/smpc