Myasthenia Gravis Drug Caution — MFDS Part 1 MCQ

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HardHuman DiseaseMyasthenia Gravis Drug CautionMFDS Part 1

A patient with stable generalised myasthenia gravis controlled with pyridostigmine requires dental treatment. They have no relevant drug allergies or other medical contraindications. Which proposed medicine should be avoided because it can further impair neuromuscular transmission and precipitate severe muscle weakness or respiratory compromise?

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Correct answer: C — Gentamicin

Gentamicin is an aminoglycoside and should be avoided in myasthenia gravis. Aminoglycosides can impair neuromuscular transmission, aggravating skeletal-muscle weakness and potentially causing neuromuscular blockade, respiratory paralysis or a myasthenic deterioration. Current UK gentamicin and amikacin SmPCs specifically contraindicate their use in myasthenia gravis. Amoxicillin does not share this neuromuscular-blocking effect. Ibuprofen and paracetamol are not specifically contraindicated by myasthenia gravis, although their usual patient-specific contraindications must still be considered. Lidocaine is an amide local anaesthetic and is not an absolute contraindication in a stable patient; the minimum effective dose and appropriate clinical monitoring should be used. Thus, gentamicin is the uniquely contraindicated option.

Reference: Electronic Medicines Compendium. Gentamicin 40 mg/ml Solution for Injection/Infusion, Summary of Product Characteristics, sections 4.3–4.4. Updated 2025. https://www.medicines.org.uk/emc/product/12877/smpc