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Drug-Induced Myasthenic Crisis — RACP Adult Medicine MCQ

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ModerateNeurologyDrug-Induced Myasthenic CrisisRACP Adult Medicine

A 30-year-old woman with known myasthenia gravis (anti-AChR antibody positive) presents with increasing dysphagia, diplopia, and respiratory distress. FVC is 15 mL/kg (normal >60). She was started on ciprofloxacin 2 days ago for a UTI. What is the most likely precipitant?

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Correct answer: A — Drug-exacerbated myasthenic crisis

Myasthenic crisis (respiratory failure requiring ventilation) precipitated by fluoroquinolone antibiotics (ciprofloxacin, levofloxacin) is well-documented. Fluoroquinolones impair neuromuscular transmission. Other exacerbating drugs include aminoglycosides, beta-blockers, magnesium, and D-penicillamine. FVC <20 mL/kg or <1 L warrants ICU admission. Treatment: plasma exchange or IVIG, and cease the offending drug.

Reference: eTG Neurology – 2024 – Myasthenia Gravis; AMH 2025