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Magnesium and neuromuscular blockade — FRCA Primary MCQ

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HardPharmacologyMagnesium and neuromuscular blockadeFRCA Primary

A patient with severe pre-eclampsia has magnesium sulphate therapy and requires general anaesthesia. After rocuronium, neuromuscular recovery is slower than expected. What is the most likely explanation?

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Correct answer: A — Magnesium reduces acetylcholine release at the neuromuscular junction

Magnesium potentiates neuromuscular blockade partly by reducing presynaptic acetylcholine release and decreasing muscle membrane excitability. It does not increase plasma cholinesterase activity or antagonise non-depolarising block. Rocuronium clearance is not increased by magnesium. The clinical pearl is to monitor neuromuscular function quantitatively in patients receiving magnesium.

Reference: RCoA Primary FRCA Syllabus 2026; Peck, Hill & Williams Pharmacology for Anaesthesia