Dantrolene Mechanism — FRCA Primary MCQ

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ModeratePharmacology - General PrinciplesDantrolene MechanismFRCA Primary

Which direct action of dantrolene in skeletal muscle is principally responsible for its therapeutic effect during a malignant hyperthermia crisis?

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Correct answer: C — Suppressing calcium release from the sarcoplasmic reticulum by binding to RYR1

Explanation lettering: B = shown as A · C = shown as B · A = shown as C · E = shown as D · D = shown as E

Dantrolene is a directly acting skeletal-muscle relaxant. It binds ryanodine receptor type 1 (RYR1) and suppresses calcium release from the sarcoplasmic reticulum. This reduces the excessive myoplasmic calcium concentration that drives sustained contraction and accelerated metabolism during malignant hyperthermia. It does not primarily increase calcium sequestration through SERCA (B), block muscle action potentials through sodium channels (C), or antagonise postsynaptic nicotinic receptors (D); neuromuscular transmission and the excitable surface membrane are not its principal targets. L-type calcium-channel blockade in vascular smooth muscle (E) is also not its therapeutic mechanism and would not directly control the skeletal-muscle hypermetabolic process.

Reference: Electronic Medicines Compendium, Agilus 120 mg powder for solution for injection, Summary of Product Characteristics, section 5.1 Pharmacodynamic properties, revised 2025. https://www.medicines.org.uk/emc/product/15912/smpc