Which IV-form muscle relaxant is used to treat skeletal muscle spasms caused by malignant hyperthermia?

• A. Dantrolene
• B. Baclofen
• C. Carisoprodol
• D. Cyclobenzaprine

Answer: (A)

During malignant hyperthermia, an abnormal surge of calcium release from the skeletal muscle’s sarcoplasmic reticulum drives prolonged muscle contraction and a dangerous hypermetabolic state. The IV-form muscle relaxant used to counter this is dantrolene because it directly inhibits calcium release by blocking the ryanodine receptor on the sarcoplasmic reticulum, quickly reducing muscle rigidity and hypermetabolism. This rapid IV administration is essential in an acute MH crisis, and it is given alongside stopping triggering agents, 100% oxygen, cooling, and management of electrolytes and acidosis. Other muscle relaxants like baclofen (for chronic spasticity) or carisoprodol and cyclobenzaprine (for musculoskeletal pain/spasms) do not affect the calcium dysregulation seen in MH and are not appropriate in this emergency.