Which medication is a directly acting skeletal muscle relaxant used to treat malignant hyperthermia?

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

Answer: (B)

Malignant hyperthermia is driven by uncontrolled calcium release from the skeletal muscle’s sarcoplasmic reticulum, which fuels a dangerous hypermetabolic state. The drug that directly counters this by blocking calcium release is dantrolene. It acts on the ryanodine receptor in the sarcoplasmic reticulum to reduce cytosolic calcium, which lowers muscle contraction, decreases heat production, and helps reverse the metabolic crisis. Other muscle relaxants like cyclobenzaprine, methocarbamol, and baclofen work through the central nervous system to reduce muscle tone or spasticity, not by interrupting calcium release in muscle cells, so they do not address malignant hyperthermia.