MechanismDepolarizing neuromuscular blocker. Acts as an agonist at nicotinic acetylcholine receptors (nAChR) causing continuous depolarization.
Phase I Block Continuous depolarization of the endplate. Characterized by fasciculations (twitching) followed by flaccid paralysis. Voltage-gated Na+ channels remain inactivated.
Phase II Block With continued exposure, receptors become desensitized. The membrane repolarizes, but stays blocked (resembles non-depolarizing block).
Hyperkalemia Opening of nAChR channels allows K+ efflux.
ContraindicationsBurns and Denervating Injuries (Guillain-Barré, Quadriplegia). These conditions cause upregulation of extra-junctional receptors, leading to massive K+ release and life-threatening arrhythmias.