Anaes · Neuromuscular blockade & reversal

Atracurium, cisatracurium and mivacurium

Also known as Benzylisoquinoline non-depolarising neuromuscular blockers · Organ-independent muscle relaxants · Hofmann-elimination relaxants

Atracurium, cisatracurium and mivacurium are the benzylisoquinoline non-depolarising neuromuscular blockers, competitive antagonists at the postsynaptic nicotinic (muscle-type) acetylcholine receptor that displace acetylcholine without activating the receptor, producing flaccid paralysis without depolarisation or fasciculation (Radkowski, 2026). Atracurium and cisatracurium are defined by ORGAN-INDEPENDENT elimination — Hofmann elimination (a non-enzymatic, pH- and temperature-dependent spontaneous degradation) plus ester hydrolysis by non-specific plasma esterases — so they are preferred in hepatic and renal failure and for prolonged intensive-care infusion, with the laudanosine metabolite (which crosses the blood-brain barrier and causes cerebral excitation and seizures at high concentrations) as the principal concern (Radkowski, 2025; 2026). Both atracurium and mivacurium release histamine on rapid bolus, but cisatracurium — a stereoisomer (the 1R-cis, 1R-prime-cis isomer) with NEGLIGIBLE histamine release and greater potency (so a lower dose and less laudanosine) — has largely replaced atracurium for cardiac surgery and intensive care (Roy, 2025; He, 2026). Mivacurium is the shortest-acting non-depolariser and is metabolised by plasma butyrylcholinesterase (the same enzyme as suxamethonium), so it is markedly prolonged in butyrylcholinesterase deficiency (Kempff-Andersen, 2026; Snak de Souza, 2026). The class is reversed by neostigmine and NOT by sugammadex (which encapsulates only the aminosteroids rocuronium and vecuronium), and anaphylaxis is a class risk (Zofia Lisiecka, 2026).