Mivacurium is a benzylisoquinolinium diester. The drug is a nondepolarizing relaxant which is hydrolysed by plasma cholinesterase at 70-88% of the rate of suxamethonium. Enzymatic hydrolysis gives the drug its short duration of action. The length of paralysis is about 2-2.5 times that of suxamethonium and one-half to one-third that of the intermediate-acting nondepolarizers. The development of mivacurium represents a collaboration between industrial pharmacologists and chemists at Burroughs Wellcome Co. (USA) and investigators at the Massachusetts General Hospital, Boston, MA, USA.