Abstract
Mivacurium is a benzylisoquinolone, choline-like, non-depolarizing muscle relaxant. Its onset of action is similar to that of atracurium but its duration of action is shorter (approximately 10–15 minutes). Mivacurium is metabolized by plasma cholinesterases at approximately 70% of the rate of metabolism of suxamethonium1. Deficiency or abnormality of plasma cholinesterase may cause the duration of action of both suxamethonium2,3 and mivacurium2,4,5,6 to be greatly prolonged. We describe a case of prolonged mivacurium paralysis after day surgery. Laboratory investigations showed a genetic tendency toward abnormal cholinesterase levels, but markedly depressed cholinesterase activity was suggestive of additional acquired causes. This patient had a history of liver disease, malnutrition and anticholinesterase use, which we believe were the most significant factors involved.