clinically tested agents, BW785U77 and BWA444U, which were discontinued from further clinical development. Mivacurium did not exhibit the ultra-short duration of action seen with BW785U; whereas, BW A444U produced an intermediate duration of action. Mivacurium is a biodegradable neuromuscular blocking agent owing to its degradation by plasma cholinesterases - the esterases rapidly hydrolyze one ester moiety initially resulting in a two mono-quaternary metabolites of which one still has an intact ester moiety. The second ester is metabolized much more slowly, although the lack of a bis-quaternary structure effectively terminates the neuromuscular blocking action. References Nicotinic antagonists Norsalsolinol ethers Chlorides Carboxylate esters