The (1R,1'R,2R,2'R)-diastereoisomer of atracurium besylate. Commercial preparations of atracurium are mixtures of 10 stereoisomers, of which cisatracurium generally constitutes about 15%. Cisatracurium besylate is about 3 times more potent than the mixture of atracurium isomers as a neuromuscular blocking agent, and is used as a muscle relaxant for endotracheal intubation, to aid controlled ventilation, and in general anaesthesia.