Cisatracurium besylate (51W89) is a nondepolarizing neuromuscular blocking agent, antagonizing the action of acetylcholine by inhibiting neuromuscular transmission.

Cisatracurium Besylate (51W89) is a neuromuscular-blocking drug or skeletal muscle relaxant in the category of non-depolarizing neuromuscular-blocking drugs, used adjunctively in anesthesia to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation. It is a bisbenzyltetrahydroisoquinolinium agent with an intermediate duration of action. Cisatracurium Besylate (51W89) is one of the ten isomers of the parent molecule, atracurium. Moreover, cisatracurium represents approximately 15% of the atracurium mixture [1, 2].

References:
[1]. Dear, G.J., et al., Identification of urinary and biliary conjugated metabolites of the neuromuscular blocker 51W89 by liquid chromatography/mass spectrometry. Rapid Commun Mass Spectrom, 1995. 9(14): p. 1457-64.
[2]. Serra, C.S. and A.C. Oliveira, Cisatracurium: myographical and electrophysiological studies in the isolated rat muscle. Fundam Clin Pharmacol, 2006. 20(3): p. 291-8.