Studies on the interaction of steroidal neuromuscular blocking drugs with cardiac muscarinic receptors.

Interaction of the steroidal neuromuscular blocking drugs pancuronium, pipecuronium, rocuronium and vecuronium with cardiac muscarinic receptors in rat hearts was investigated in vitro by a tritiated N-methyl hyoscine binding assay. We showed an interaction with cardiac muscarinic receptors with a rank order of potency pancuronium > vecuronium > pipecuronium > rocuronium and demonstrated complex binding characteristics for pancuronium, vecuronium and rocuronium, with "Hill coefficient" of less than unity. We conclude that the haemodynamic differences seen during the use of these neuromuscular blocking drugs may be a result of their interactions with cardiac M2 muscarinic receptors.