Comparative neuromuscular blocking potency of pipecuronium and pancuronium

The effects of pipecuronium bromide (Pi.) and pancuronium bromide (Pa.) on the contractile response of rat-phrenic nerve diaphragm and frog's musculus rectus abdominis preparation were studied. Pi. and Pa. were found to have a dose-dependent reduction in the contractile response of the tested preparation. Trials were made to estimate the potency of Pi. in a comparison with Pa. In this respect Pi. exhibited a more potent effect than Pa. The duration of action is about twice as long as that of Pa. in equieffective doses. Neostigmine rapidly and completely antagonises the neuromuscular blockade caused by Pi. and Pa.