Comparison of recovery index of rocuronium or vecuronium with simultaneously administered pancuronium in the isolated forearm

A series of isolated forearm experiments is described in which rocuronium or vecuronium were injected into one arm, and pancuronium injected simultaneously into the contralateral arm. The time for 25%-75% twitch recovery (recovery index) was recorded in both arms. The recovery indices of rocuronium and vecuronium were similar, but that of pancuronium significantly longer. Because the recovery indices compared in any one experiment occurred in the presence of identical background plasma concentration, the differences observed in recovery index between pancuronium and either rocuronium or vecuronium are due to different rates of dissociation from the effect compartment at the neuromuscular junction.