RECOVERY FROM PANCURONIUM AND VECURONIUM ADMINISTERED SIMULTANEOUSLY IN THE ISOLATED FOREARM AND THE EFFECT ON RECOVERY FOLLOWING ADMINISTRATION AFTER CROSS-OVER OF DRUGS

If recovery of neuromuscular block in the isolated arm is determined b y biophase binding, then a significant amount of drug will still be pr esent in the biophase at 50% recovery of twitch response. To test this hypothesis we administered pancuronium at 50% recovery from vecuroniu m block and vecuronium at 50% recovery from pancuronium block in the i solated forearms of volunteers. To ensure that any effect of drug rele ased into the plasma did not affect the results, both experiments were performed simultaneously, one in each forearm, of each volunteer. Con trol experiments were performed to determine the effect of subsequent injections of the same drug at 50% recovery and of subsequent injectio ns of the alternative drug (i.e., vecuronium following pancuronium and pancuronium following vecuronium) at 100% recovery of the twitch resp onse. Prior administration of vecuronium significantly shortened the r ecovery from subsequent pancuronium when administered at 50% recovery, but not 100% recovery, and pancuronium significantly increased the re covery rate of vecuronium when given at 50% recovery but not 100% reco very. These findings support the concept of biophase binding of nondep olarizing neuromuscular blocking drugs.