Influence of "priming" on the potency of non-depolarizing neuromuscular blocking agents

Dose-response curves have been constructed to determine the ED50 and ED95 (doses required to produce a 50% and a 95% block, respectively) following administration of a small "priming" dose of atracurium 50 micrograms kg-1, vecuronium 10 micrograms kg-1 or pancuronium 10 micrograms kg-1. The myoneural blockers were administered subsequently as a single bolus. The results were compared with previously published work on these drugs, in which no priming dose had been administered. The respective ED50 and ED95 values in the primed and control groups were 122 and 126 micrograms kg-1 and 208 and 226 micrograms kg-1, respectively, for atracurium; 26 and 23 micrograms kg-1 and 42 and 39 micrograms kg-1, respectively, for vecuronium; and 31 and 30 micrograms kg-1 and 56 and 60 micrograms kg-1, respectively, for pancuronium. The values showed no significant differences between the respective primed and control groups. Contrary to previous suggestions, our results show no enhancement of blockade when these drugs were administered in divided doses.