Priming of pancuronium with magnesium.

Magnesium inhibits the release of acetylcholine from the motor nerve terminal and thus potentiates the action of the non-depolarizing neuromuscular blocking drugs. We have examined the possibility that this effect might enhance the speed of onset of non-depolarizing block with pancuronium. Following the administration of pancuronium 100 micrograms kg-1, 95% depression of thumb twitch occurred in 68.3 (SD 25.9) s in magnesium-pretreated subjects and in 73.7 (19.5) s in a group given a priming dose (10 micrograms kg-1) of pancuronium. Tracheal intubation was performed after 97.8 (22.5) s in the magnesium group and in 121.0 (37.5) s in the control group (ns). It is concluded that pretreatment with magnesium does not usefully increase the speed of onset of action of pancuronium.