Effects of succinylcholine on the recovery of block produced by mivacurium in rats

This study investigates the effects of succinylcholine on the recovery of neuromuscular blockade produced by mivacurium in rats. In 48 anesthetized animals, the sciatic nerve was prepared and stimulated, and twitches of the flexor digitorum longus muscle were recorded. Animals were randomly divided into four groups (n = 12 each): bolus dose of succinylcholine 0.1 mg/kg (GroupSch), bolus dose of mivacurium 0.15 mg/kg (GroupMiv), bolus dose of mivacurium 0.15 mg/kg, followed by succinylcholine 0.1 mg/kg at 25% neuromuscular recovery from mivacurium (Group-MivSch(25)), or bolus dose of mivacurium 0.15 mg/kg, followed by succinylcholine 0.1 mg/kg at 75% neuromuscular recovery from mivacurium (GroupMivSch(75)). Onset times of neuromuscular block following succinylcholine in mivacurium-treated groups were comparable and significantly shorter than in GroupSch (p < 0.001). Duration of action of succinylcholine was more prolonged when it was given in the presence of deeper neuromuscular block induced by mivacurium (p < 0.001 in GroupMivSch(25) and p < 0.01 in GroupMivSch(75)). Our results suggest that, in rats, mivacurium administration has a significant potentiating effect on a subsequent succinylcholine-induced neuromuscular block.