The pharmacodynamics of mivacurium preceded by atracurium or cisatracurium in children.

Unlabelled: We evaluated whether mivacurium maintains its short duration of effect when preceded by atracurium or cisatracurium in 45 children during propofol/alfentanil/N2O/O2 anesthesia. Neuromuscular response was recorded by using an adductor pollicis electromyogram (EMG). Children were randomized to receive two doses of atracurium (350 micrograms/kg and 70 micrograms/kg in Group AM), cisatracurium (64 micrograms/kg and 10 micrograms/kg in Group CM), or mivacurium (200 micrograms/kg and 100 micrograms/kg in Group MM), followed by a final dose of mivacurium 100 micrograms/kg. The second and third doses of the muscle relaxants were administered at 25% EMG recovery. After the final dose of mivacurium, the times to 95% of EMG recovery in groups AM, CM, and MM were (median with 10-90 percentile range) 33.0 (28.0-40.0) min, 30.7 (26.0-40.3) min, and 10.3 (8.0-14.0) min, respectively (P < 0.0001). The recovery times to a train-of-four ratio of 0.70 were 30.3 (24.7-37.0) min, 28.0 (24.7-37.7) min, and 10.3 (8.0-13.7) min for groups AM, CM, and MM, respectively (P < 0.0001). Thus, the duration of effect of mivacurium was prolonged by 200% if preceded by either atracurium or cisatracurium.

Implications: We compared the pharmacodynamics of mivacurium given alone or preceded by atracurium or cisatracurium in children. The duration of effects of mivacurium was prolonged by 200% if preceded by either atracurium or cisatracurium. This implies that mivacurium has a short duration of effect only when given as a single relaxant.