Onset time and duration of action for atracurium, Org NC45 and pancuronium

Speed of onset, maximum block, duration of action and 10-25% recovery time for atracurium, Org NC 45 and pancuronium were determined using equipotent doses: 330 micrograms kg-1, 66 micrograms kg-1 and 75 micrograms kg-1 respectively. Vein-to-muscle and artery-to-muscle onset times were measured by use of simultaneous recordings. Mean speeds of onset to 95% twitch depression were: atracurium 2.7 min, Org NC 45 2.8 min and pancuronium 3.6 min. The median value of maximum neuromuscular block exceeded 98.5% for all drugs and the mean durations of action to 25% recovery of control twitch height were: atracurium 27.6 min, Org NC 45 21.9 min and pancuronium 45.1 min. The differences were statistically significant. The recovery period from 10% to 25% twitch response was considerably longer for pancuronium than for the other drugs, which did not differ significantly from each other. We were unable to validate the artery-to-muscle technique in the determination of onset time.