Clinical pharmacology of doxacurium chloride (BW A938U) in children

The neuromuscular effects of doxacurium were studied in 26 children during halothane-nitrous oxide-oxygen anesthesia. Neuromuscular blockade was measured using electromyographic activity of the adductor pollicis muscle after supramaximal stimulation of the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. To estimate the cumulative dose-response relation, nine patients received incremental doses of doxacurium (2.5-10 micrograms/kg); nine patients received 27.5 micrograms/kg (the estimated ED95); eight patients received 50 micrograms/kg (1.8 X ED95). The ED25, ED50, ED75, and ED95 (estimated from linear regression plots of log dose vs probit of effect) were 11.5, 14.8, 19.0, and 27.3 micrograms/kg, respectively. Clinical duration (T25) was 27.8 +/- 10.3 (mean +/- SD) minutes at 1 X ED95 and 50.6 +/- 15.6 minutes at 1.8 X ED95. Time to recovery of the train-of-four ratio to 0.75 was 63.1 +/- 32.9 minutes at 1 X ED95 and 108.5 +/- 25.7 minutes at 1.8 X ED95. There were no significant changes in heart rate or mean arterial pressure after bolus administration of any dose of doxacurium.