EVALUATION OF THE TIME COURSE OF ACTION OF MAINTENANCE DOSES OF ROCURONIUM (ORG-9426) UNDER HALOTHANE ANESTHESIA

The time course of action of rocuronium was compared using three different sizes of maintenance doses after at least three subsequent administrations of the same repeat dose in each patient under halothane anaesthesia. Following endotracheal intubation facilitated with 0.6 mg . kg-1 rocuronium (ORG 9426), muscle relaxation was maintained in three groups each consisting of ten patients, using increments of equal repeat doses of either 75 mug . kg-1, 150 mug . kg-1 or 225 mug . kg-1 equivalent to 1/4, 1/2 and 3/4 of the ED95 of this new compound, respectively. Maintenance doses were administered when the twitch height depression induced by the previous dose returned to 25% of its control value. The clinical duration of the intubating dose averaged 27 +/- 7.5 min (mean +/- s.d.). The time course of action of the various maintenance doses depended on their size, but not on the number of administrations. The durations of repeat doses averaged 8-9 min, 14-16 min and 19-23 min after the low, medium and high maintenance doses, respectively. No overt cumulative effects were observed.