COMPARATIVE CLINICAL-PHARMACOLOGY OF ROCURONIUM, CISATRACURIUM, AND THEIR COMBINATION

Background: The comparative clinical pharmacology of cisatracurium and rocuronium and their combinations has not been reported. In this stud y, the authors compared the relative potency and the clinical profile and characterized the interaction of both drugs. Methods: Two hundred twenty adults classified as American Society of Anesthesiologists phys ical status I and anesthetized with propofol-fentanyl-nitrous oxide we re studied. In part 1, the neuromuscular-blocking effects of cisatracu rium and rocuronium were assessed after administration of bolus doses of 20-50 mu g/kg and 100-300 mu g/kg, respectively. In part 2, we comp ared the time course of 1xED(50), 1, 1.5, and 2xED(95), doses of both drugs (where ED50 and ED95 are, respectively, the doses producing 50% and 95% depression of the first twitch height [T1]). In part 3, equief fective combinations of both drugs were studied to characterize their interaction. Results: The calculated ED50 values and, their 95% confid ence intervals were 111 (107-115) and 215 (207-226) mu g/kg for rocuro nium and cisatracurium, respectively. Compared with equipotent doses o f cisatracurium, rocuronium had a faster onset, and a faster spontaneo us T1 and train-of-four recovery times that were significant except at maximum recovery with the 2xED(95) dose. The interaction between rocu ronium and cisatracurium was synergistic, and the time profile of the combination group was different from that of the single-dose groups. C onclusions: Cisatracurium is four to five times more potent than rocur onium. Rocuronium had a faster onset of action, a shorter clinical dur ation, and a faster spontaneous recovery rate compared with equipotent doses of cisatracurium.