A comparative study of the dose-response and time course of recovery of atracurium and rocuronium

Objective To compare the characteristics of the dose-response relationship and the time course of action between atracurium and rocuronium in adult patients anesthetized with N2O-O-2-fentanyl-thiopene. Methods Sixty patients, ASA grade I,aged 18-50 years, scheduled for elective plastic surgery were studied. All patients were randomly divided into either the atracurium or rocuronium group. General anesthesia was maintained with 60% nitrous oxide and 40% oxygen, thiopentone, and fentanyl. Neuromuscular function was assessed using an accelograph with train-of-four (TOF) stimulation at the wrist every 12 seconds. The percentage depression of the first twitch (T-1) was used as the study parameter. The dose-response relationship of atracurium and rocuronium was determined by the cumulative dose-response technique. Results According to the dose-response curves established by a least squares linear regression, the potency ratio of atracurium to rocuronium was 1:1.2. There were significant differences in the ED50, ED90, and ED95 between the two drugs. After the intravenous administration of equipotent doses of both drugs (1.5 x ED95), the duration of peak effect, clinical duration, and total duration were significantly different between the two drugs, but their recovery indexes were similar. Conclusions Atracurium and rocuronium are low-potency nondepolarizing relaxants with intermediate duration. As compared to atracurium, the neuromuscular blocking effect of rocuronium was about 20% less potent and its duration of action was shorter.