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 pa tients anesthetized with N2O-O-2-fentanyl-thiopene. Methods Sixty patients, ASA grade I,aged 18-50 years, scheduled for electiv e plastic surgery were studied. All patients were randomly divided into eit her the atracurium or rocuronium group. General anesthesia was maintained w ith 60% nitrous oxide and 40% oxygen, thiopentone, and fentanyl. Neuromuscu lar function was assessed using an accelograph with train-of-four (TOF) sti mulation at the wrist every 12 seconds. The percentage depression of the fi rst twitch (T-1) was used as the study parameter. The dose-response relatio nship of atracurium and rocuronium was determined by the cumulative dose-re sponse technique. Results According to the dose-response curves established by a least square s linear regression, the potency ratio of atracurium to rocuronium was 1:1. 2. There were significant differences in the ED50, ED90, and ED95 between t he two drugs. After the intravenous administration of equipotent doses of b oth drugs (1.5 x ED95), the duration of peak effect, clinical duration, and total duration were significantly different between the two drugs, but the ir recovery indexes were similar. Conclusions Atracurium and rocuronium are low-potency nondepolarizing relax ants with intermediate duration. As compared to atracurium, the neuromuscul ar blocking effect of rocuronium was about 20% less potent and its duration of action was shorter.