Ciramadol. The therapeutic dose range during balanced anesthesia.

In this study we attempted to determine whether ciramadol, a mixed opioid agonist-antagonist, would provide a satisfactory analgesic supplementation to an anesthetic technique for major surgery. Fourteen surgical patients received a balanced anesthesia technique with nitrous oxide, oxygen and muscle relaxants following thiopental induction. Incremental doses of ciramadol were administered as indicated by the somatic, hemodynamic or other sympathetic responses to anesthetic and surgical stimulations. The mean requirements of ciramadol during surgery were inferred from each patient's time-dose curve. The mean loading dose of ciramadol needed was 2.5 +/- 0.4 mg/kg and for maintenance of the analgesic effects, ciramadol had to be administered at a rate of 0.41 +/- 0.09 mg/kg.h. The important transformation rate (50.4%/h) was suggestive of an analgetic ceiling effect. Despite the very large amounts of ciramadol given, the hemodynamic responses to noxious stimuli were not fully suppressed with hypertensive episodes occurring during surgery. Recovery of spontaneous ventilation appeared promptly after completion of surgery and no evidence of respiratory depression was seen. Minute ventilation, respiratory rate and arterial PaCO2 remained within normal limits up to two hours after the end of anesthesia. No incidence of adverse psychotomimetic effects was observed.