Potency and hourly maintenance requirement of combinations of mivacurium and pancuronium in adults.

PURPOSE To evaluate the dose-response and maintenance requirements of a combination of mivacurium and pancuronium (cMP) in clinical practice. METHODS In a randomised, open clinical study, 70 patients, 17-50 yr of age, were anaesthetised with propofol, alfentanil and nitrous oxide in oxygen. Thirty patients received mivacurium and 20 patients received pancuronium to establish dose-response curves for these agents. Hourly maintenance requirements of mivacurium and pancuronium to maintain 90-95% neuromuscular blockade (NMB) were determined. Thereafter, 20 additional patients received cMP in incremental doses to establish a cumulative dose-response curve for cMP followed by maintenance doses of cMP. NMB was recorded by adductor pollicis electromyography. RESULTS The ED95 values for mivacurium and pancuronium were 100 and 66 micrograms.kg-1, respectively; and for the cMP 2:1 (in mg:mg basis), 32 micrograms.kg-1 mivacurium together with 16 micrograms.kg-1 pancuronium. This cMP was 1.8 times more potent than one parent agent (P < 0.0001). When cMP 2:1 was used, 60% of normal maintenance requirement of pancuronium reduced the requirement of mivacurium by > 90%. If cMP 20:1 was used, then 20% of normal maintenance requirement of pancuronium reduced the requirement of mivacurium by > 70%. Neostigmine 35 micrograms.kg-1 given at T1 10% recovery following cMP reversed the NMB to a TOF ratio of 0.70 in 9.5 +/- 3.9 min. CONCLUSION These results reflect considerable synergism between mivacurium and pancuronium. The cMP is near intermediate-acting and the NMB is easily reversed with neostigmine. By using cMP, it may be possible to save some pharmacological costs during maintenance of anaesthesia.