Clinical and pharmacological actions of a bolus injection of suxamethonium: two phenomena of distinct duration.

Twenty-five healthy adult patients undergoing general anaesthesia for elective surgery were randomly allocated to five groups (n = 5) and their mechanical isometric adductor pollicis activity (twitch height (TH)), was monitored. The patients in groups I, II and III received suxamethonium 1 mg kg-1 followed by Org NC 45 40 micrograms kg-1 5 min (group I), 15 min (group II) or 30 min (group III) after complete recovery from muscle paralysis. The patients in groups IV and V received only Org NC 45 and 80 micrograms kg-1, respectively. Mean maximum TH depression (about 42% of initial value in group IV and 5% in group V) decreased to less than 4% in groups I, II and III regardless of the time interval between the injections of suxamethonium and Org NC 45. Mean duration to 90% recovery of Org NC 45-induced blockade was prolonged in patients in groups I, II and III when compared with the patients in group IV (28 min v. 12 min).