Dose-response curve and time-course of effect of vecuronium in male and female patients

To determine the differences between men and women in the dose-responsecurve and the time-course of effect of vecuronium, we studied 60 adultpatients (30 male and 30 female), ASA I, age 18-51 yr, undergoing electiveplastic surgery. Anaesthesia was maintained with nitrous oxide 60% inoxygen; thiopentone and incremental doses of fentanyl were given asrequired. Neuromuscular function was assessed mechanomyographically usingthe train-of-four (TOF) stimulation at the wrist every 12 s. The percentagedepression of T1 was used as the study variable. The dose- responserelationship of vecuronium was determined by a cumulative dose- responsetechnique. The dose-response curve in men was shifted in a parallel fashionto the right, indicating a decrease in the sensitivity tovecuronium-induced neuromuscular block, compared with women. The ED50, ED90and ED95 of vecuronium were 23.9 (4.7), 45.4 (11.2) and 55.7 (14.3)micrograms kg-1 in men and 18.4 (3.7), 33.5 (7.8) and 39.8 (9.6) microgramskg-1 in women respectively. There were statistically significantdifferences in these values between the two groups (P < 0.01 in eachinstance). After a total dose of vecuronium 80 micrograms kg-1,neuromuscular block was significantly longer in women than in men. Theduration of peak effect, clinical duration, and the total duration were18.7 (7.1), 26.6 (8.8) and 50.6 (16.0) min respectively in men and 26.0(7.2), 37.1 (11.2) and 65.9 (20.7) min in women. They differedsignificantly between men and women (P < 0.005 in each case).