Does sex difference influence the neuromuscular blocking potencies of vecuronium?

One hundred and fifty patients of ASA class I-II undergoing elective surgery were given vecuronium 0.1 mg·kg-1 under fentanyl- (NLA), halothane, enflurane, isoflurane, or sevoflurane anesthesia, and the spontaneous recovery was monitored to study the sex differences as to onset time, duration [(T1, train of four (TOF)], and recovery index (T1, TOF). The onset time was significantly shorter in women than in men under isoflurane and sevoflurane anesthesia. No significant differences were seen between the sexes in terms of duration and recovery index of both T1 and TOF. We suggest that the results regarding onset time were due to the differences in distribution volume and extracellular fluid volume influenced by the proportions of lean body mass, fat tissue, and the occasional menstruation in women. It remains unclear, however, whether or not the effects of volatile gases to the sensitivity of receptors may contribute to the observed sex difference. Similar durations and recovery indexes in any anesthetic method indicate that the drug's rate of elimination is similar between the sexes. In conclusion, female patients favor the rapid onset of vecuronium when used under isoflurane or sevoflurane, but the recovery from the paralysis seems to be the same between the sexes regardless of the type of general anesthesia used.