[Influence of gender on the potency and course of action of rocuronium bromide]

The correlation between gender and the potency of certain neuromuscular blockers, including rocuronium, has been investigated. However, the methods used have been inconsistent. This study aimed to look further at the role of gender in order to arrive at definitive conclusions.

In a first and second phases of the study, rocuronium dose-response curves were constructed for patient groups as follows: 2 mixed-gender groups, 2 female groups, and 2 male groups. One group in each set received a single dose. In the other group the effect of the accumulated dose was measured after each of 3 fractions. The doses were transformed logarithmically. The effect was monitored by electromyography, and probit analysis was used to calculate the effective dose to induce 50%, 90% and 95% of the maximum effect (ED50, ED90 and ED95, respectively) in each patient. In the third phase, a bolus dose of 400 microg-Kg(-1) was administered to 3 additional groups. Onset time, maximum effect, speed of onset, duration of effect as the 10%-25% recovery index, and speed of recovery were recorded. In the fourth phase analysis was restricted to measurements during the period of onset.

No significant between-group differences in mean (SD) ED50, ED90, or ED95 values were observed after single doses (female group: 176 [68], 252 [97], and 285 [110] microg x Kg(-1), respectively; male group: 187 [69], 271 [100], and 307 [114] microg x Kg(-1); mixed group: 172 [73], 233 [98], and 258 [109] microg x Kg(-1)). Assessment of effect after cumulative fracional doses gave the following mean values for ED50, ED90, and ED95: 249 (63), 310 (79), and 334 (85) microg x Kg(-1) for the female group; 261 (60), 327 (75), and 354 (81) microg x Kg(-1) for the male group; and 242 (70), 305 (88), and 330 (95) microg x Kg(-1) for the mixed group. No significant differences in measures of effect were found after bolus administration in the third phase.

These results suggest that there is no significant effect of gender on potency or course of action of rocuronium bromide. Reports of such differences based on previous studies may be the result of problems in the methods applied.