Are women more sensitive to a pre-curarization dose of rocuronium than men?

There is increasing evidence that there are gender-related differences in the pharmacodynamics of neuromuscular blocking drugs. However, it is not known whether gender influences the pharmacodynamics of a pre-curarizing dose.

In the first part, we measured the neuromuscular blockade after administration of rocuronium 0.03 mg/kg (10% of ED(95)) after induction of anaesthesia in 20 patients (10 female and 10 male patients) by electromyography. In the second part, 40 female and 40 male patients were observed for signs and symptoms of muscle weakness 2.5 min after injection of rocuronium 0.03 mg/kg before loss of consciousness. Succinylcholine-associated post-operative myalgia (POM) was also assessed.

Median twitch heights were comparable between the two groups: 95.5 (range: 85-97; female) vs. 96.0 (range: 85-99; male), (NS). Train-of-four ratios were 97.5 (range: 64-100; female) vs. 99.0 (range: 52-100; male) (NS). Signs and symptoms of muscle weakness were observed in 64 (80%) patients, but there were no gender-related differences. The incidence and severity of POM did not differ significantly between the study groups.

Pre-curarization with rocuronium 0.03 mg/kg affected men and women equally. Nor was the incidence and the severity of muscle weakness affected by gender.