RELATIVE POTENCY OF VECURONIUM IN MALE AND FEMALE-PATIENTS IN BRITAINAND AUSTRALIA

We compared the potency of vecuronium when given to similar patients i n Brisbane, Australia, and Cardiff, United Kingdom. Forty patients in each centre were anaesthetized using the same technique with propofol, fentanyl, nitrous oxide and vecuronium either 20 or 30 mu g kg(-1) by random allocation. Neuromuscular block was measured with similar Date x Relaxographs. There was no significant difference in potency between British and Australian patients. The ED,, and ED, for a British male of average weight were 29.5 mu g kg(-1) (95% confidence limits 27.3-32 .3 mu g kg(-1) and 51.3 mu g kg(-1) (44.3-63.9 mu g kg(-1)), respectiv ely. ED,, and ED,, for Australians were 5.5% greater, with confidence limits from 4% less to 17% greater. Females were significantly more se nsitive to vecuronium than males, requiring 22% less drug to achieve t he same degree of neuromuscular block (confidence limits 12-32%). The results are consistent with the ED(50) being independent of body weigh t when the dose is expressed as mu g kg(-2/3), but not as mu g or mu g kg(-1).