Dose-response relationship of rocuronium bromide during intravenous anaesthesia

The dose-response relationship and time course of neuromuscular block following bolus injections of rocuronium was determined in four groups of nine patients each under nitrous oxide-narcotic anaesthesia. Each patient received a total of 800 micrograms kg-1 rocuronium in two divided doses, i.e. 120 and 680, 200 and 600, 250 and 550, or 300 and 500 micrograms kg-1. The respective second dose was injected when, following the first dose, the evoked twitch tension had recovered to 95% of its control value. The mean ED50 and ED95 values, calculated from the first doses, were 103 and 271 micrograms kg-1, respectively. The DUR25 ranged between 11 +/- 4 (200 micrograms kg-1) to 14 +/- 3 min (300 micrograms kg-1) following the first and from 30 +/- 6 (500 micrograms kg-1) to 43 +/- 11 min (680 micrograms kg-1) following the second doses. The recovery index following the second doses varied between 14 +/- 5 (500 micrograms kg-1) and 24 +/- 20 min (600 micrograms kg-1), more than twice as long as following the first doses. We conclude that rocuronium is a muscle relaxant of low potency with an intermediate duration of action.