Flumazenil reduces the duration of thiopentone but not of propofol anaesthesia in humans

The effect of flumazenil (F) on the duration of anaesthesia produced by a single dose of thiopentone (T) and propofol (P) was investigated in a placebo-controlled double-blind trial. Eighty-four patients anaesthetized with N₂O in O₂ and either thiopentone 7 mg · kg^-1 or propofol 3 mg · kg^-1 for minor gynaecological procedures were studied. Patients were randomly allocated to pretreatment with either 0.5 mg of flumazenil (F) or 5 ml of normal saline (NS) in one of the following groups: T/NS, T/F, P/NS, or P/F. Anaesthetic requirements were assessed by recording the time between the injection of anaesthetic and the first movement observed during the procedure. The time elapsed from the administration of thiopentone to the first movement was 6.5 ± 1.6 min for the T/NS group and 5.3 ± 2.4 min for the T/F group (P < 0.05). The first movement after propofol administration was observed at 7.0 ± 2.2 min in the P/NS group and at 7.1 ± 4.5 min in the P/F group (NS). These data suggest that pretreatment with 0.5 mg of flumazenil iv reduces the duration of thiopentone but not of propofol anaesthesia.