Antagonism of diazepam by aminophylline in healthy volunteers

Six healthy volunteers participated in a randomized, double-blind cross-over study of the effects of intravenous aminophylline on diazepam-induced sedation. Each subject participated in two phases and in each phase received either diazepam (15 mg intravenously) followed by placebo or diazepam followed by aminophylline (2 mg/kg intravenously). Critical flicker fusion times and reaction times were measured sequentially as indices of vigilance. Subjects also assessed their own vigilance on a visual analogue scale. Aminophylline given after diazepam significantly improved vigilance as measured by the visual analogue scale from 60 to 150 min after administration of diazepam, while total reaction time was significantly improved at 90, 210, and 270 min. There was no significant correlation between theophylline plasma levels and its effects on vigilance.