AbstractThe acute hypnotic effects of hydroxyzine 25 mg and 50 mg nocte, were examined in six male and six female volunteers. Continuous electrophysiological measures (C‐EEG) were taken to assess both nocturnal sleep and sleep tendency the following day. Both doses produced significant reductions in sleep onset latency and decreases in waking during sleep; reciprocal increases in sleep duration were also seen. Female subjects demonstrated a greater hypnotic response, including a dose‐dependent decrease in sleep onset latency. Increases in sleep duration following both doses were significant for the female group alone. C‐EEG measures of increased drowsiness the following day failed to achieve significance; although the largest effects on daytime sleepiness, including dose‐dependent increases, were again seen with the female subject group and corresponded with subjective ratings. These results demonstrate the hypnotic efficacy of hydroxyzine whilst failing to detect significant C‐EEG hangover effects. However, variability in response to antihistamines, registered here as differences between the sexes, requires further cons