Studies on the sleep-inducing effect of diphenhydramine hydrochloride

The present study was undertaken to clarify whether or not diphenhydramine is useful for sedative-hypnotic drug. EEG power spectra of delta band (0-4 Hz) at the frontal cortex in rats was used for an index of sleep. Diphenhydramine at doses of 2-20mg/kg, p.o. caused a dose-dependent shortening of sleep latency and prolongation of sleep duration. Significant effect was observed at a dose of 10mg/kg or more. These effects were almost the same as those of chlorpheniramine and less than those of brotizolam. The results clearly indicate that diphenhydramine is effective sedative-hypnotic drug for mild insomnia.