Hypnotic action of melatonin during daytime administration and its comparison with triazolam

The present study was conducted to assess hypnotic action, effects on rectal temperature and dose dependency by daytime administration of exogenous melatonin (MLT) at 1 mg, 3 mg or 6 mg to subjects consisting of seven healthy juvenile adults. As a result, exogenous MLT significantly increased total sleep time and sleep efficiency, and MLT 6 mg was observed to demonstrate hypnotic effects that were nearly equal to those of triazolam at 0.125 mg. Rectal temperature was significantly decreased at MLT 1mg and 3 mg, there were no significant differences observed in the hypothermic effects at MLT 6 mg. These results indicate that exogenous MLT had dose-dependent hypnotic action on daytime sleep, and it is possible to consider that this hypnotic action was based on a direct-acting mechanism.