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Hypnotic and hypothermic action of daytime-administered melatonin

Mishima K, Satoh K, Shimizu T, Hishikawa Y

Psychopharmacology, 1997

Abstract

Six healthy male volunteers (average age = 22.5 years) received orally melatonin (MLT; 3 mg or 9 mg) or placebo at 0930 hours in a randomized, single-blind, cross-over study. Both doses of exogenously administered melatonin (ex-MLT) induced transient, significant suppression of core body temperature (BT) compared to the placebo condition. There was no significant difference in the degree of BT suppression among the two MLT conditions in spite of significantly higher levels of serum MLT with the close of 9 mg, suggesting that there may be a threshold level of ex-MLT inducing the hypothermic action. Daytime administered ex-MLT also induced a significant sleep-inducing effect only in the 9 mg condition, while 3 mg ex-MLT failed to produce statistical significance. These findings suggest that the sleep-inducing action of ex-MLT occurs only at relatively high doses, and this action is probably not due to its BT lowering action. The present study led us to assume that ex-MLT produce its therapeutic effect for circadian rhythm sleep disorders through induction of circadian phase-shifting preceded by an acute, transient hypothermic action rather than light entrainment after setting sleep time by induction of sleep propensity.

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Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design.

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