Comparison of the effects of zolpidem and zopiclone on nocturnal sleep andsleep latency in the morning - A cross-over study in healthy young volunteers

Zolpidem (ZOL) and zopiclone (ZPC) are non-benzodiazepine hypnotics, with u nique effects on sleep architecture compared with conventional benzodiazepi nes. The two compounds have different profiles in action to two major subty pes of the GABA-A receptors, therefore different effects on sleep structure may be expected. In the present study, the effects of ZOL (10mg) and ZPC ( 7.5mg) were compared in nine healthy young male subjects during nine-night sessions, employing a crossover design. Time courses during the sessions we re significantly different between the compounds in the ratio (%) of S2 and S1. Compared to the baseline, an increase of S2 and a decrease of Si and S R were caused by ZPC, not by ZOL. SWS was increased by both ZPC and ZOL. Si gnificant changes by ZOL were found during the first 150-min, while changes by ZPC were mostly observed during the second 150-min. This might be relat ed to their half-lives. ZOL did not affect sleep latency in the morning, wh ile ZPC caused a significant decrease. Subjective sleepiness, however, was not increased in the ZPC or ZOL mornings. It was speculated that difference in the action to the GABA-A receptor subtypes might be related to the diff erences in the effects on the sleep architecture between the compounds. (C) 2000 Elsevier Science Inc. All rights reserved.