EFFECTS OF ZOPICLONE ON SLEEP ARCHITECTURE

The effects of hypnotic drugs on the structure of steep have been exte nsively studied by means of visual analysis of the EEG and, more recen tly, by the application of computer-assisted techniques. ideally a hyp notic drug should reduce the latency to sleep onset, enhance those asp ects of sleep which are related to recuperative processes (particularl y psychological recuperation), and leave unaffected other sleep functi ons which are already optimal even in insomniac patients. Zopiclone, a nonbenzodiazepine hypnotic drug, has been investigated in a range of studies aimed at delineating its effects on sleep architecture. In ter ms of the macrostructure of sleep, zopiclone appears to reduce the lat ency to sleep onset and to increase the overall duration of sleep, red ucing the frequency and duration of intra-sleep awakenings and thus en hancing sleep efficiency. The effects of zopiclone on the microstructu re of sleep, as revealed by analysis of EEG records, appear to be to r educe the latency to onset of stages 1 and 2, to reduce the duration o f stage 1 sleep whilst having a tendency to increase that of stage 2, to produce a slight increase in stages 3 and 4, and to have little or no effect upon REM sleep. It is concluded, on the basis of visual exam ination of sleep EEC records, that zopiclone is able to induce sleep w hilst having minimal impact upon steep architecture; such changes as a re produced are consistent with a beneficial effect upon sleep functio ns. These conclusions are supported by findings using computer-assiste d sleep analysis, which indicate that zopiclone increases spindle acti vity, which is related to increased sleep efficiency. Zopiclone shares many similarities with the benzodiazepines and barbiturates in its ef fects on sleep structure, but unlike many drugs in these other classes , it has the important advantage of leaving REM sleep unaffected and o f increasing, instead of decreasing, the recuperative sleep stages 3 a nd 4.