Double-blind, placebo-controlled study comparing effects of zopiclone and temazepam on cognitive functioning of insomniacs

The purpose of this study was to compare the cognitive effect of two medica tions frequently prescribed to patients suffering from insomnia. Using a do uble-blind design, we evaluated three parallel groups of 20 insomniac patie nts treated over a period of 3 weeks with zopiclone, temazepam and placebo, respectively. Our hypothesis was that the impact of zopiclone 7.5 mg/day o n cognitive functioning would be minimal 12 h after administration and that temazepam 30 mg/day would affect explicit memory, as is the case with othe r benzodiazepines. Patients were assessed at baseline following a 1-week, s ingle-blind placebo-intake period, and again at the end of each of the 3 we eks of the comparative phase. Then, in order to estimate the severity and d uration of potential rebound insomnia, patients were again assessed followi ng another 1-week, single-blind placebo-washout period at the end of the 3 weeks of treatment. The overall duration of the study for each patient was thus 5 weeks. The instruments of measure used were the Hamilton scale for a nxiety, daily self-rating questionnaire for assessment of sleep onset, dura tion and quality, and two large batteries of psychometric tests. The first of these batteries assessed memory and included span tests for short-term m emory, cued recall tasks for long-term explicit memory, and a word-completi on task for implicit memory; the second measured attention and concentratio n through the assessment of alertness, sustained attention and divided atte ntion. The sleep and anxiety results obtained confirm the findings of previ ous research. Zopiclone and temazepam possess a clinically significant hypn otic activity, with no rebound insomnia or anxiety, during the week of drug withdrawal. The results indicate that the two hypnotic drugs studied have little impact on cognitive functioning. We can therefore conclude that at t he doses administered over the 3 weeks, the two hypnotic drugs in question are relatively safe and efficacious in the treatment of insomnia and enable patients to enjoy a good quality of life. (C) 1999 John Wiley & Sons Ltd.