A Polysomnographic Placebo-Controlled Evaluation of the Efficacy and Safety of Eszopiclone Relative to Placebo and Zolpidem in the Treatment of Primary Insomnia

Study Objectives: To evaluate the polysomnographic efficacy and the safety of a range of doses of eszopiclone relative to placebo in patients with primary insomnia. Zolpidem 10 mg was included as an active control. Methods: This multicenter, randomized, crossover study enrolled patients aged 21-64 years meeting the DSM-IV criteria for primary insomnia (n = 65). Patients received 2 nights treatment each with placebo, eszopiclone 1 mg, 2 mg, 2.5 mg, or 3 mg, and zolpidem 10 mg after randomization to one of 6 treatment sequences. Visits were separated by a 3-7 day washout. Objective efficacy was assessed by polysomnography (PSG). The primary endpoint was latency to persistent sleep (LPS); key secondary endpoints were sleep efficiency (SE) and wake time after sleep onset (WASO); other endpoints included wake time during sleep (WTDS) and number of awakenings (NAW), as well as patient-reported variables. Results: LPS and SE were significantly different than placebo for all active treatments (p < 0.05 for all). Significant differences from placebo were noted in the 3 objective sleep maintenance measures (WASO, WTDS, and NAW) for eszopiclone 3 mg (p < 0.05), which was not the case for zolpidem 10 mg or the other eszopiclone doses. The incidence of central nervous system adverse events was 23.4% for zolpidem 10 mg, 6.2% to 12.5% for the eszopiclone doses, and 7.9% for placebo. Conclusions: Relative to placebo, all active treatments were effective in reducing LPS and increasing SE. Eszopiclone 3 mg was significantly different from placebo on the 3 PSG measures of sleep maintenance (WASO, WTDS, and NAW). Significant differences between zolpidem 10 mg and eszopiclone (2 mg or 3 mg) were not observed for PSG-measured outcomes, although the study was not powered to detect differences between the active drug conditions.