Abstract: A total of 14 RCTs, with 4732 participants, were included in this review covering short-term (≤ 4 weeks; 6 studies), medium-term (> 4 weeks ≤ 6 months; 6 studies) and long-term treatment (> 6 months; 2 studies) with eszopiclone. Most RCTs included in the review included participants aged between 18 and 64 years, three RCTs only included elderly participants (64 to 85 years) and one RCT included participants with a broader age range (35 to 85 years). Seven studies considered primary insomnia; the remaining studies considered secondary insomnia comorbid with depression (2), generalised anxiety (1), back pain (1), Parkinson's disease (1), rheumatoid arthritis (1) and menopausal transition (1). Meta-analytic integrations of participant-reported data on sleep efficacy outcomes demonstrated better results for eszopiclone compared to placebo: a 12-minute decrease of sleep onset latency (mean difference (MD) -11.94 min, 95% confidence interval (CI) -16.03 to -7.86; 9 studies, 2890 participants, moderate quality evidence), a 17-minute decrease of wake time after sleep onset (MD -17.02 min, 95% CI -24.89 to -9.15; 8 studies, 2295 participants, moderate quality evidence) and a 28-minute increase of total sleep time (MD 27.70 min, 95% CI 20.30 to 35.09; 10 studies, 2965 participants, moderate quality evidence). There were no significant changes from baseline to the first three nights after drug discontinuation for sleep onset latency (MD 17.00 min, 95% CI -4.29 to 38.29; 1 study, 291 participants, low quality evidence) and wake time after sleep onset (MD -6.71 min, 95% CI -21.25 to 7.83; 1 study, 291 participants, low quality evidence). Adverse events during treatment that were documented more frequently under eszopiclone compared to placebo included unpleasant taste (risk difference (RD) 0.18, 95% CI 0.14 to 0.21; 9 studies, 3787 participants), dry mouth (RD 0.04, 95% CI 0.02 to 0.06; 6 studies, 2802 participants), somnolence (RD 0.04, 95% CI 0.02 to 0.06; 8 studies, 3532 participants) and dizziness (RD 0.03, 95% CI 0.01 to 0.05; 7 studies, 2933 participants). According to the GRADE criteria, evidence was rated as being of moderate quality for sleep efficacy outcomes and adverse events and of low quality for rebound effects and next-day functioning. Eszopiclone appears to be an efficient drug with moderate effects on sleep onset and maintenance. There was no or little evidence of harm if taken as recommended. However, as certain patient subgroups were underrepresented in RCTs included in the review, findings might not have displayed the entire spectrum of possible adverse events. Further, increased caution is required in elderly individuals with cognitive and motor impairments and individuals who are at increased risk of using eszopiclone in a non-recommended way.

Plain-language summary: On average, people taking eszopiclone fell asleep 12 minutes faster than those taking placebo, were 17 minutes less awake during the night and had, in total, about half an hour more sleep than people in the placebo group. As side effects, eszopiclone can cause unpleasant taste, dizziness, dry mouth, and tiredness during the day. Clinical studies did not find evidence that eszopiclone was causing serious harm or withdrawal symptoms or whether it was addictive if it was stopped and not taken after several weeks or months of treatment. Nevertheless, as clinical studies included in the review did not cover certain groups (e.g. elderly people with cognitive or motor problems or certain conditions of medication intake), it is important for patients to consult their doctor who knows their medical history and condition. Future research needs to compare eszopiclone with other sleep medications to help physicians and patients decide which of the available treatment options to prefer. In addition, sleep medications that are also well tolerated by elderly individuals and individuals with alcohol or drug problems need to be identified.