Effectiveness of low-dose amitriptyline and mirtazapine in patients with insomnia disorder and sleep maintenance problems: a randomised, double-blind, placebo-controlled trial in general practice (DREAMING)

Background Low-dose amitriptyline and mirtazapine are widely prescribed off-label for insomnia disorder. However, evidence of their effectiveness from placebo-controlled studies is lacking. Aim To assess the effectiveness of low-dose mirtazapine and amitriptyline in patients with insomnia disorder. Design and setting Pragmatic, double-blind, randomised, placebo-controlled trial undertaken in general practices in the Amsterdam region, the Netherlands. Method Patients (aged 18–85 years) with insomnia disorder and sleep maintenance problems for whom non-pharmacological treatment was insufficient were randomised to mirtazapine (7.5–15 mg/day), amitriptyline (10–20 mg/day), or placebo for 16 weeks (optional double-dose regimen in week 2–14). Insomnia Severity Index (ISI) scores (range 0–28) were assessed at baseline and again at 6, 12, 20, and 52 weeks. The primary outcome was an ISI total score at 6 weeks that was clinically relevant and signified either ‘improvement’ (>7 points lower than baseline) or ‘recovery’ (total score ≤10 points). Results In total, 80 participants were included. At 6 weeks, in the intention-to-treat analyses, mirtazapine and amitriptyline each led to statistically significantly lower ISI scores when compared with placebo: mirtazapine mean difference = –6.0 points (95% confidence interval [CI] = –9.0 to –3.0), amitriptyline mean difference = –3.4 points (95% CI = –6.3 to –0.4). At 6 weeks mirtazapine resulted in statistically significantly higher improvement and recovery rates (52% and 56%, respectively) compared with placebo (both 14%), whereas amitriptyline (with rates of 40% and 36%, respectively) did not. From 12 weeks onwards no statistically significant differences in ISI scores were observed. Conclusion Compared with placebo, low-dose mirtazapine provided a statistically significant and clinically relevant reduction of insomnia severity at 6 weeks, but not at later time points. Low-dose amitriptyline resulted in a statistically significant reduction at 6 weeks, but this was not clinically relevant. The results do not support the prescription of low-dose amitriptyline and mirtazapine for several months in patients with insomnia disorder in general practice. Based on the results, GPs may consider prescribing off-label low-dose mirtazapine for a period of about 6 weeks in case non-pharmacological treatment is insufficient.