Lemborexant, sold under the brand name Dayvigo, is an orexin antagonist medication which is used in the treatment of insomnia. It is indicated specifically for the treatment of insomnia characterized by difficulties with sleep onset and/or maintenance in adults. The medication is taken by mouth. Side effects of lemborexant include somnolence, fatigue, headache, and abnormal dreams. The medication is a dual orexin receptor antagonist (DORA). It acts as a selective dual antagonist of the orexin receptors OX1 and OX2. Lemborexant has a long elimination half-life of 17 to 55 hours and a time to peak of about 1 to 3 hours. It is not a benzodiazepine or Z-drug and does not interact with GABA receptors, instead having a distinct mechanism of action. Lemborexant was approved for medical use in the United States in December 2019. It is a schedule IV controlled substance in the United States and may have a low potential for misuse. Besides lemborexant, other orexin receptor antagonists including suvorexant and daridorexant have also been introduced. Lemborexant is used in the treatment of insomnia in adults. A major systematic review and network meta-analysis of medications for the treatment of insomnia published in 2022 found that lemborexant had an effect size (standardized mean difference (SMD)) against placebo for treatment of insomnia at 4 weeks of 0.36 (95% () 0.08 to 0.63) and at 3 months of 0.41 (95% () 0.04 to 0.78). Lemborexant had similar effect sizes at 4 weeks as the other evaluated and marketed orexin receptor antagonists suvorexant (SMD 0.31, 95% CI 0.01 to 0.62) and daridorexant (SMD 0.23, 95% CI –0.01 to 0.48), whereas benzodiazepines and Z-drugs generally showed larger effect sizes (e.g., SMDs of 0.45 to 0.83) than lemborexant and the other orexin receptor antagonists. However, the review concluded that lemborexant and eszopiclone among all of the insomnia medications assessed had the best profiles overall in terms of efficacy, tolerability, and acceptability. Compared to benzodiazepines, there is a low risk of developing tolerance and dependence.