Neuroendocrine, Autonomic, and Metabolic Responses to an Orexin Antagonist, Suvorexant, in Psychiatric Patients with Insomnia.

Aim: The aim of this study was to investigate the neuroendocrine, autonomic, and metabolic system responses to suvorexant in psychiatric subjects with insomnia. Design: This prospective study was conducted in Kusatsu Hospital in Hiroshima, Japan and included 40 psychiatric inpatients treated with suvorexant from December 2014 to April 2016. Methods: Questionnaire of Pittsburgh Sleep Quality Index (PSQI), Generalized Anxiety Disorder-7 (GAD-7), and Patient Health Questionnaire-9 (PHQ-9) scores were checked at baseline, Week 2, and Week 4, and fasting serum levels of prolactin, insulin, cortisol, noradrenaline, white blood cell count, and average pulse rate were measured at baseline and Week 4 and Week 8 after suvorexant initiation. Sequential change of the values were compared against baseline respectively. Results: Subjective sleep quality scores were significantly decreased at Weeks 2 and 4, and sleep duration, habitual sleep efficacy, and global scores were significantly decreased at Week 4 from baseline. Total scores on the Generalized Anxiety Disorder-7 and the Patient Health Questionnaire-9 significantly decreased at Week 4 from baseline. The levels of cortisol and white blood cell count were decreased, significantly at Week 8, and the levels of pulse rate were significantly decreased at Week 4 from baseline. The levels of noradrenaline decreased, although not significantly. The prolactin levels remained unchanged, and no trend was found in the insulin levels. Conclusion: Suvorexant treatment resulted in overall improvement in the quality of sleep and the severity of anxiety and depression. This dual orexin antagonist may be related to autonomic functions and neuroendocrine systems, especially in the hypothalamus-pituitary-adrenal axis in psychiatric subjects.