Suvorexant: scientifically interesting, utility uncertain.

Objective: Suvorexant, a new hypnotic, is indicated for the treatment of insomnia characterized by difficulties with sleep onset and/or sleep maintenance, and is used long-term. This paper will briefly review suvorexant. Result(s): Orexin is a hypothalamic peptide which promotes wakefulness. By blocking orexin receptors, suvorexant induces sleep. Peaking 2 h after ingestion, it has a half-life of 12 h and is hepatically metabolized mainly by CYP3A. Kinetics are not affected by age but concentrations are higher in females and obese patients. There may be interactions with benzodiazepines, antidepressants and antipsychotics. Suvorexant is available in 15 mg and 20 mg doses at which benefits are moderate: after three months' treatment users fell asleep 6 min faster and slept 16 min longer than those on placebo. Studies with 40 mg showed greater benefits but more side effects: next day somnolence, fatigue, xerostomia and peripheral oedema. Hallucinations, sleep paralysis and somnambulism occur rarely. Tolerance, withdrawal and rebound do not generally occur at recommended doses. Conclusion(s): Suvorexant has not been trialled against other hypnotics, is expensive and its utility for insomnia in patients with psychiatric disorders is unknown. Currently, use of suvorexant could be considered where more established treatments are inappropriate.Copyright © 2017, © The Royal Australian and New Zealand College of Psychiatrists 2017.