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Hot Topic: Suvorexant - A Novel Drug for Insomnia Approved

Darrell Hulisz, Associate Professor, CWRU, School

January 2, 2015

Suvorexant (Belsomra®) is an orexin receptor antagonist and the first approved medication in its class. It was approved by the FDA in September 2014 as a C-IV drug for insomnia characterized by difficulties with sleep onset and/or sleep maintenance. Suvorexant is expected to be available in early 2015. Orexin is a neuropeptide that acts on the central nervous system receptors to promote arousal. Suvorexant is a highly selective antagonist for orexin receptors. Neuropeptides orexin A and B promote wakefulness by actin on orexin receptors OX1R and OX2R. Suvorexant works by blocking the OX1R and OX2R receptors.

Suvorexant is extensively metabolism in the liver. The major pathway is through CYP3A4 and the minor pathway is CYP2C19. Sixty-six percent of the medication is excreted unchanged in the feces and 23% through the urine. Suvorexant's half-life is 12 hours. Food will delay the absorption of Suvorexant delaying the Tmax by an hour and a half. The starting dose of Suvorexant is 10mg po once nightly. It should be taken within thirty minutes of bedtime. Patients should devote at least seven hours for sleep prior to taking the medication. Suvorexant may be increased to a maximum of 20mg nightly. The lowest effective dose should always be utilized. Suvorexant will be available in 5, 10, 15 & 20mg tablets. The lack of rebound insomnia or drug dependence potential might make Suvorexant a good choice for pharmacotherapy for patients with insomnia.

No renal dosing adjustments are required with Suvorexant. The medication should not be used in patients with severe hepatic impairment. Dose adjustments may be needed if Suvorexant is administered with other central nervous system depressants. If Suvorexant is concomitantly used with moderate CYP3A4 inhibiters, the recommended dose of Suvorexant is 5mg nightly & should not exceed 10mg. The use of Suvorexant is not recommended with strong CYP3A4 inhibitors.

Suvorexant is contraindicated in narcolepsy. Patients taking Suvorexant should be monitored for improvement in signs and symptoms of insomnia. This is indicative of efficacy. Insomnia should be re-evaluated if symptoms persist after seven to ten days of treatment. Patients should also be monitored for somnolence or central nervous system depressant effects. Worsening of depression, suicidality, or changes in behavior should also be watched.

Neurologic side effects of Suvorexant include sleep paralysis, somnolence, headache, and dizziness. Patients may also experience abnormal dreams and could potentially be at risk for suicide. The most common gastrointestinal adverse reactions include diarrhea and dry mouth. Cough and upper respiratory tract infections are also possible.

1. Herring WJ, Snyder E, Budd K, et al. Orexin receptor antagonism for treatment of insomnia: a randomized clinical trial of suvorexant. Neurology. 2012;79(23):2265-74.

2. BELSOMRA® (suvorexant) CIV Product Information. http://www.belsomra.com

3. FDA News Release. FDA approves new type of sleep drug, Belsomra. Aug 13, 2014. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm409950.htm

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