Suvorexant in the Treatment of Difficulty Falling and Staying Asleep (Insomnia).

Purpose of review: Insomnia affects more than 10% of the population and causes significant discomfort and disability. Suvorexant is an orexin receptor antagonist that specifically targets the wake-sleep cycle. This review summarizes recent and seminal evidence in the biological and physiological evidence of insomnia, the mechanism of action of suvorexant in treating insomnia, and clinical evidence regarding its use.

Recent findings: There is no single clear diagnosis for insomnia, and thus prevalence is not entirely clear, but it is estimated to affect 10%-30% of the adult population. Comorbidities include obesity, diabetes, and various psychiatric conditions, and insomnia likely has a contributing role in these conditions. Insomnia, by definition, impacts sleep quality and also wakefulness, including academic success and work efficiency. Insomnia is likely related to genetic susceptibility and a triggering event, leading to hyper-arousal states and functional brain disturbances. This leads to hyperactivity of the hypothalamic-pituitary-adrenal axis, over-secretion of corticotropin-releasing factor, and aberrancy in neurotransmitter release. Though several pharmacological options exist for the treatment of insomnia, there is equivocal data regarding their efficacy or limits to their use due to side effects and contraindications. Suvorexant is a novel dual orexin receptor antagonist, which is shown to improve sleep by reducing arousals. Unlike classical therapeutics, suvorexant does not alter the sleep profile; it prolongs the time spent in each sleep state. Though it may cause some somnolence, it is milder than reported with other drugs.

Summary: Multiple clinical studies support the use of suvorexant in insomnia. In primary insomnia, suvorexant is effective (over placebo), as measured by polysomnography and reported by patients, in both attaining and maintaining sleep. Similar, albeit to a smaller degree, results were found in secondary insomnia. Suvorexant carries two significant advantages over existing therapies; it has a much better safety profile in approved doses, and it preserves natural sleep architecture, thus promoting more restful sleep and recovery. Unfortunately, data exists mostly for suvorexant versus placebo, and head-to-head trials with common hypnotics are needed to assess the true efficacy of suvorexant over the alternatives. And while tolerance is less likely to develop, close monitoring of post-marketing data is required to evaluate for long term adverse events and efficacy.