Suvorexant (Belsomra), a first-in-class orexin receptor antagonist drug, is now available on prescription in the United States for adults with insomnia.
Suvorexant, which is marketed by Merck, has been shown in clinical trials to help people with insomnia to fall asleep faster and to stay asleep throughout the night. It is thought to work by blocking the action of orexin, a neurotransmitter that promotes wakefulness.
The label recommends that the lowest effective dose of the drug be used and not to exceed 20mg per day; it is available as 5 mg, 10 mg, 15 mg and 20 mg strengths. It should be taken only once per night, within 30 minutes of going to bed, and with at least seven hours remaining before the planned time of waking.
In clinical trials, suvorexant was associated with side effects including daytime sleepiness, dizziness, weakness, confusion, feeling “drugged” or light-headed, and strange dreams. At the request of the US Food and Drug Administration, Merck studied next-day driving in people who had taken suvorexant and found that the 20-mg dose was associated with impaired driving performance.
Accordingly, people taking the 20-mg dose should be warned against next-day driving or activities requiring full mental alertness.
The label also notes that there is a risk of sleep-driving and other complex behaviours while not being fully awake, particularly if the person has consumed alcohol or other substances with central nervous system depressant effects. Suvorexant is contraindicated in patients with narcolepsy.
Suvorexant has been classified as a Schedule IV controlled substance, reflecting the potential for abuse or dependence.