Belsomra (suvorexant) is now available at pharmacies in the United States for the treatment of insomnia in adults who have difficulty falling asleep and/or staying asleep, according to the drug’s manufacturer, Merck.

Belsomra is the only orexin receptor antagonist approved for the treatment of insomnia in the United States. Orexin is one of the many neurotransmitters in the brain involved in promoting wakefulness, and Belsomra selectively blocks orexin receptors.