The US Food and Drug Administration has finally approved Merck & Co’s insomnia drug Belsomra.

Belsomra (suvorexant) is an orexin receptor antagonist, the first approved drug in that class which regulates the sleep-wake cycle by altering the action of orexin in the brain. However the FDA has only approved the treatment at lower doses than Merck had originally hoped for.

Belsomra has been approved in four different strengths - 5, 10, 15, and 20mg - and Ellis Unger, director of the Office of Drug Evaluation I in the FDA’s Center for Drug Evaluation and Research said that using the lowest effective dose can reduce the risk of side effects, such as next-morning drowsiness. Furthermore, tests ordered by the FDA showed impaired driving performance in both male and female participants when the 20mg strength was taken and patients using the latter.

Last summer, the agency rejected Merck’s bid to also get approval for the 30mg and 40mg doses, citing safety concerns. Also the FDA has recommended that Belsomra be categorised as a controlled substance (schedule IV) because it can be abused or lead to dependence.

It will be dispensed with an FDA-approved medication guide once a final decision on scheduling is made by the US Drug Enforcement Administration. Merck noted that Belsomra should be available by late 2014 or early 2015, noting that the recommended dose is 10mg, taken no more than once per night and within 30 minutes of going to bed, with at least seven hours remaining before the planned time of awakening.

David Michelson, head of neurosciences at Merck Research Laboratories, noted that Belsomra is the result of more than a decade of study “and provides tangible evidence of our long-standing commitment to innovation”. He added that the approval “allows for the introduction of a new treatment option for patients suffering from insomnia”.

How great the take-up of this new option will be is debatable given the well-established competition facing Belsomra, notably low-dose generic Ambien (zolpidem) and controlled-release versions of the latter.