WASHINGTON – The government approved a new treatment for insomnia on Friday, the first prescription sleep aid not designated as a controlled substance.

Called Rozerem, the drug works differently from its competitors.

Rozerem is chemically related to the natural hormone melatonin, which helps regulate the body’s sleep-wake cycle, and is thought to work by stimulating melatonin receptors in the brain, explained Dr. Robert Meyer of the Food and Drug Administration.

Nor do studies show any sign that Rozerem, known chemically as ramelteon, causes dependence, the reason it was not designated as a controlled substance.