WASHINGTON (AP) -- 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.

"It's another option" for people with the main form of insomnia, difficulty in falling asleep, Meyer said. "By working through a different pathway, it's entirely possible that this might work for some people in ways that the other drugs do not."

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

The main warning: Rozerem is metabolized by the liver, so people with liver problems shouldn't take it, Meyer said

Manufacturer Takeda Pharmaceuticals said Rozerem will be available in late September but would not reveal a price.

Almost a third of adults have trouble sleeping, and about 10 percent have symptoms of daytime impairment that signal true insomnia. Rozerem joins a list of newer prescription sleep pills that work without many of the side-effect concerns of older agents.

Takeda Pharmaceuticals, based in Lincolnshire, Ill., is a wholly owned subsidiary of Takeda Pharmaceutical Co. Ltd., Japan's largest pharmaceutical company.

Copyright 2005 The Associated Press. All rights reserved.