For those who have trouble sleeping, there may soon be new ways to summon the sandman.

Several pharmaceutical companies are working on new approaches to treat insomnia. The compounds are meant to work differently than current leading sleep aids such as Ambien and Lunesta, which, while generally safe, can have troubling side effects because they act on many areas of the brain. By contrast, many of the drugs being developed target particular systems responsible for sleep and wakefulness. The hope is that they will have fewer side effects and less potential for addiction and cognition problems the next day.

About 30% of American adults have insomnia symptoms each year, scientific studies estimate. Some 10% of the population has chronic insomnia, which is generally defined as having difficulty sleeping at least three times a week for a month or more. Chronic insomnia sufferers also feel tired, cranky or foggy-headed during the day.

Insomnia comes in various forms. Some people have a tough time falling asleep and others wake in the middle of the night and have trouble getting back to sleep. Some people rise for the day too early. Insomnia can increase the risk for other conditions, including heart disease, diabetes and depression.

Merck & Co. is investigating a compound that inhibits the action of orexin receptors, which in turn interferes with the activity of orexin, a chemical in the brain that produces alertness. The company hopes to file for Food and Drug Administration approval by next year. Last fall, Somaxon Pharamaceuticals Inc. launched Silenor, a drug that blocks histamine receptors, which are important in regulating wakefulness. Neurim Pharmaceuticals Ltd. is seeking FDA approval of Circadin, a prescription form of the sleep-promoting hormone melatonin. The drug, which delivers melatonin in a prolonged-release formulation, is already available in Europe, Asia and the Middle East. Other research efforts are targeting specific serotonin receptors, a move that could promote deeper stages of sleep. There is also growing interest in a form of cognitive behavioral therapy that treats insomnia.

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