Symptoms of insomnia -- difficulty falling or staying asleep -- are extremely common. A 2002 poll by the National Sleep Foundation found that 58 percent of adults experience them a few times each week and one-third have nightly symptoms. The problem is more common among frequent travelers, shift workers, women and the elderly. Another study found that about half of people with insomnia suffer from an underlying medical problem, such as depression, anxiety or chronic pain.
In about 15 percent of cases, sleep specialists say, chronic insomnia has no apparent underlying cause.
Gregg D. Jacobs, a sleep specialist at Beth Israel Deaconess Medical Center in Boston, said that long-term use of a sleeping pill is inappropriate for most patients because cognitive behavioral therapy works better than drugs in overcoming insomnia.
Sleeping pills, Jacobs said, are typically prescribed for brief periods. Some medicines used for sleep are habit-forming, such as a class of drugs known as benzodiazepines, which include Valium and Xanax. Doctors worry that long-term use of non-narcotic medications such as Lunesta can create psychological dependence that results when patients fear they can't fall asleep or stay asleep without them.
The other problem, said Jacobs, an assistant professor of psychiatry at Harvard Medical School, is that the long-term effects of Lunesta are unknown.
"Lunesta is like every drug approved by the FDA," said Jacobs. "We don't know what the long-term side effects are" or all the negative side effects seen during the clinical trials. "The message is: Buyer beware."
Sepracor's Southwell said that the drug, known generically as eszopiclone, is closely related to zopiclone, a sleep drug widely used in Europe and Canada for 20 years. Zopiclone, he said, has a good safety record. "If there were a safety defect, one would think they would have seen it by now," he said.
But Southwell acknowledged that oversight of prescription drugs varies from country to country in Western Europe. And some sleep specialists say that the potential market for Lunesta may be larger in the United States because of the aggressive marketing of drugs to consumers.
In the clinical trials of Lunesta, the most common side effects reported to the FDA were headache, an unpleasant taste and dizziness. When they first start taking the drug users are advised to "use extreme care when doing anything that requires complete alertness" such as driving, piloting an airplane or using heavy machinery.
Terri Bagley said she has been counting the days until Lunesta hit the market so she could call her doctor for a prescription.
Bagley, 43, who operates a housecleaning business in Pelham, N.C., said she has battled chronic insomnia for more than 20 years. She said it routinely takes her two hours to fall asleep at night, and she usually awakens four or five times each night, snagging a total of about four hours sleep and feeling perpetually exhausted during the day. None of the host of prescription or nonprescription drugs she tried made much difference, she said, and doctors ruled out underlying psychiatric or medical problems that might be causing her insomnia.
Then Bagley said, she enrolled in the clinical trial of Lunesta conducted at the Duke University Sleep Disorders Center. She said she is certain she got the drug rather than a placebo.
"I've never in my life slept that well or felt that good," Bagley said, adding that during the three months she took the drug she slept about seven hours per night with fewer and shorter awakenings.
Andrew D. Krystal, director of Duke's sleep center and one of the principal investigators of Lunesta, said that another advantage of the drug is that patients did not build up a tolerance to it. That is a common side effect of benzodiazepines, which typically require progressively larger doses to achieve the same effect.
Krystal, who has worked as a consultant for Sepracor, said while behavioral treatments are effective for some people, others have more intractable insomnia and need medication "which should be taken at the lowest possible dose for the shortest duration."
Whether Lunesta works better than its competitors remains to be seen. Chevy Chase sleep specialist Helene Emsellem said no large studies have compared Lunesta with other drugs.
"I think Lunesta clearly fills a needed niche in selected patients," said Emsellem, an associate clinical professor of neurology at George Washington University School of Medicine, who was involved in the clinical trials of the drug but said she has no other financial relationship with Sepracor. "But it's important for people to realize that insomnia is often a symptom and not a disease, and to sort out the problems."