BOSTON — Terri Bagley spent nearly two decades searching for a way to get a good night's sleep.

She toyed with keeping her bedroom pitch black and sniffing the soothing smell of lavender. But neither those tricks nor over-the-counter and prescription medications made much of a difference.

Bagley, a 44-year-old operator of a small cleaning service in Pelham, N.C., is typical of the millions of Americans believed to suffer from chronic insomnia who until recently had mostly short-term solutions available. She found help in a clinical trial for Lunesta, one of a new generation of prescription sleep medications, and continued taking the drug after it hit the market in April.

"If you're tired for 20 years, you don't realize how much better you can feel until you start getting a full night's sleep again," she said.

An emerging class of sleep aids is spurring an advertising effort that industry watchers say could rival the saturation campaign for erectile dysfunction drugs.

"I would expect this to become a very active category of drugs in consumer advertising," said Judy Franks of Starcom Worldwide, a Chicago-based ad-buying agency.

U.S. advertising for prescription and over-the-counter insomnia drugs was nearly $68 million last year, according to TNS Media Intelligence, a media research firm. But spending in the first four months of this year alone was $48.7 million; at that rate, it could top $146 million this year.

The total is still far less than the $382 million spent last year to advertise erectile dysfunction drugs. But advertising industry officials expect spots encouraging insomniacs to talk with their doctor will become more frequent in coming months as more sleep aids hit the market.

"When a new competitor comes into the marketplace, it usually heightens spending on the part of all the competitors, because they need to defend their positions in the marketplace," said Michael Guarini, managing director of Ogilvy Healthcare, which is based in New York.

Lunesta is so far the only prescription sleep aid approved by the Food and Drug Administration for long-term use, in contrast with more established short-term medications such as Ambien and Sonata. While most of the eight FDA-approved sleep aids tend to lose their effectiveness after a week or so of use, Lunesta has been shown in Sepracor-financed clinical studies to remain effective for up to six months.

Some of the emerging new insomnia medications are believed to enhance the action of so-called GABA receptors within the brain believed to promote sleep, while minimizing the side effects more common with older drugs.

The short-term indication labeling on older drugs put doctors "into a very difficult double-bind," said Dr. John Winkelman, medical director of the Sleep Health Center at Brigham and Women's Hospital in Boston. "Patients complaining of chronic nightly sleeplessness were being treated with medicines that were only for short-term use. Now that double-bind has been lifted."

At least two other medications could win U.S. regulatory approval later this year or early next year: Pfizer Inc. and San Diego-based Neurocrine Biosciences Inc. are teaming up to develop indiplon, a GABA-receptor drug that hasn't yet been given a brand name, and Japan-based Takeda Pharmaceuticals is developing Rozerem, a drug that interacts with the natural hormone melatonin.

Like the heavily marketed erectile dysfunction drugs, the new insomnia medications are aimed at people who have gone largely untreated and may be unaware of new treatment options.

An estimated 126 million adult Americans experience at least one insomnia symptom a few nights a week, according to the National Sleep Foundation, a group that receives some of its money from drug companies. Only about a third of sufferers are actually diagnosed with insomnia, and a small fraction of those are treated with prescription medication.

Drug makers are trying to overcome concerns about addiction that were related partly to older barbiturate sleep aids, as well as lingering drowsiness associated with over-the-counter antihistamines.

"A lot of doctors have been historically somewhat reticent to prescribe these drugs, so a patient-driven marketing approach makes sense," said analyst David Steinberg of Deutsche Bank North America.