Merck & Co., the second-largest US drugmaker, has won approval to sell its treatment for insomnia that is viewed as a drug with fewer side effects than older pills such as Ambien.

The Food and Drug Administration cleared the sleeping pill called Belsomra in lower doses than Whitehouse Station, New Jersey-based Merck originally sought to market, according to a statement Wednesday from the agency. The drug may generate $305 million in sales in 2017, according to the average of six analysts' estimates compiled by Bloomberg, down from $516 million forecast before the FDA rejected the highest doses of the pill last year as possibly unsafe.

Suvorexant, the chemical name for Belsomra, is designed to turn off wakefulness while commonly used sleeping pills such as Sanofi's Ambien and Sumitomo Dainippon Pharma Co.'s Lunesta calm the brain. The Drug Enforcement Administration treats sleeping pills like sedatives that have a low potential for abuse yet still require some prescribing restrictions, such as how often the medicines can be refilled.

"To assist health care professionals and patients in finding the best dose to treat each individual patient's sleeplessness, the FDA has approved Belsomra in four different strengths - 5, 10, 15, and 20 milligrams," Ellis Unger, director of the Office of Drug Evaluation I in the FDA's Center for Drug Evaluation and Research, said in the statement. "Using the lowest effective dose can reduce the risk of side effects, such as next-morning drowsiness."


About 60 million Americans a year have insomnia frequently or for extended periods of time, according to the National Institutes of Health. Sales of generic and brand-name sleep aids totaled $1.5 billion last year, according to IMS Health Holdings Inc., a Danbury, Connecticut-based data analysis firm. The bulk of prescriptions, 41 million of 56 million, were written for generic versions of Ambien and Ambien CR.

FDA staff expressed concern when first considering the drug in May 2013 that patients who took higher doses of suvorexant experienced a greater risk of next-day drowsiness. The agency determined safety data didn't support sales of the 30 milligram and 40 milligram doses and directed Merck to start patients at doses lower than 15 milligrams.

Merck gained 1.4 per cent to $57.85 at the close in New York. The company's shares have increased 19 per cent in the past 12 months.

Before approving the drug, the FDA asked Merck to conduct a study on Belsomra's effect on driving the day after taking the drug. The study showed impaired driving in those who used the 20-mg dose, spurring the agency to say patients getting that dose should be cautioned against driving the day after.

Side effects of the drug include sleep-driving and other complex behaviors while not fully awake, such as preparing and eating food, making phone calls, or having sex, the FDA said.

Makers of sleep aids like Ambien that contain the active ingredient zolpidem were told by the FDA in January 2013 to lower by half the recommended doses for women. Zolpidem stays in women's bodies longer than had previously been known and can impair activities such as driving. In May, the agency also cut in half the recommended starting dose of Lunesta for men and women.

- Bloomberg