REGULATORY ROADBLOCK: The Food and Drug Administration says it won't approve high doses of Merck & Co.'s experimental insomnia drug, suvorexant, because of safety concerns. It could approve lower doses than Merck wanted, but new studies will be needed.
THE DRUG: Suvorexant would be first in a new class of sleep medicines that block chemical messengers in the brain that help keep people awake. But it can cause daytime drowsiness, trouble with driving and suicidal thinking, and it can interact with other drugs.
THE PATIENTS: About a third of adults have trouble sleeping. Many aren't happy with existing insomnia medicines.