Lunesta, a popular prescription sleep aid, must change its label to warn users that they may still be too drowsy to drive safely and perform other activities after taking it, the Food and Drug Administration says.
The drug must also lower the recommended starting dose, the FDA said.
"To help ensure patient safety, health care professionals should prescribe, and patients should take, the lowest dose of a sleep medicine that effectively treats their insomnia," said Dr. Ellis Unger of the FDA's Center for Drug Evaluation and Research.
"Recently, data from clinical trials and other types of studies have become available, which allowed the FDA to better characterize the risk of next-morning impairment with sleep drugs."
A recent study showed that people who took 3 milligrams of Lunesta suffered severe impairment to coordination, driving skills and memory 7.5 hours after taking the drug, and the ill effects could last for as long as 11 hours.
Sometimes they did not feel drowsy, but they showed impairments.
FDA says the new recommended starting dose should be 1 milligram instead of 2 milligrams. “Using lower doses means less drug will remain in the body in the morning hours,” the FDA said in a statement.
Last year, the FDA required the makers of other sleep aids to lower their doses.
An estimated 8.6 million Americans take prescription sleeping pills including Lunesta, known generically as eszopiclone.
A federal study found that between 2005 and 2010, about 4 percent of U.S. adults had taken popular prescription drugs such as Lunesta and Ambien in the previous month.
“The FDA is continuing to evaluate the risk of impaired mental alertness with the entire class of sleep drugs, including over-the-counter drugs, and will update the public as new information becomes available,” the agency said.