Sleeping pills such as Ambien and Restoril may double someone's risk of a car crash — even after their effects should have worn off — and may raise the risk as much as having too much to drink, researchers reported Thursday.
A close look at medical and driving records showed that people who took any one of the three popular sleeping aids had anywhere between a 25 percent and three times higher risk of being involved in an accident while driving.
"We found that each of the medications independently was associated with an increased risk of motor vehicle crashes," Ryan Hansen of the University of Washington's school of pharmacy, who led the study, told NBC News.
The findings, published in the American Journal of Public Health, help justify U.S. Food and Drug Administration warnings about the pills.
In 2013, the FDA told makers to cut the recommended doses of sleeping pills because of research showing they can stay in the bloodstream at levels high enough to interfere with morning driving, which increases the risk of car accidents.
The FDA said doctors should aim to prescribe the lowest possible dose.
Hansen's team looked at the medical records and driving records of more than 400,000 people enrolled in a health plan in the state. They chose only adults who were also drivers.
Of them, just under 6 percent were written new prescriptions for sleeping aids between 2003 and 2008.
They collected data on the three pills: zolpidem, sold under the brand name Ambien; trazodone, sometimes sold under the brand name Oleptro; and temazepam, brand name Restoril. Each works through a different mechanism to help people sleep.
People who took Restoril had a 27 percent higher risk of being involved in a crash over the five years studied. People who took trazodone or Desyrel had nearly double the risk — 91 percent higher. Ambien users had the highest risk — they were more than twice as likely as non-users to have a car crash over the five years.
"These risk estimates are equivalent to blood alcohol concentration levels between 0.06 percent and 0.11 percent," Hansen's team wrote. The legal limit in all states for blood alcohol is 0.08 percent.
The effect wears off over time, the researchers found. It may be that people get used to the effects, or they may compensate for them.
"In our study we were just looking at new users of these medications," Hansen said. "We found that over time, the risk increased and it varied from medication to medication, but there was a cumulative effect that then waned after a period of time as well."
What's going on? It seems that people stay sleepy when they use sedatives, the researchers said.
These drugs stay in the blood for a long time, researchers know. "And so, they can have a variety of impacts on risk of crash, including people waking up in the middle of night without knowing it and driving, or waking up in the morning and driving to work and being slightly impaired by the medication still," Hansen said.
"These drugs can make you slow to react to complex situations in driving."
Mallinckrodt Pharmaceuticals, which makes Restoril, said it could not comment specifically on the study without further review.
"Mallinckrodt believes it's medications are safe and effective when used according to product labeling. We encourage patients and healthcare providers to discuss warnings and precautions that may be associated with any drug," the company said in a statement.
Sanofi, which makes Ambien, says virtually all prescriptions of the drug use a generic version now.
"It is important that patients only take zolpidem as directed by their physician. The FDA-approved label states do not take zolpidem unless you are able to stay in bed a full night (7-8 hours) before you must be active again," Sanofi said in a statement.
Ambien, especially, has been reported to cause strange side-effects in users, including sleep walking and taking part in other activities, including driving, with no memory of having done so afterwards.
"I hope that people who are taking these medications, who need to take these medications, will take a moment to talk to their doctor and pharmacist and really better understand the risks that are associated with this," Hansen said.
"It's not just a risk to them, if they're out there driving. It's also a risk to each and every one of us that's out on the road with people who are taking the medications."
At least 8.6 million Americans take prescription sleeping pills and between 50 million and 70 million Americans suffer from sleep disorders or sleep deprivation, according to the Institute of Medicine. Adults typically need between seven and nine hours of sleep a night, but more than a third of adults get less, according to the Centers for Disease Control and Prevention.