WASHINGTON (January 10, 2013)—The U.S. Food and Drug Administration is requiring makers of Ambien and similar sleeping pills to reduce the dosage of their drugs, based on studies suggesting patients face a higher risk of injury because of morning drowsiness.

The agency says new research shows that the widely used sleeping drugs remain in the blood at levels high enough to interfere with driving, which increases the risk of car accidents.

Regulators ordered drug manufacturers to cut the dose of the medications in half for women, who process the drug more slowly.

The FDA also recommends that manufacturers use the lower doses for men, though it will not be mandatory.

The new doses apply to all insomnia treatments containing the drug zolpidem, which is sold under the brands Ambien, Edluar and Zolpimist.