The Food and Drug Administration has recommended that the bedtime dose of the insomnia drug zolpidem be lowered because there's new evidence that, after taking the current dose, the level of drug remaining in patients' blood the next morning can impair activities that require mental alertness, including driving.

The FDA has received adverse event reports of driving impairment and car accidents associated with zolpidem, but it wasn't until clinical data using driving simulation and laboratory studies were conducted that the agency understood the full extent of the problem.

Zolpidem is available as a generic and is also a component of Sanofi's (NASDAQ:SNY) Ambien and Ambien CR, Meda Pharmaceuticals' Edluar, and NovaDel Pharma's (NASDAQOTH: NVDL) Zolpimist. Intermezzo, developed by Purdue Pharma and Transcept Pharmaceuticals (NASDAQ:PRTK), also contains zolpidem, but it's already dosed at a lower level since it's used for middle-of-the-night insomnia.

The drug is eliminated slower in women than in men, so the FDA is requiring drugmakers to lower the recommended dose for women from 10 mg to 5 mg for immediate-release products and from 12.5 mg to 6.25 mg for extended-release products. The new labels will also note that doctors should consider prescribing the lower doses to men as well.