Those sleeping pills you see advertised on TV and in magazines may sometimes have a bizarre side effect that could be dangerous: what experts are calling "sleep-driving."

The FDA has found that sleeping pills, including the market leaders Ambien and Lunesta, can cause the odd behavior, which is said to be like sleepwalking, but behind the wheel. In sleep-driving, people drive while not fully awake after using a sleeping pill, and have no memory of having done so. Similar but less hazardous behaviors noted include making phone calls or preparing and eating food--all while still asleep.

The FDA has ordered the makers of 13 sleeping products to include stronger label warnings about these rare but serious side effects.

Manufacturers have been told by the FDA to write letters to doctors to notify them of the new warnings. From now on, all prescription sleeping pills will come with "Medication Guide" brochures that spell out the risks in easy-to-understand language.

Although the FDA notes that reports of such incidents have been rare, it also suggested that they may be extensively under-reported.

The products mentioned are Ambien, Butisol sodium, Carbrital, Dalmane, Doral, Halcion, Lunesta, Placidyl, Prosom, Restoril, Rozerem, Seconal, and Sonata.

And here I thought that talking on cell phones while driving was dangerous. Now there may be people driving who are actually asleep!