U.S. federal health officials have warned that sleeping pills can cause "sleep-driving," a dangerous variation of sleepwalking, but Health Canada is still reviewing the products.

The Food and Drug Administration also warned the drugs can lead to other activities while patients are asleep, including eating and even having sex.

Sleep-driving made headlines last year when Rep. Patrick Kennedy smashed his car near the U.S. Capitol after taking Ambien, a popular insomnia drug.

He had also taken the anti-nausea drug Phenergan, which has a sedative effect.

Dr. Russel Katz, chief neurologist for the FDA, said the agency found more than a dozen reports of similar incidents connected to sleep drugs -- although millions take the medication, making the problem very rare.

"We really want people to know these things can occur, and these sleep behaviors can be perhaps to a large extent mitigated by behaviors the patients can control," he told The Associated Press.

He said that Ambien and any other insomnia drugs classified as "sedative-hypnotics" can potentially cause sleep-driving.

Katz advised patients to avoid taking the drugs with alcohol or other sedating drugs, and keep to the recommended dosage.

On Wednesday, the FDA said manufacturers of 13 sleep drugs will have to warn patients of two rare side effects:

  • "Complex sleep-related behaviours," including sleep-driving and less dangerous activities like making phone calls, eating food, or having sex -- all while still asleep.
  • Life-threatening allergic reactions and severe facial swelling.

But Health Canada experts are currently "reviewing the product monographs of sleep drugs marketed in Canada to determine if any revisions are needed," spokesperson Alastair Sinclair told CTV.ca in an e-mail.

He added that any such changes would be communicated to Canadians as soon as they become available.

Meanwhile, the FDA warned that some insomnia drugs could have a higher risk of sleep-driving than others, and asked manufacturers to conduct their own clinical trials.

Lisa Kennedy, a spokeswoman for Ambien manufacturer Sanofi-Aventis SA, said less than one out of 1,000 patients taking the drug reported sleep behaviours.

The insomnia drugs flagged by the FDA are:

  • Ambien
  • Butisol sodium
  • Carbrital
  • Dalmane
  • Doral
  • Halcion
  • Lunesta
  • Placidyl
  • Prosom
  • Restoril
  • Rozerem
  • Seconal
  • Sonata

With files from The Associated Press