The FDA has announced it will require makers of certain sleeping pills to warn consumers about serious side effects including allergic reactions and sleep-driving. Somnambulism (sleep-walking) incidents involving complex tasks like driving, preparing and eating food, and having sex while asleep, with no memory of the tasks when awakened, have made the news in recent years. Now the FDA wants consumers and doctors to have direct warnings on labels and in brochures.

The Z-drugs are a class of drugs called pyrazolopyrimidines, the best-known being zolpidem (Ambien), eszopiclone (Lunesta, Imovane), and zalepron (Sonata). Considered better than addictive depressant drugs like Valium, they’ve become popular. But Z-drugs, in particular Ambien, have become notorious for bizarre and dangerous side effects like sleep-driving and sleep-eating.

Somnambulism does occur on its own, most commonly in childhood. There are centuries-old reports of sleep homicides and somnambulism is an established – if controversial – legal defence. Why Ambien in particular is linked to it, and why certain other drugs may or may not be, is unknown. Some sedating medications – including benzodiazepines – are actually used to treat somnambulism.

The FDA’s list of sedative-hypnotic drugs to carry the new warning include Seconal, a powerful barbituate rarely prescribed anymore, Halcion, an addictive benzodiazepine in use since the 1970s, Rozerem, a new drug that affects melatonin and is chemically dissimilar to all the other drugs on this list, and the Z-drugs. Somnambulism, especially sleep-driving, isn’t usually associated with the older drugs or Rozerem, and in a PubMed search I was only able to find one report of a similar event linked to zalepron. Barbiturates and benzodiazepines have well-documented serious risks of their own, of course, as do drugs that affect the hormone melatonin. (Search RxList to learn about each drug.)

It is curious, though, that the FDA has lumped this diverse group of medications together with the same blanket warning when they have different risks. Also, there are other medications commonly used as sleeping aids not listed (i.e. trazadone, olanzapine).

The FDA asked manufacturers to conduct more research. That seems quite understated.