Ambien users sound alarm over sleepwalking risks.

Recent media reports have described bizarre episodes involving people who have taken Ambien--a popular prescription sleep aid--and awoken to find evidence that they ate a meal or took a drive around the neighborhood while slumbering. Some of these people have injured themselves in this somnambulant state. And they're starting to seek legal remedies.

"I know people who've taken Ambien and reported sleepwalking that they have no memory of," said Roman Silberfeld, a plaintiff attorney in Los Angeles who handles pharmaceutical litigation. "If the drug is capable of causing that sort of event, who's to say it isn't capable of causing others?"

In a class action filed this year in New York, responses to discovery and Freedom of Information Act (FOIA) requests are beginning to show that the number of affected users has been rising steadily in recent years, said attorney Susan Charna Lask, who represents the plaintiffs.

"I expect to uncover testing that is not adequate in relation to the use of the product," said Lask. "Meaning, they test a small sampling of people, but in reality there are millions who ultimately take the drug, and that number rises as they increase their marketing."

Ambien (zolpiden), which first hit the market in 1993, is manufactured and sold by the French company Sanofi-Synthelabo. Ambien is a sedative-hypnotic medication used to treat insomnia by calming the central nervous system. It is the most popular prescription sleep aid in the United States, where about 26.5 million prescriptions were filled in 2005.

Sanofi says the drug is "safe and effective" for insomnia when taken as directed--not while driving, not with alcohol, and only when the user will have at least eight hours to sleep. The complete package labeling cites side effects such as sleepwalking and hallucinations but says they are "rare," reported in fewer than 1 in 1,000 users.

In two widely reported incidents this year, Ambien users had combined the drug with other substances. Rep. Patrick Kennedy (D-R.I.) blamed a combination of Ambien and the antihistamine phenergan for his disoriented driving and crash near the Capitol, and a British passenger who took Ambien and drank two glasses of wine became agitated enough to divert a London flight to Boston. But many users have reported engaging in dangerous somnambulant activities after taking Ambien as directed.

States that do toxicology tests of impaired drivers ranked Ambien among the top 10 drugs found in their bloodstreams, according to the New York Times. In Wisconsin, for example, 187 drivers arrested between 1999 and 2004 tested positive for Ambien. In 2004, the FDA received 48 adverse-event reports involving Ambien without the use of other drugs, including three incidents of sleepwalking, six of hallucinations, and one traffic accident.

Jim Bartimus, a plaintiff attorney in Leawood, Kansas, considered a case where a woman taking Ambien walked at night and fell, bur "it would have been hard to prove" because she was also taking other medications, he said. "Juries are looking at personal responsibility harder than ever, so noncompliant use of the product, failure to follow directions--these are tough hurdles."

Bartimus still keeps an eye on the Ambien news. "If someone digs into this and finds that the manufacturer was aware of this to a much greater degree than we've been led to believe, then it could be like Vioxx, where people took it and were harmed because they didn't know what the manufacturer knew," he said.

Lask is prepared to dig. In March, she filed a class action with four plaintiffs injured after taking Ambien. The potential class would include those who have taken the drug since 2000 and were injured as a result of side effects of sleepwalking and sleep-eating. Lask estimates about 500 plaintiffs maybe involved. (Makinen v. Sanofi-Synthelabo, Inc., No. 06civ1762 (S.D.N.Y. filed Mar. 6, 2006).)

One of Lask's clients was sexually assaulted after opening the door to an attacker in her sleep; another drove while asleep and crashed her car. Another engaged in binge eating while sleeping, resulting in severe weight gain and an ulcer. The fourth was arrested for shoplifting and faces a dishonorable discharge from the military as a result.

Their lawsuit alleges that although scientific research links Ambien to sleepwalking behaviors, Sanofi failed to monitor and investigate reports of those effects and didn't test the product for them. The plaintiffs claim that Sanofi knew the risks but failed to warn class members, the public, government agencies, and the medical community, and it published false or misleading information about the drug's safety and potential adverse side effects.

The suit alleges negligence, strict liability, breach of implied warranty, fraud, unfair trade practices, and breach of express warranty. The plaintiffs seek compensatory and punitive damages.

The case is currently in discovery. Lask said she cannot say for sure that Sanofi hid facts in its pre- or post marketing testing, but her FOIA requests to the FDA have produced evidence of an increasing number of user complaints of walking, eating, and driving while asleep in recent years.

"If anything," she said, "I am satisfied that our filed complaint generated public awareness of a side effect that many people nationwide did not realize came from the Ambien they were taking. Now they are aware of something that neither Sanofi nor the FDA was going to make public because they considered it a small percentage [of the drug's users and] not worthy of comment."