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★Sleep medication linked to bizarre behaviour
12:44 06 February 2007
NewScientist.com news service
Roxanne Khamsi
New evidence has linked a commonly prescribed sleep medication with bizarre behaviours, including a case in which a woman painted her front door in her sleep.
UK and Australian health agencies have released information about 240 cases of odd occurrences, including sleepwalking, amnesia and hallucinations among people taking the drug zolpidem.
While doctors say that zolpidem can offer much-needed relief for people with sleep disorders, they caution that these newly reported cases should prompt a closer look at its possible side effects.
Zolpidem, sold under the brand names Ambien, Stilnoct and Stilnox, is widely prescribed to treat insomnia and other disorders such as sleep apnea. Various forms of the drug, made by French pharmaceutical giant Sanofi-Aventis, were prescribed 674,500 times in 2005 in the UK.
A newly published report from Australia's Federal Health Department describes 104 cases of hallucinations and 62 cases of amnesia experienced by people taking zolpidem since marketing of the drug began there in 2000. The health department report also mentioned 16 cases of strange sleepwalking by people taking the medication.
Midnight snack
In one of these sleepwalking cases a patient woke with a paintbrush in her hand after painting the front door to her house. Another case involved a woman who gained 23 kilograms over seven months while taking zolpidem. "It was only when she was discovered in front of an open refrigerator while asleep that the problem was resolved," according to the report.
The UK's Medicines and Healthcare products Regulatory Agency, meanwhile, has recorded 68 cases of adverse reactions to zolpidem from 2001 to 2005.
The newly reported cases in the UK and Australia add to a growing list of bizarre sleepwalking episodes linked to the drug in other countries, including reports of people sleep-driving while on the medication. In one case, a transatlantic flight had to be diverted after a passenger caused havoc after taking zolpidem.
Hypnotic effects
There is no biological pathway that has been proven to connect zolpidem with these behaviours. The drug is a benzodiazepine-like hypnotic that promotes deep sleep by interacting with brain receptors for a chemical called gamma-aminobutyric acid. While parts of the brain become less active during deep sleep, the body can still move, making sleepwalking a possibility.
The product information for prescribers advises that psychiatric adverse effects, including hallucinations, sleepwalking and nightmares, are more likely in the elderly, and treatment should be stopped if they occur.
Patient advocacy groups say they would like government health agencies and drug companies to take a closer look at the possible risks associated with sleep medicines. They stress that strange sleepwalking and sleep-driving behaviours can have risky consequences.
"When people do something in which they're not in full control it's always a danger," says Vera Sharav of the New York-based Alliance for Human Research Protection, a US network that advocates responsible and ethical medical research practices.
Tried and tested
"The more reports that come out about the potential side effects of the drug, the more research needs to be done to understand if these are real side effects," says sleep researcher Kenneth Wright at the University of Colorado in Boulder, US.
Millions of people have taken the drug without experiencing any strange side effects, points out Richard Millman at Brown Medical School, director of the Sleep Disorders Center of Lifespan Hospitals in Providence, Rhode Island, US. He says that unlike older types of sleep medications, zolpidem does not carry as great a risk of addiction.
And Wright notes that some of the reports of "sleep-driving" linked to zolpidem can be easily explained: some patients have wrongly taken the drug right before leaving work in hopes that the medicine will kick in by the time they reach home. Doctors stress that the medication should be taken just before going to bed.
The US Food & Drug Administration says it is continuing to "actively investigate" and collect information about cases linking zolpidem to unusual side effects.
The Ambien label currently lists strange behaviour as a "special concern" for people taking the drug. "It's a possible rare adverse event," says Sanofi-Aventis spokesperson Melissa Feltmann, adding that the strange sleepwalking behaviours "may not necessarily be caused by the drug" but instead result from an underlying disorder. She says that "the safety profile [of zolpidem] is well established". The drug received approval in the US in 1993. (721)
