Researchers report that news in the journal Sleep -- and their findings now appear on Ambien CR's label.
Duke University's Andrew Krystal, MD, and colleagues studied 1,025 adults whose insomnia had lasted for at least three months. The patients had chronic primary insomnia, meaning their insomnia wasn't due to another condition.
About two-thirds of the patients got Ambien CR. The remaining patients got placebo pills. The patients didn't know whether they were taking Ambien CR or the placebo. All of the patients also got tips for better sleep.
Krystal's team told the patients to take their assigned pills as needed -- but at least three times per week and only one pill per night -- for six months.
Every morning, the patients reported whether they had taken their pill the previous night, how well they had slept, and whether they had any morning sleepiness or difficulty concentrating.
Patients taking Ambien CR slept better, concentrated better in the morning, and were less sleepy in the morning than those taking the placebo. Patients taking Ambien CR didn't take more pills as the study progressed, suggesting that their need for the pills didn't increase.
During the study's last week, the patients didn't take Ambien CR or the placebo. There was no sign of "rebound insomnia" -- worse insomnia than before drug treatment -- during that week.
Ambien CR's prescribing information now states that the drug has been shown to be effective for up to 24 weeks. The FDA approved that information on Dec. 20, 2007.
The study was funded by the drug company Sanofi Aventis, which makes Ambien CR.