Taking Zolpidem at High Altitude May Be Unsafe

By Lorraine L. Janeczko 

NEW YORK—Climbers who take zolpidem at high altitude may put their performance and safety at risk, a new study from Europe suggests.

"Sleep is altered at high altitude leading many mountaineers to use hypnotics in order to improve sleep efficiency," the study authors pointed out in Sleep, online August 7. "While after a full night at altitude the short-acting hypnotic zolpidem does not appear to alter cognitive function, residual adverse effects should be considered following early waking-up as performed by mountaineers."

"This study reiterates the concept that there are no 'shortcuts' to sleep health and maximizing of performance," said Dr. Sara E. Benjamin, a neurologist specializing in sleep medicine and a clinical associate at the Johns Hopkins Center for Sleep in Columbia, Maryland.

"Zolpidem use will affect reaction time, cognitive performance and postural/balance tasks within the hours immediately after dosing," Dr. Benjamin, who was not involved in the study, told Reuters Health by email. She added, "Zolpidem is not designed to be used with restricted sleep hours followed by an immediate task."

Senior author Dr. Samuel Verges of Grenoble Alpes University in Grenoble, France, and colleagues conducted a randomized double-blind controlled cross-over study involving 22 healthy, physically active male and female adult volunteers who resided below 1,000 meters of altitude and were not acclimatized to high altitude.

The researchers evaluated the volunteers during two nights at sea level and two nights at 3,800 m, four hours after taking zolpidem (10 mg) or placebo at 10 PM.

The researchers did polygraphic recordings until they woke the volunteers up at 1:30 AM. Soon afterward, the participants completed questionnaires to evaluate sleep quality, sleepiness and acute mountain sickness symptoms; they performed two cognitive tasks (Simon task and duration-production task) at rest and during exercise. The researchers also evaluated their postural control.

Altitude exposure did not significantly affect mean reaction times, but it did significantly increase the Simon effect due to the reaction time being lengthened only in incongruent trials.

Zolpidem significantly increased mean reaction times at sea level and at altitude (+25.3 ms), but the drug had less effect during exercise.

Zolpidem also altered the center of pressure area (236 mm2 with zolpidem vs 119.6 mm2 with placebo; P<0.001). The drug did not affect the apnea-hypopnea index and the mean arterial oxygen saturation, but it improved sleep quality (P<0.001). Zolpidem also increased acute mountain sickness symptoms and sleepiness (P<0.05).

"The previous studies that cite a positive effect of zolpidem on performance in a high-altitude climbing environment were based on tasks performed with sufficient sleep, eight hours after use," Dr. Benjamin said. "If mountain climbers need to wake up at 1:30 AM to start climbing again, I would hope they go to sleep earlier than 10 PM the night before."

She noted that the small sample size and few female participants were limitations of the study.

"There are gender differences in the pharmacokinetics of zolpidem metabolism, and the recommended dosage is 5 mg for women, but all test subjects were given 10 mg," she explained. "I would expect the negative effects of the 10 mg drug to be stronger in women, but I do not think that the sample size of the study could power that type of interpretation."

"Another limitation was that I do not think the study subjects were as physically fit as the real climbers; they had no more than two endurance training sessions per week," she added.

Dr. Thomas Roth, director of Sleep Disorders and Research Center at Henry Ford Hospital in Detroit, told Reuters Health by email, "The results were not surprising, and the authors did not find any differences in the results between high altitude and sea level."

"This medication is safe and effective when used as directed by the FDA and the European Medicines Agency," advised Dr. Roth, who also was not involved in the study. "Take it when you have 7 to 8 hours of sleep left to go. Do not take a sleeping pill and get up in 5 hours. If you do, you will be impaired."

Dr. Verges did not respond to requests for comment.

The study did not have commercial funding. Dr. Roth said he "has consulted with almost all sleep medications, including Sanofi-Aventis, the manufacturer of the original zolpidem."

SOURCE: https://bit.ly/2PKqDIg

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