An experimental drug that mimics the effects of the hormone melatonin can reset the body’s circadian rhythms, bringing relief to jet-lagged travelers and night-shift workers, researchers reported Monday.

In a study of 450 people who were subjected to simulated jet lag in a sleep laboratory, a team from Brigham and Women’s Hospital in Boston found that the drug restored near normal sleep the first night it was used.

There were no aftereffects from the drug, minimal side effects, and people who took it performed normally the next day, said Dr. Elizabeth B. Klerman, one of the co-authors of the study published online in the journal Lancet.

And unlike conventional sleeping aids such as Ambien or Lunesta, she added, the new drug, called tasimelteon, has no potential for addiction or abuse.


The main limitations of the study were the relatively small size and the researchers’ inability to measure performance and mood after the drug was used, experts said.

The study was designed and funded by Vanda Pharmaceuticals Inc. of Rockville, Md., which developed tasimelteon, and all of the researchers reported receiving funds from Vanda or other pharmaceutical companies.

“This is a very promising first step,” said Dr. Jay Udani, who runs the integrative medicine program at Northridge Hospital Medical Center and who was not involved in the study. But the research “does not prove that it works for jet lag or shift workers,” he added. “That needs controlled studies in the field.”

The body’s sleep-wake cycle is controlled by melatonin, which is produced by the pineal gland in response to patterns of light and darkness. Higher concentrations of melatonin in the blood are associated with greater sleepiness.


Some research has shown that administering melatonin can adjust sleep cycles in travelers and workers, but the results have been mixed.

Because melatonin can’t be patented, drug companies have been interested in developing melatonin mimics, such as tasimelteon, which can be patented.

In the first part of the study, 39 patients’ normal sleep habits were monitored for three nights in the laboratory before they were sent to bed five hours early.

They were then given one of four different doses of tasimelteon or a placebo 30 minutes before bedtime.


Researchers monitored their sleep efficiency -- the percentage of time in bed they actually slept -- and the amount of time required for them to fall asleep.

Although all the subjects benefited from the drug, those receiving the highest dose had a sleep efficiency of 89% the first night, virtually the same as the 90% efficiency before the trail started. Those receiving a placebo had an efficiency of 71%.

Patients taking the highest doses slept for an average of about 428 minutes, compared with 430 minutes before the trial and 324 minutes for those taking a placebo. It took an average of seven minutes for them to go to sleep, compared with 11 minutes before the trial and 22 minutes for those receiving a placebo.

Blood analysis showed that the melatonin cycle of those receiving the drug was altered to match the new conditions.


“They would be expected to sleep better because their internal clock is on the right time,” Klerman said.

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thomas.maugh@latimes.com