MILWAUKEE – The drug that revolutionized sex soon may be perking up weary travelers and late-shift workers.

A study published last week found that Viagra helped hamsters recover from simulated jet lag, leading the researchers to conclude that it could benefit frequent fliers and people who rotate onto late-night work shifts.

“Taking into account that jet lag, as well as other circadian disorders, is increasingly common and has a profound effect on the quality of life, I believe this research … opens a completely original way of dealing with this kind of disarrangement,” said senior author Diego Golombek, a researcher with the National University of Quilmes in Buenos Aires, Argentina.

The drug might also be of benefit to people who periodically change their working hours, Golombek said.

“You could consider shift work as an extreme case of chronic jet lag where you would be “flying’ a few time zones every week,” he said.

Researchers said clinical trials still must be done to show that the drug works in humans, but given that Viagra and similar drugs already are being used safely by millions of men and, experimentally, women, many people may be tempted to try it for jet lag or to counter the negative effects of working a late shift.

Viagra, also known as sildenafil, is used to treat erectile dysfunction in men.

Although the drug works by increasing blood flow to the penis, it also seems to have an effect in the brain, where it can enhance circadian rhythm responses to light activation.

Essentially, it appears to allow a small region in the brain where the body’s master clock resides to more quickly reset itself in response to bright light.

Researchers not associated with the study said it presented an intriguing, first-ever finding, but they cautioned against using Viagra or similar drugs for purposes other than the approved use.

“It certainly has potential,” said Joseph Besharse, professor and chairman of cell biology, neurobiology and anatomy at the Medical College of Wisconsin. “It has the advantage of already being a prescribed drug.”

Viagra and some other erectile dysfunction drugs work by blocking levels of an enzyme produced in cells.

Besharse said that in a small region of the brain known as the suprachiasmatic nuclei, where the body’s internal master clock resides, the enzyme was blocked by administering Viagra. That, in turn, boosted levels of another brain substance that appears to play a role in allowing the master clock to reset itself.

Besharse, who was not a part of the study but who does research on the circadian rhythm system, said the physiology likely is similar in hamsters and humans.

For the study, the hamsters were injected with Viagra before an abrupt, six-hour advance in their light-dark cycle. The researchers then watched to see when the hamsters resumed a normal daily activity, running on an exercise wheel.

Compared with hamsters given saline, the ones treated with Viagra started running again 25 percent to 50 percent quicker, depending on the dose of the drug.

Just like in humans, the drug also had an erectile effect in the hamsters but only when it was given at a high dose.

Curiously, the benefit to adjusting the circadian rhythm cycle only was seen in a jet lag simulation of an eastbound flight. Researchers think that may be due to the fact that Viagra only affects the enzymes and brain chemicals that allow the body’s master clock to adjust to an advance in light/dark cycle rather than what would be encountered on a westbound flight across various time zones.

Still, Besharse, from the Medical College of Wisconsin, said what the researchers accomplished was no small feat.

Eastbound travel, such as taking a flight from the Midwest to France, really can throw a person off, he said.

“You feel lousy for a couple of days,” he said. “If you can limit that to one day, it would be helpful.”

Besharse said while there’s a good chance Viagra might help people adjust to eastbound jet lag, he’s not going to try it.

“I just try to eat and sleep with the locals,” he said. “I try to get on their schedule right away.”

While the study, which was published last week in the Proceedings of the National Academy of Sciences, suggests that Viagra might be beneficial in treating jet lag in people, caution is needed, said Mary Harrington, a professor of psychology at Smith College.

“This is the first study to report this effect and the study was conducted in hamsters,” said Harrington, who was not involved in the study. “This is not the time to encourage people to begin experimenting on themselves.”

She said she expected clinical trials on people would be done quickly.

The big question is, would Viagra or some of the other erectile dysfunction drugs help women recover from jet lag or working a night shift?

“If it were to work in humans then I would see no obvious reason for a sex difference,” said Joseph Beavo, a professor of pharmacology at the University of Washington.

Beavo, who was not a part of the study, said he would not recommend that a man or woman take a drug for a condition for which it has not been tested.

“Having said that, I would suppose that thousands of men have taken (an erectile dysfunction drug), particularly the long-acting Cialis, just before, during or after a plane trip across time zones.”