The “little blue pill” given to treat impotence might also help people overcome jet lag faster, a new study in rodents suggests.

Hamsters that received small doses of sildenafil, sold under the name Viagra, adjusted more quickly to laboratory simulations of a six-hour time-zone change than animals in the control group.

The researchers found that a single dose of sildenafil helped the animals adapt up to 50% faster than usual. They believe that because a one-off dose had this large an effect in hamsters, the drug might offer a simple way to combat jet lag in people.

Diego Golombek, at Quilmes National University in Buenos Aires, Argentina, and his colleagues conducted their experiments on hamsters accustomed to a regular cycle of 14 hours of light, followed by 10 hours of dark. Because hamsters are nocturnal animals, they use the running wheels inside their cages during the dark periods.


Prematurely turned on

Some of the animals were injected with about 70 micrograms of Viagra. Then, a few hours later, the cage lights were switched on prematurely, to simulate a 6-hour time zone shift – equivalent to flying from New York to Paris. The early switching on of the lights continued for the next few weeks.

The abrupt shift left many of the rodents disoriented and “jet-lagged”. Their body clocks failed to immediately adjust, so that even when the lights went out, they steered clear of their running wheels.

It took 12 days for the hamsters that did not receive Viagra to become accustomed to the shifted schedule, at which point they showed normal running activity soon after the lights went out. The hamsters that did receive Viagra, however, needed only about eight days on average to adjust to the schedule shift.

For humans, a general rule of thumb is that each hour in time difference between the origin and destination of a flight causes an extra day of jet lag. For example, a person flying from New York to Paris typically needs six days to fully adjust to the six-hour difference in time zones.

Golombek believes that Viagra helps protect against jet lag because the drug raises levels of a small molecule called cyclic guanosine monophosphate (cGMP) in the body. He explains that a spike in cGMP levels temporarily “speeds up” the internal body clock in the brain.

Changes in cGMP levels do not slow down the body clock, which helps explain why the drug does not seem to help hamsters cope with time shifts that simulate westbound flights. In other words, Viagra offers no jet lag protection for hamsters when their period of light exposure is adjusted to begin after the normal time.

Patricia Agostino, another team member, notes that people find it harder to adapt to eastbound travel: “Your body adapts better when you travel west.” A rodent study in 2006 found that severe time advances hastened death much more than time delays. Why that is the case is uncertain, but she speculates that “there are probably different molecular pathways that account for time advances and delays”.

No ‘side effects’

Sufficiently large doses of Viagra can produce a massive surge in cyclic GMP, causing blood vessels to widen, including those in the penis that enable erection. But in the jet lag experiment, the tiny doses given to the hamsters were too small to trigger erection.

A comparable dose for humans to the 70 micrograms of sildenafil given to the hamsters would be a small fraction of that found in the average Viagra pill, suggesting people might be able to take the drug to prevent eastbound jet lag without any effect on sexual desire.

“It’s true that some people will be worried about the – let’s call them side effects,” Golombek says. “But if we eliminate the erectile effects [by using low doses], I don’t see why people wouldn’t consider taking it.”

He adds that current treatments for jet lag involve taking multiple doses of the hormone melatonin over the span of several days, and this treatment does not work for all travellers. Taking a Viagra-like medication would be much simpler, according to Golombek, because it would probably involve only a single pill.

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0703388104)