The little blue pill known for making time in the bed more enjoyable may also help weary jet travelers roll out of it in the morning.
New research shows Viagra may be the solution for travelers who suddenly find themselves needing to rise hours earlier as they cross time zones, at least if those travelers are hamsters.
A study at the Universidad Nacional de Quilmes in Buenos Aires showed that male hamsters who received an injection of sildenafil along with a 15-minute stimulation of light were able to adjust their internal clocks by six hours in roughly half the time that hamsters who did not receive the treatment took.
Sildenafil is the active ingredient in the erectile dysfunction drug Viagra.
Because humans and mammals have similar daily cycles, "there's no reason not to believe it should work in humans," said Diego Golombek, the lead investigator on the study.
At the same time, because the test was only done in animals, Golombek urged restraint for people thinking of trying it out.
"This is a study in laboratory animals, and clinical trials should be undertaken before deciding whether Viagra is a useful and safe treatment for those situations," he said.
Sildenafil works by sustaining a molecule that increases blood flow. Because that signaling molecule is sensitive to light, Golombek said, increasing its quantity makes the system more responsive to a change in patterns of light and dark.
At the same time, the researchers found that sildenafil was useful only for simulations of eastward travel. They found it ineffective when lengthening days to simulate travel westward.
While other treatments exist for jet lag, Golombek said that his research presents a novel approach to the problem -- using what is "generally a safe drug."
Viagra, he said, has been heavily studied for safety and effectiveness, so setting up a clinical trial "should be quite straightforward."
"It's a very good and interesting study," said Charmane Eastman, director of the biological rhythms lab at Rush University, who was not involved in the study.
While she sees follow-up studies coming with rats and mice, she believes human trials will be difficult to do properly.
But she agreed that the results would probably translate to humans.
"There's no reason to think that the basic mechanisms of resetting the [internal clock] would be different in humans compared to hamsters," she said. "The tricky part will be determining the optimal time for humans to take Viagra."
Extrapolating from the study, Eastman said humans would likely need to take Viagra six hours after their normal bedtime on the night before traveling eastward over six time zones.
"This could make for an interesting morning on the day of the flight!" she said.
Also, Eastman said, further research would probably be needed to find an optimal amount of Viagra to take, as the dosages for clock-adjustment in the study "could be embarrassing for the male traveler," and whether Viagra could work for female travelers too.
Eastman's own research uses the hormone melatonin, which plays a part in the natural sleep cycle in humans. She believes her method allows the body to reset its clock with fewer side effects than Viagra use.
She recommends beginning a regimen to shift the clock several days before traveling. While she has worked only with humans in lab situations, she said there is no reason to believe actual travel would be any different.
"We do have anecdotal evidence from people who have tried it," she said.
But while current sleep studies on time zone shifts have been simulated in labs, Golombek sees a need to test out these ideas in the real world.
"Jet lag trials might involve laboratory simulations, but we also need 'the real thing,' which means testing pharmacological treatments on long-haul air travel, which will certainly take some time," he said.