Viagara may help people with jetlag recover faster, say scientists who studied the impotence drug's effect on hamsters.

Rodents injected with small doses of sildenafil, marketed under the brand name Viagara, adapted faster to a simulated six-hour time zone change than did the hamsters which had not received the drug.

In a study published in Tuesday's Proceedings of the National Academy of Sciences, researchers at the Quilmes National University in Buenos Aires, Argentina recorded the daily time cycles of hamsters by monitoring their activity in an exercise wheel.

The Argentine scientists altered the light-dark cycle by switching on the lights six hours earlier than normal, simulating an eastward flight. The hamsters which had received an injection of sildenafil before the change in light-dark cycle, adapted to the new time cycle quicker than the hamsters which had not received the drug.

It took only eight days for the hamsters injected with Viagara to return to normal activity patterns, compared to 12 days for those who did not receive the drug.

The researchers believe that sildenafil blocks an enzyme which breaks down cyclic guanosine monophosphate (cGMP), a molecule known to have a role in setting the body-clock.