Hamsters on Viagra have less jet lag
Hamsters given Pfizer Inc.’s Viagra adapted more quickly to changes in their internal clocks, scientists said. Hamsters given sildenafil, the chemical name of the drug sold as Viagra, adapted more easily to altered patterns of light exposure to simulate changes caused by air travel across time zones. Long-haul travel desynchronizes the body’s alignment to the day-night cycle, leading to the disorientation of jet lag.
A person traveling east experiences difficulty falling asleep and awakening; a person traveling west falls asleep and awakes earlier, according to the Centers for Disease Control and Prevention in Bethesda, Maryland. Viagra helped the hamsters with eastward travel, said head researcher Diego A. Golombek, a scientist with the Laboratorio de Cronobiologica in Buenos Aires.
“Because Viagra is widely used, it’s something we can easily imagine being useful,” said Christopher Colwell, an associate professor of psychiatry at the David Geffen School of Medicine at the University of California Los Angeles. “This study is very cool — not a huge surprise, but a neat proof of principle.”
Most drugs that can be used to mimic circadian rhythms “you wouldn’t want to take yourself,” Colwell said, citing unwanted side-effects. He wasn’t involved in the study. “This could be applied to humans pretty easily.”
Hamster rhythms
Hamsters are the species of choice for studies of circadian rhythms, Golombek said. That’s because they have precise patterns, which are easily measured by watching when they run on their exercise wheels.
“As anyone who has a hamster as a pet will attest, they go to the wheel at the same time every night,” Golombek said. “They love wheels.”
The researchers synchronized the hamsters to a 24-hour day by simulating light-dark cycles. Once the hamsters adjusted to a cycle, they shifted the light-dark phases forward six hours. One group of hamsters was given saline; the other was given Viagra. The hamsters given Viagra got used to the change 4 days faster, on average, than their counterparts given a placebo. Viagra eased the transition that mimicked crossing the international dateline from west to east, known as phase advancing, and had no effect on a transition that mimicked westward travel.
“All animals, including humans, have a harder time with phase advancing,” said Colwell in a telephone interview today. “Humans are unique in our ability to screw up our timing system — you know, jet lag, shift work, staying up too late playing video games, or whatever.”
Viagra for angina
Viagra was initially developed for angina, which is chest pain that occurs when the heart muscle doesn’t get enough blood. The same chemical, marketed under the name Revatio, is used to treat pulmonary arterial hypertension. Another study recently showed that the drug may help in treating idiopathic pulmonary fibrosis.
Viagra keeps another chemical in the brain, called cyclic GMP, from decomposing. Because cyclic GMP is involved in adapting to light, the researchers hypothesized that increasing its levels would accelerate animals’ adaptation to a new schedule.
The researchers performed the study with several dosage levels of Viagra, Golombek said. Low doses elicited a circadian response and had no erectile effects; at higher doses, Viagra stimulated both the circadian rhythms and the hamsters’ penises. It’s difficult to compare hamster dosage with human dosage because hamsters have a faster metabolic rate, Golombek said.
“This research is particularly relevant since it opens a completely original way of dealing with” jet lag, Golombek said.
Though Viagra is typically prescribed to men, there is no reason to think that it wouldn’t be equally effective in women for jet lag, Colwell said.
“Every bit of our biology is influenced by our timing system,” Colwell said. “We have a clock inside us, and in order for us to work properly, it has to be synchronized with the environment.”
Human Trials Needed
The researchers said studies hadn’t been performed in humans and that clinical trials must be undertaken before Viagra is considered a safe and useful treatment for the condition.
“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,” Golombek said.
Pfizer, the world’s largest drugmaker, had no connection to the study.
“While this is an interesting area of research, Pfizer has not conducted any trials assessing Viagra use as a treatment for jet lag and has no plans to do so,” Pfizer spokesman Francisco Gebauer said in an e-mailed statement today. “Viagra is approved only for the treatment of erectile dysfunction.”
Viagra did $434 million in sales the first quarter of 2007, an 11 percent increase from the first quarter of 2006. It is the New York-based drugmaker’s fifth-largest product.
