Viagra for her might be on way

A drug that helps treat erectile dysfunction could also have an effect on a key artery in women, which could lead to an approach to help them, according to research at Medical College of Georgia.

The findings were presented this weekend at the annual meeting of the American Physiological Society, which is part of the larger Experimental Biology 2009 conference in New Orleans.

About 30 percent to 40 percent of U.S. women suffer from some form of sexual dysfunction, according to an article this month in Nature Reviews Urology . Yet compared with men, the problems in women are not easily addressed, said Kyan J. Allahdadi, a post-doctoral fellow in physiology at MCG and lead author of the study.

"There's a huge number of people that are not being treated basically," he said. The MCG team studied the theory that part of the problem in women might be inadequate blood flow. The MCG team looked at the internal pudendal artery in both male and female rats, which plays a key role in supplying blood to erectile tissue, Dr. Allahdadi said. Using sildenafil citrate, otherwise known as Viagra, and two other erectile dysfunction drugs, the researchers were able to get a response from both male and female arteries, he said.

However, the sildenafil got a response from the female arteries at a lower dose and the response seemed to oscillate back and forth from a relaxed to a contracted state, Dr. Allahdadi said.

"The type of response that we observed was drastically different" between males and females, Dr. Allahdadi said.

Sildenafil or Viagra works by inhibiting a specific enzyme called phosphodiesterase-5, which is known to be present in both male and female genital tissue; it is possible that another form of the enzyme in women could account for the different effect, said R. Clinton Webb, the chairman of the Department of Physiology at MCG and a co-author of the study. It could also explain why Viagra does not work in all men, Dr. Allahdadi said.

Sildenafil and other erectile drugs work by relaxing smooth muscle, which increases blood flow in the region, with the help of a chemical called nitric oxide. There are also nerves in the pelvic region that contain nitric oxide that could also be implicated in female sexual dysfunction and could also be affected by the drugs, Dr. Webb said.

"So I think that is why it is more complicated in erectile tissue compared to other blood vessels," he said.

Sexual dysfunction has a high correlation with heart disease (Viagra was originally developed to treat cardiovascular disease) and diabetes.

"Vascular dysfunction goes hand in hand with diabetes," Dr. Allahdadi said. "That's what we're looking at: Is there a breakdown in this normal vascular function, particularly this artery? That's where we're starting our investigation."

The next step might be to look at a disease model of diabetes in animals. But it also means looking at sexual dysfunction in a different way, Dr. Allahdadi said.

"A lot of people see treating sexual dysfunction as treating a lifestyle disorder," he said. "But if in fact we can appreciate it more as potentially an early marker for a cardiovascular event or a condition that may occur in your life, it puts more of a serious note to it."

Reach Tom Corwin at (706) 823-3213 or tom.corwin@augustachronicle.com.