SAN ANTONIO -- More than 30 million men take drugs for erectile dysfunction, but the drugs marketed to treat male impotence are now being investigated for the treatment of more than a dozen diseases and health problems. Researchers say ED drugs like Viagra could turn out to be as versatile as aspirin.

Brian Kumnick is fighting throat cancer. He said he's been through months of radiation and surgery.

"Well, the radiation it's barbaric," Kumnick said. "It's really barbaric, and I've lost my taste buds, for example. I can't taste anything. Water tastes like acid going down."

He's part of a clinical trial to see if the ED drug Cialis can cure head and neck cancers.

"It'd be really nice to just take a pill that has a pleasant side effect," Kumnick said.

In preliminary studies, doctors at Johns Hopkins said Cialis energized patients' immune systems so their bodies could battle the cancer cells. Next they'll test to see if the drug also shrinks tumors.

Dr. Joseph Califano, a professor in the department of Otolaryngology at Johns Hopkins Hospital in Baltimore, MD, said, "When we looked at the blood of head and neck cancer patients, we could get their immune response to rev up to near normal levels, whereas they were suppressed maybe 75 percent, sometimes even 80 percent."

From fighting cancer, to helping hearts and lungs, doctors have found another use for Viagra.

Genevieve Cooper suffers from pulmonary hypertension -- lack of oxygen causes her to pass out.

"We just hear heart transplant, lung transplant," said Genevieve's mother, Sandra Hernandez. "It was devastating. She's my little girl."

Instead of a transplant, doctors prescribed Viagra in liquid form to open up her blood vessels.

Dr. James Swift, a pediatric intensive care physician at Sunrise Children's Hospital in Las Vegas, said, "Nitric oxide was developed for these types of issues in the lungs, and one of the byproducts was (that) this medication also can dilate blood vessels in other parts of the body and treat erectile dysfunction."

Califano said it's "very exciting to work with drugs that have already had safety data documented on them, because they can be very quickly moved into helping patients."