FDA SANCTIONS VIAGRA, 1ST PILL FOR IMPOTENCE.

Byline: Gina Kolata The New York Times

Ending months of anticipation by patients, doctors and investors, the Food and Drug Administration on Friday approved the first pill for impotence.

The drug, sildenafil citrate, or Viagra, made by Pfizer Inc., is taken about an hour before intercourse and was found in studies to help 70 percent to 80 percent of impotent subjects. It acts on the normal physiological system in the penis and elicits an erection when a man is sexually stimulated; it has no effect if he is not.

Pfizer scientists, who discovered the erection-producing effect of the compound by accident six years ago, moved to develop the drug as soon as they realized what they had.

The company announced Friday that Viagra would be available by mid-April and would have a wholesale price of $7 a pill.

In anticipation of the FDA approval, and in expectation that resulting Viagra sales would quickly soar to several billion dollars a year, investors have pushed the price of Pfizer shares up 21 percent in the past two months.

Although discussion of impotence might evoke nervousness or jokes, urologists say it is no laughing matter. Pfizer said 30 million American men were afflicted, and a large study in Massachusetts has found that half of all men between the ages of 40 and 70 have problems getting or maintaining an erection.

``The prevalence is stunning,'' said Dr. Ridwan Shabsigh, a urologist who directs the New York Center of Human Sexuality at Columbia-Presbyterian Medical Center.

The other remarkable thing, said Shabsigh, whose entire practice is devoted to treating impotence, is that fewer than 10 percent of impotent men seek treatment.

Many, he said, deal with it like a secret shame, embarrassed to tell a doctor. Others assume the problem is an entrenched psychological one that would be difficult to resolve, or that it is a normal consequence of aging.

There were a number of impotence treatments before Viagra, but all carried one or more drawbacks that the drug will not have: a need for surgery, interruption of lovemaking, or pain.

In one available treatment, rigid prostheses are implanted in surgery, producing erections that are ``not very natural,'' said Dr. Harin Padma-Nathan, an impotence specialist in Los Angeles.

In another, the patient himself inserts suppositories into the end of the penis with a tiny plunger.

Then there are injections, like those tried by Michael Bierly, a 64-year-old Los Angeles lawyer, whose impotence began three years ago after surgery for prostate cancer.

``When you're diagnosed with this kind of disease, you're absolutely devastated,'' Bierly said. And so, although he knew that impotence might result from the cancer surgery, it was not a major concern at the time.

Later, when he discovered that he could no longer have intercourse, he felt desolate and frightened. But he kept his suffering to himself. ``It wasn't a problem that guys discussed,'' he said.

Eventually Bierly tried injections of chemicals that can force a flaccid penis to become erect.

``It simply didn't work,'' he said. ``It was cumbersome and painful. I was clumsy - you have to mix things up, and that took me 10 or 15 minutes. By the time I get done, she's asleep.''

One time, his erection lasted five hours despite intercourse during the interim. ``I would have gone to the emergency room,'' he said, ``but I didn't know what I would tell them.''

Bierly participated in Pfizer's clinical tests of Viagra, and the drug worked for him.

``It is the most natural thing in the world,'' he said.

Viagra was initially conceived as a drug to alleviate angina, the chest pains caused by the blocking of blood vessels that lead to the heart, said Dr. Ian Osterloh, who directed development of the drug for Pfizer. That effort proved disappointing: the company began small pilot studies in 1991, and by the end of 1992 was ready to abandon the drug.

There was, however, one unusual finding: some men, asked to report side effects, said they were having erections.

``At the time, it was more a curiosity than anything else,'' Osterloh said, since the researchers had no idea whether the men reporting the erections had previously been impotent. ``They were not very forthcoming,'' Osterloh said.

But soon afterward Pfizer researchers noticed a scientific paper that said nitric oxide, a short-lived chemical that is released from nerve endings in the penis, was important in creating erections. Knowing how Viagra worked, ``we began putting two and two together,'' Osterloh said, and the Pfizer scientists soon suspected that there was a reason the men were reporting erections: Viagra just might alleviate impotence.