Ending months of anticipation by patients, doctors and investors, the Food and Drug Administration on Friday (March 27) 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 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.

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.

The most common side effect was headaches, afflicting 16 percent who took Viagra and 4 percent of those who took a placebo. Other side effects included flushing, indigestion, a stuffy nose and, for 3 percent of the Viagra patients, a mild bluish tinge imposed on their vision that lasted a few minutes to a few hours. The company reported that 2.5 percent of men taking Viagra dropped out of its studies; 2.3 percent of men taking placebos dropped out.

But doctors cautioned that Viagra is not a pill that will make normal men sexual virtuosos. There is no reason to believe it will revive flagging sex lives or allow men to partake in sexual endurance feats, they emphasized.

And insinuating that Viagra will become a recreational drug makes light of a serious medical problem that can wreak havoc with men's lives, medical experts said.

"This drug does not alter libido or desire," said Dr. Harin Padma-Nathan. "It does not create prolonged erections. And if you have normal erections, it will not make you feel more rigid."

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Viagra for Women?

How Viagra works.

Read the Viagra package insert.

View the actual FDA approval letter to Pfizer.(pdf)

Pfizer's official site for Viagra

NIH Consensus Statement on Impotency

Other impotency pills in development.

Abuse Potential

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USRF was an early participant in the U.S. Viagra clinical trials. (And we have continued to follow these men for more than two years.)