March 28, 1998 FDA Approves Pill to Overcome Impotence
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." -------------- Read the Viagra package insert. View the actual FDA approval letter to Pfizer.(pdf) Pfizer press release announcing FDA approval. NIH Consensus Statement on Impotency Other impotency pills in development. -------------------- 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.) |
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Adapted from original story in New York Times (March 28, 1998) When a man is sexually stimulated, his brain sends signals to the nerves surrounding the penis. Those nerve cells release nitric oxide (NO), which in turn causes the penis to make another chemical, cyclic guanosine monophosphate (cGMP). cGMP is the key to having an erection. It widens blood vessels in the penis, and so blood gushes in, causing the penis to become rigid. As long as the man remains sexually stimulated, he continues to produce cGMP. But at the same time, he makes another chemical, phosphodiesterase Type 5 (PDE-5), which destroys cGMP. The result is an equilibrium: the production and degradation of cGMP are in balance, and the penis remains erect. When cGMP stops being produced, PDE-5 takes over, destroying the leftover chemical. The erection disapears. Viagra blocks PDE-5. If a man who is impotent takes the drug, it boosts the effects of cGMP in his penis by slowing its degradation. The result can be an erection in a man who would not normallly be able to have one. PDE-5 is not found in important quantities elsewhere in the body--the coronary arteries, for example. That is why Viagra did not alleviate angina. |
