How was Viagra discovered? 


This is actually a funny story. The research was not originally being done with impotence in mind. In 1985, researchers at Pfizer started looking for a class of chemicals with the potential for treating cardiovascular disease. They started out looking at hypertension, but that soon evolved into looking at angina, the syndrome that involves episodes of chest pain caused by poor blood flow to the heart muscle. In the discovery process, Pfizer made about 1,500 chemical compounds, and tested and screened them for over four years. In 1989, they found the chemical we now know as Viagra. Once Viagra had been identified and tested, researchers started clinical trials in the United Kingdom to treat angina, looking at safety and toleration of the drug. 

In about 1992, results from Phase II trials in angina patients showed Viagra to be less efficacious than had been hoped. But then something unexpected happened: Men refused to give their samples back, so the researchers suspected they were onto something. Indeed, demand for the drug was so high that some research subjects camped out on researchers' doorsteps, or even broke into labs, to get more Viagra. It turned out that - as a side effect - Viagra gave erections to men who had long been suffering from impotence. Of course, Pfizer did not miss the great business opportunity this presented, and went full-speed ahead with testing Viagra as an anti-impotence pill.

(from: http://www.american.edu/TED/viagra.htm)