Scientists at the pharmaceutical company Pfizer discovered the powers of Viagra (sildenafil citrate) by accident in the early Nineties during trials of a potential new angina drug named UK-92480.
Angina is a condition in which the vessels that supply the heart with blood constrict, triggering chest pain and breathlessness.
UK-92480 was found to do little to relieve pain, and Pfizer was on the verge of abandoning the drug when reports began to show a distinctive pattern; many male trial volunteers were experiencing an unusual side-effect . . . erections.