After a clinical trial (for reduction of blood pressure) comparing what would later be known as Viagra with a placebo, a number of patients on the Viagra side went to their doctors and said "Er, well, er, could we possibly, er, keep taking this , er, drug?"
The researchers, after a few questions, found out why the patients wanted to continue taking it, and the rest is history.
Ask Bob Dole.
Wait, what?