Info is great but how does it work?

Viagra, a prescription medication used to treat erectile dysfunction, works by blocking a chemical in the body that is normally responsible for reversing an erection. As a result, more of the chemicals responsible for the erection remain, so the muscles in the penis do not constrict. This allows blood to stay in the penis longer, which allows the man to maintain an erection. Because Viagra has no effect on the chemicals that cause an erection, it does not work without stimulation.