Medically reviewed by Lindsay Cook, PharmD Viagra (sildenafil) is an oral drug used to treat erectile dysfunction (ED) that ...

Viagra acts in response to sexual stimulation, enhancing the natural physiological process that leads to an erection, but it doesn't initiate it without arousal. How does Viagra work?

Most men and women know at least vaguely what Viagra does, but not everyone knows how it does it. So, what is Viagra, exactly, and how does it work ... staying hard after stimulation can sometimes ...