Viagra. Computer artwork of a Viagra pill joining male and female symbols. The image represents Viagra being beneficial to both men and women. Viagra (sildenafil citrate) unlike treatments that directly cause penile erections, affects the response to sexual stimulation. It enhances the smooth muscle relaxant effects of nitric oxide, which is released in response to sexual stimulation. Smooth muscle relaxation allows blood to enter the penis leading to an erection. There is evidence to suggest that Viagra's relaxation effects enhance women's sexual enjoyment also.