What alternatives are there to Viagra? For a more detailed explanation of this process see our Viagra information page. Viagra relaxes the muscle cells in the blood vessels supplying the penis, allowing an increased blood flow. What should I tell my healthcare provider before taking Viagra? Therefore this increased blood flow increases the chance of achieving an erection. Erections occur when blood flows into the penis. Research in support of the link between pornography and erectile dysfunction argues that porn can desensitize sexual response.