How exactly does Viagra work?

Viagra works by causing the smooth muscles in your blood vessels to relax, increasing blood flow around and lowering the blood pressure. The active ingredient in Viagra, sildenafil, is also a PDE5 inhibitor; and it is this in particular that specifies an increase in blood flow to the penis. When a man is sexually stimulated his penile arteries go through a process to relax and enlarge. As they enlarge, the veins that remove blood from the penis are compressed thus restricting blood flow out of the penis, causing an erection. Although erectile dysfunction was originally thought to be purely psychological, the discovery of Viagra refuted this and it is now common fact that the nerves and blood vessels play a key role. If the nerves and blood vessels that facilitate the process of an erection do not work then erectile dysfunction occurs.