Impotence occurs from interruption of the physical events that lead to an erection: 1) nerve impulses in the brain, spinal column, and penis, and 2) the response to those impulses by the muscles, fibrous tissues, veins, and arteries affecting the penis. A number of diseases, including diabetes and heart disease, can interrupt this process, and so can some medicines, injuries, and surgical procedures — for example, prostate surgery that damages nerves and blood vessels in or near the penis.
As you probably know, Viagra is a pill that is taken around an hour before expected sexual intercourse to improve penis blood flow — the basis of an erection. Other therapies include psychotherapy; devices that create a vacuum around the penis, causing an inner surge of blood that leads to erection; drugs the man injects into his penis or inserts into the urethra at the tip; and — if these therapies prove inadequate — surgery to implant a device to aid erection or to improve blood flow in the penis. As always, your doctor is your best source for specific information about your treatment needs.