Erectile dysfunction, or impotence, can be a total inability to achieve erection, an inconsistent ability to do so, or a tendency to sustain only brief erections. These variations make defining impotence and estimating its incidence difficult. Estimates range from 15 million to 30 million, depending on the definition used.

In older men, impotence usually has a physical cause, such as disease, injury, or side effects of drugs. Any disorder that causes injury to the nerves or impairs blood flow in the penis has the potential to cause impotence. Incidence increases with age: About 5 percent of 40-year-old men and between 15 and 25 percent of 65-year-old men experience impotence. But it is not an inevitable part of aging. Generic Viagra

impotence is treatable at any age, and awareness of this fact has been growing. More men have been seeking help and returning to normal sexual activity because of improved, successful treatments for impotence. Urologists, who specialize in problems of the urinary tract, have traditionally treated impotence; however, urologists accounted for only 25 percent of Viagra mentions in 1999.

When a man is sexually aroused, the arteries in the penis relax and widen, allowing more blood to flow into the penis. As the arteries in the penis expand and harden, the veins that normally carry blood away from the penis become compressed, restricting the blood flow out of the penis. With more blood flowing in and less flowing out, the penis enlarges, resulting in an erection. Because Generic Viagra causes a physiological change it is able to treat most ED sufferers regardless of how long they have had difficulty achieving or maintaining an erection.