There are a variety of oral treatments for erectile dysfunction. One of them is Viagra, also known as Sildenafil. Erectile dysfunction by definition is the inability to have or maintain an erection. There are medical and psychological reasons for this. Most commonly it is a medical reason such as diabetes, neurological, circulatory or urological conditions. Viagra is one of the most common prescription treatments. It is also known as Revatio.

According to Medline Plus Drug Information (a service of the US National Library of Medicine and the National Institutes of Health) Sildenafil works to control the release of the enzyme phosphodiesterase. By controlling this enzyme the patient is able to have an erection when the penis is stroked during sexual intercourse. It will not cause an erection any other time.