Caverject is the first prescription drug approved for impotence.

It is self-injected into the penis shortly before sexual intercourse. The drug creates an erection by relaxing the smooth muscle tissue and dilating the major artery in the penis, which enhances the blood flow to the penis.

The drug's most common side effect is penile pain. Other side effects include bleeding at the injection site and an unhealthy, prolonged erection of four to six hours.

Chen, J, Godschalk, M, et al. The Lowest Effective Dose of Prostaglandin E1 as Treatment for Erectile Dysfunction. The Journal of Urology 1995; 153: 80-81. Chen, J, Godschalk, M, et al. Prostaglandin E1 as Treatment for Erectile Failure in Elderly Men, Journal of American Geriatrics Society 1994; 42:1263-1265.

For the estimated 10 to 20 million American men who suffer from impotence, Caverject provides an alternative to devices previously approved by FDA. A vacuum device involves placing a cylinder-like device and attached pump over the penis. By using the pump, blood is drawn into the penis, creating an erection. A constriction band is then placed at the base of the penis to maintain erection. A second treatment option, the penile implant, involves the surgical placement of cylinders in the penis and is available in a variety of designs.

FDA approved Caverject to treat impotence caused by neurological, vascular or psychological dysfunction. While psychological factors such as anxiety and depression can lead to sexual dysfunction, more than 85% of impotence cases have a physical cause, according to the Impotence Institute of America. A complete physical examination is important so that any underlying condition can be diagnosed and treated. Some common causes of impotence are diabetes, arteriosclerosis (hardening of the arteries), and high blood pressure. Also impotence has reportedly been caused by 16 of the 200 most commonly prescribed drugs, including drugs for high blood pressure, heart disease, and depression.