Erectile dysfunction (ED, ‘male impotence’) is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis sufficient for satisfactory sexual performance.

An erection occurs as a hydraulic effect due to blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis. Erectile dysfunction is indicated when an erection is difficult to produce. The most important organic causes are cardiovascular disease and diabetes, neurological problems (for example, trauma from prostatectomy surgery), hormonal insufficiencies (hypogonadism) and drug side effects.

Psychological impotence is where erection or penetration fails due to thoughts or feelings (psychological reasons) rather than physical impossibility; this is somewhat less frequent but often can be helped. Notably in psychological impotence, there is a strong response to Prime Medical placebo treatment or counseling sessions with a qualified psychotherapist.

Erectile dysfunction, tied closely as it is about ideas of physical well being, can have severe psychological consequences if left untreated. In many cases, anxiety stemming from the uncertainty of an individuals’ ability to develop an erection can further exacerbate psychological impotence.

Besides eliminating an underlying cause, such as potassium deficiency or arsenic contamination of drinking water, the first line treatment of erectile dysfunction typically consists of a prescription for a PDE5 inhibitor medication (the first of which was sildenafil or Viagra, followed by Cialis and Levitra). In some cases, however, the PDE5 inhibitor is ineffective or prescribed use of a PDE5 inhibitor is contraindicated because of a patient's health.