Erectile dysfunction (ED) is defined as persistent difficulty achieving and maintaining an erection sufficient to have sex. Erectile dysfunction (ED), also known as impotence, is a type of sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual activity. Erectile dysfunction can have psychological consequences as it can be tied to relationship difficulties and self-image. Its causes are usually medical but can also be psychological. Normal erectile function can be affected by problems with any of the following systems: blood flow, nerve supply or hormones. Organic causes are usually the result of an underlying medical condition affecting the blood vessels or nerves supplying the penis. Numerous prescription drugs, recreational drugs, alcohol, and smoking, can all cause ED. Treatment depends on the cause. Exercise, particularly aerobic exercise during midlife is effective for preventing ED; exercise as a treatment is under investigation.For tobacco smokers, cessation results in a significant improvement.Oral pharmacotherapy and vacuum erection devices are first-line treatments,followed by injections of drugs into the penis, and penile implants. The PDE5 inhibitors sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis) are prescription drugs which are taken orally. A cream combining alprostadil with the permeation enhancer DDAIP has been approved in Canada as a first line treatment for erectile dysfunction.Often, as a last resort if other treatments have failed, the most common procedure is prosthetic implants which involves the insertion of artificial rods into the penis.