Injection therapy, which has been used since 1990, involves the self-injection of medication into the shaft of the penis. It produces good quality erections for about 70 to 80 percent of men who have ED. The medications used, including prostaglandin E1, papaverine, and phentolamine, all relax the smooth muscle of the penis, allowing blood to flow into the penis and to not escape.

Injection therapy requires a prescription. A urologist will determine the correct dose and teach you how to inject yourself. Although it sounds scary and painful, most men do not report much discomfort. A very fine needle (the same kind used to give allergy shots) is used, and it is put into an area with very few nerve endings. In some men, however, the medicine itself, not the shot, does cause a burning sensation.

The upside is that the shot produces a very good erection that will last from 30 to 60 minutes, or longer. The erection may last even after ejaculation, and sometimes until the medication wears off, which could be as long as two or three hours.

Injection therapy is less risky than surgery, and the erections look and feel more natural than those produced by a vacuum device, although some men say that the erection produced by injection is also unnatural. But there are downsides, too. First, the thought of putting a needle into the penis may be a turnoff to many men. And, like the vacuum device, injection therapy means interrupting sexual activity and disrupting spontaneity. More troubling downsides include a 7 to 10 percent chance of scarring of the elastic tissue, causing a deformity to the erect penis, and the risk of getting priapism, which is an erection that won't go down. Priapism is more of a risk early in treatment, when the urologist is trying to fine-tune the correct dosage. Any erection that lasts longer than three or four hours requires a trip to the doctor or emergency room to prevent permanent damage to the penis.

Finally, there is the issue of cost. The cost of injection therapy depends on the manufacturer and ranges in price from $10 for each injection to $80 for a three-month supply of injections. Not all insurance plans cover injection therapy.

Though they might not be the preferred option, surgical treatments might succeed where non-invasive treatments have failed. We will discuss these measures in the next section.