One complication or side effect of any medication for erectile dysfunction is something known as priapism, or a prolonged and painful penile erection lasting for more than four hours. This can be thought of as the body's inability to reverse an erection back to the flaccid or soft state.
Usually, under normal physiological conditions, when a man has an orgasm or there is lack of sexual stimulation, the body reverses the erection by constricting or "closing" the major blood vessels that allow blood to flow into the penis. With less blood going in, there is less "air" filling the balloon, and the balloon (the penis) deflates. The penis will then get softer because there is more blood leaving the penis than entering. With priapism, however, there is not enough blood leaving the penis, and an erection persists.
The problem and damage develops when there is no fresh blood getting into the penis and the cells of the corporeal bodies (the bodies responsible for erection) get less oxygen. Blood carries red blood cells to the body's tissues. The red blood cells carry oxygen. Oxygen is the food for the cells in the body. There must be a continuous supply of oxygen or the tissues become distressed and the cells can even die.
When an erection lasts for more than four hours, the cells of the penis get less oxygen (which is the food for their survival) because the blood is old and stagnant. The man will then experience pain because of this. As these cells die or scar, the penis will lose its ability to have a normal erection. The tissues of the penis must be healthy, relaxed and "stretchy" in order to allow the new blood to come in and allow a normal erection. After the four-hour time period, the penis cells will become less pliable. This makes normal future erections more difficult.
This condition can be caused by other medications or medical conditions as well. Patients with sickle cell disease are prone to this problem. The cells in sickle patients are abnormally shaped and can cause sludging that impedes normal oxygen delivery and red blood cell transport. Drugs, such as cocaine, and some psychiatric drugs, such as trazodone, can cause priapism as well.
Treatment for priapism depends on cause. If a patient has a known history of sickle cell disease, treatment can be directed to the restoration of normal cells and oxygen to the tissues. This is done first by giving the patient oxygen and intravenous fluids and pain control. In some cases, this is adequate for successful treatment, and the erection resolves. Some patients require further intervention.
The goals of treatment are to restore the flow of "new blood" in to the penis. This is first accomplished by draining the old blood out of the penis, usually with needles. Numbing medicine, such as lidocaine, is injected first to make the procedures more comfortable. Once the old blood is drained, saline is injected to clean out the old cells and restore normal blood flow.
If simple bedside maneuvers fail, the patient may require an operation to relieve the erection.