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Impotence (Erectile dysfunction)

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of erectile dysfunction.

Injections or Topical Treatments

Penile injections have now largely been replaced by PDE5 inhibitors such as sildenafil. Nevertheless, injection therapies employ various drugs that have properties that help achieve erection, even in many men who do not succeed with PDE5 inhibitors. The standard drugs used in injections include:

• Alprostadil
• Phentolamine
• Papaverine

Although any or all of these drugs are very effective, injections or other invasive methods of administration are awkward and uncomfortable.

Treatments Using Alprostadil

Alprostadil is derived from a natural substance, prostaglandin E1, and acts by opening blood vessels. It is an effective treatment for some men. It can be administered by:

• Injection into the erectile tissue of the penis (Caverject, Edex)
• Device that administers the drug through the urethra (MUSE system)

Candidates. Regardless of how it is administered, alprostadil works in many men with a wide range of medical disorders related to erectile dysfunction, including the following:

• Diabetes
• Prostate cancer treatments (early use of alprostadil injections after prostate cancer treatment, particularly when followed by a PDE5 inhibitor, may be helpful)
• Men who take nitrates
• Injury

Alprostadil is not an appropriate choice for the following individuals:

• Men with severe circulatory or nerve damage
• Men with bleeding abnormalities or men who are taking medications that thin the blood, such as heparin or warfarin
• Men with penile implants

Injected Alprostadil. Injected alprostadil (Caverject, Edex) employs a very small needle that the man injects into the erectile tissue of his penis. About 80% of men describe the pain of administering the injection as being very mild. Edex is a newer and less expensive form of injected alprostadil. In one 12-month study of 894 patients, Edex injections achieved erections in 95% of attempts.

The drug should not be injected more than 3 times a week or more than once within a 24-hour period.

MUSE System. The MUSE system delivers alprostadil through the urethra. It works in the following way:

• The device is a thin plastic tube with a button at the top.
• The man inserts the tube into his urethral opening right after urination. (Urinating or urine leakage right after administration may reduce the amount of medication.)
• He presses the button, which releases a pellet containing alprostadil.
• The man rolls his penis between his hands for 10 to 30 seconds to evenly distribute the drug. To avoid discomfort, the man should keep the penis as straight as possible during administration.
• The man should be upright, either sitting, standing or walking for about 10 minutes after administration. By that time, he should have achieved an erection that lasts between 30 to 60 minutes. (If a man lies on his back too soon after administration, blood flow to the penis may decrease and the erection may be lost.)
• The erection may continue after orgasm.

The MUSE system should not be used more than twice a day and is not appropriate for men with abnormal penis anatomy.

Side Effects of Most Alprostadil Methods . Certain side effects are common to all methods of administration, although they may differ in severity depending on how the drug is given:

• Pain and burning at the application site. In one study half of the men who injected alprostadil experienced some burning and pain at the injection site.
• Scarring of the penis (Peyronie's disease), which is most likely to occur with injections.
• Sudden, low blood pressure. Symptoms include dizziness, lightheadedness, and fainting. If these symptoms occur, the man should lie down immediately with his legs raised.
• Priapism (prolonged erection). Possible with any method, but less chance with the MUSE system than with injections. If priapism occurs, applying ice for 10-minute periods to the inner thigh may help reduce blood flow. Erections that last 4 hours or longer require emergency care.
• Women partners may experience vaginal burning or itching. The drug may have toxic effects if it reaches the fetus in pregnant women, so men should not use alprostadil for intercourse with pregnant women without the use of a condom or other barrier contraceptive device.
• Other side effects. Other side effects include minor bleeding or spotting, redness in the penis, and aching in the testicles, legs, and area around the anus.

Injections Using Papaverine and Phentolamine

Until the introduction of alprostadil, the two drugs used for injection therapy had been papaverine (Pavabid, Cerespan) and phentolamine (Regitine). Adverse reactions are usually minor but include pain, ulcers, and prolonged erections (priapism).

Testosterone Replacement Therapy

Testosterone replacement therapy may be helpful for some men, particularly those with hypogonadism. Forms of testosterone therapy include:

• Muscle injections using testosterone enanthate (Andryl, Delatestryl) or cypionate (Andro-Cyp, Depo-Testosterone, Virion). This has been the standard administration.
• Skin patch (Testoderm, Testoderm TTS, Androderm). Depending on the brand, patches may be applied to the skin of the scrotum every 24 hours or to the abdomen, back, thighs, or upper arm. In the latter case, two patches are required every 24 hours. Testoderm and Testoderm TTS may cause less skin irritation than Androderm.
• Skin gel (Androgel, Testim). At this time, the gel is applied only to the same parts of the body as the patch. A gel applied to the penile skin is being investigated for men with hypogonadism and erectile dysfunction. Pregnant women must avoid contact with the gel because theoretically the testosterone could harm the fetus.

Oral forms of testosterone are not recommended because of the risk for liver damage when taken for long periods of time.

Testosterone replacement is used or investigated in the following:

• Replacement Therapy for Hypogonadism. Testosterone replacement therapy may be effective in inducing puberty in adolescent boys with hypogonadism and may also be helpful for some adult patients with the condition. Either the skin patch or gel achieves normal testosterone levels in 67 - 90% of men. The gel is proving to be more effective than the patch at improving sexual desire and well being. It may also be more effective in boosting energy and mood and increasing muscle mass and weight in men with testosterone deficiencies.
• Replacement for Older Men with Androgen Deficiencies. Some experts believe testosterone replacement therapy may be helpful for older men whose androgen (male hormone) levels are deficient.
• Testosterone in Men with Normal Levels. Testosterone therapy is not recommended for men with testosterone levels that are normal for their age group. One 2003 study did report that short-term (one-month) use of the patch in men with low-normal testosterone levels improved their response to sildenafil (Viagra).

There is some concern that replacement therapy may increase the risk for the following adverse effects, particularly in men with normal testosterone levels:

• Lower HDL (the so-called good cholesterol)
• Rapid growth of prostate tumors in men with existing prostate cancers. (Taking testosterone does not appear to increase the risk for prostate cancer, but experts remain concerned.)
• Lower sperm count
• Possible cause of sleep apnea
• Possible increased risk for polycythemia, an abnormal increase in red blood cells
• Possible increased risk for benign prostatic hyperplasia

In men with normal male hormone levels, replacement therapy also does not appear to improve bone mass or muscle strength.

• Review Date: 6/27/2006
• Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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