Impotence is a consistent inability to sustain an erection sufficient for sexual intercourse. Medical professionals often use the term "erectile dysfunction" to describe this disorder and to differentiate it from other problems that interfere with sexual intercourse, such as lack of sexual desire and problems with ejaculation and orgasm. This fact sheet focuses on impotence defined as erectile dysfunction.
Impotence can be a total inability to achieve erection, an inconsistent ability to do so, or a tendency to sustain only brief erections. These variations make defining impotence and estimating its incidence difficult. Experts believe impotence affects between 10 and 15 million American men. In 1985, the National Ambulatory Medical Care Survey counted 525,000 doctor-office visits for erectile dysfunction.
Impotence usually has a physical cause, such as disease, injury, or drug side-effects. Any disorder that impairs blood flow in the penis has the potential to cause impotence. Incidence rises with age: about 5 percent of men at the age of 40 and between 15 and 25 percent of men at the age of 65 experience impotence. Yet, it is not an inevitable part of aging.
Impotence is treatable in all age groups, and awareness of this fact has been growing. More men have been seeking help and returning to near-normal sexual activity because of improved, successful treatments for impotence. Urologists, who specialize in problems of the urinary tract, have traditionally treated impotence--especially complications of impotence.
How Does an Erection Occur?
The penis contains two chambers, called the corpora cavernosa, which run the length of the organ (see figure 1). A spongy tissue fills the chambers. The corpora cavernosa are surrounded by a membrane, called the tunica albuginea. The spongy tissue contains smooth muscles, fibrous tissues, spaces, veins, and arteries. The urethra, which is the channel for urine and ejaculate, runs along the underside of the corpora cavernosa.
Erection begins with sensory and mental stimulation. Impulses from the brain and local nerves cause the muscles of the corpora cavernosa to relax, allowing blood to flow in and fill the open spaces. The blood creates pressure in the corpora cavernosa, making the penis expand. The tunica albuginea helps to trap the blood in the corpora cavernosa, thereby sustaining erection. Erection is reversed when muscles in the penis contract, stopping the inflow of blood and opening outflow channels.
What Causes Impotence?
Since an erection requires a sequence of events, impotence can occur when any of the events is disrupted. The sequence includes nerve impulses in the brain, spinal column, and area of the penis, and response in muscles, fibrous tissues, veins, and arteries in and near the corpora cavernosa.
Damage to arteries, smooth muscles, and fibrous tissues, often as a result of disease, is the most common cause of impotence. Diseases--including diabetes, kidney disease, chronic alcoholism, multiple sclerosis, atherosclerosis, and vascular disease--account for about 70 percent of cases of impotence. Between 35 and 50 percent of men with diabetes experience impotence.
Surgery (for example, prostate surgery) can injure nerves and arteries near the penis, causing impotence. Injury to the penis, spinal cord, prostate, bladder, and pelvis can lead to impotence by harming nerves, smooth muscles, arteries, and fibrous tissues of the corpora cavernosa.
Also, many common medicines produce impotence as a side effect. These include high blood pressure drugs, antihistamines, antidepressants, tranquilizers, appetite suppressants, and cimetidine (an ulcer drug).
Experts believe that psychological factors cause 10 to 20 percent of cases of impotence. These factors include stress, anxiety, guilt, depression, low self-esteem, and fear of sexual failure. Such factors are broadly associated with more than 80 percent of cases of impotence, usually as secondary reactions to underlying physical causes.
Other possible causes of impotence are smoking, which affects blood flow in veins and arteries, and hormonal abnormalities, such as insufficient testosterone.
How Is Impotence Diagnosed?
Medical and sexual histories help define the degree and nature of impotence. A medical history can disclose diseases that lead to impotence. A simple recounting of sexual activity might distinguish between problems with erection, ejaculation, orgasm, or sexual desire.
A history of using certain prescription drugs or illegal drugs can suggest a chemical cause. Drug effects account for 25 percent of cases of impotence. Cutting back on or substituting certain medications often can alleviate the problem.
A physical examination can give clues for systemic problems. For example, if the penis does not respond as expected to certain touching, a problem in the nervous system may be a cause. Abnormal secondary sex characteristics, such as hair pattern, can point to hormonal problems, which would mean the endocrine system is involved. A circulatory problem might be indicated by, for example, an aneurysm in the abdomen. And unusual characteristics of the penis itself could suggest the root of the impotence--for example, bending of the penis during erection could be the result of Peyronie's disease.
Several laboratory tests can help diagnose impotence. Tests for systemic diseases include blood counts, urinalysis, lipid profile, and measurements of creatinine and liver enzymes. For cases of low sexual desire, measurement of testosterone in the blood can yield information about problems with the endocrine system.
Monitoring erections that occur during sleep (nocturnal penile tumescence) can help rule out certain psychological causes of impotence. Healthy men have involuntary erections during sleep. If nocturnal erections do not occur, then the cause of impotence is likely to be physical rather than psychological. Tests of nocturnal erections are not completely reliable, however. Scientists have not standardized such tests and have not determined when they should be applied for best results.
A psychosocial examination, using an interview and questionnaire, reveals psychological factors. The man's sexual partner also may be interviewed to determine expectations and perceptions encountered during sexual intercourse.
How Is Impotence Treated?
Most physicians suggest that treatments for impotence proceed along a path moving from least invasive to most invasive. This means cutting back on any harmful drugs is considered first. Psychotherapy and behavior modifications are considered next, followed by vacuum devices, oral drugs, locally injected drugs, and surgically implanted devices (and, in rare cases, surgery involving veins or arteries).
Experts often treat psychologically based impotence using techniques that decrease anxiety associated with intercourse. The patient's partner can help apply the techniques, which include gradual development of intimacy and stimulation. Such techniques also can help relieve anxiety when physical impotence is being treated.
Drugs for treating impotence can be taken orally, injected directly into the penis, or inserted into the urethra at the tip of the penis. In March 1998, the Food and Drug Administration approved sildenafil citrate (marketed as Viagra), the first oral pill to treat impotence. Taken 1 hour before sexual activity, sildenafil works by enhancing the effects of nitric oxide, a chemical that relaxes smooth muscles in the penis during sexual stimulation, allowing increased blood flow. While sildenafil improves the response to sexual stimulation, it does not trigger an automatic erection as injection drugs do. The recommended dose is 50 mg, and the physician may adjust this dose to 100 mg or 25 mg, depending on the needs of the patient. The drug should not be used more than once a day.
Oral testosterone can reduce impotence in some men with low levels of natural testosterone. Patients also have claimed effectiveness of other oral drugs--including yohimbine hydrochloride, dopamine and serotonin agonists, and trazodone--but no scientific studies have proved the effectiveness of these drugs in relieving impotence. Some observed improvements following their use may be examples of the placebo effect, that is, a change that results simply from the patient's believing that an improvement will occur.
Many men gain potency by injecting drugs into the penis, causing it to become engorged with blood. Drugs such as papaverine hydrochloride, phentolamine, and alprostadil (marked as Caverject) widen blood vessels. These drugs may create unwanted side effects, however, including persistent erection (known as priapism) and scarring. Nitroglycerin, a muscle relaxant, sometimes can enhance erection when rubbed on the surface of the penis.
A system for inserting a pellet of alprostadil into the urethra is marketed as MUSE. The system uses a pre-filled applicator to deliver the pellet about an inch deep into the urethra at the tip of the penis. An erection will begin within 8 to 10 minutes and may last 30 to 60 minutes. The most common side effects of the preparation are aching in the penis, testicles, and area between the penis and rectum; warmth or burning sensation in the urethra; redness of the penis due to increased blood flow; and minor urethral bleeding or spotting.
Research on drugs for treating impotence is expanding rapidly. Patients should ask their doctors about the latest advances.
Mechanical vacuum devices cause erection by creating a partial vacuum around the penis, which draws blood into the penis, engorging it and expanding it. The devices have three components: a plastic cylinder, in which the penis is placed; a pump, which draws air out of the cylinder; and an elastic band, which is placed around the base of the penis, to maintain the erection after the cylinder is removed and during intercourse by preventing blood from flowing back into the body (see figure 2).
One variation of the vacuum device involves a semirigid rubber sheath that is placed on the penis and remains there after attaining erection and during intercourse.
Surgery usually has one of three goals:
Implanted devices, known as prostheses, can restore erection in many men with impotence. Possible problems with implants include mechanical breakdown and infection. Mechanical problems have diminished in recent years because of technological advances.
- to implant a device that can cause the penis to become erect;
- to reconstruct arteries to increase flow of blood to the penis;
- to block off veins that allow blood to leak from the penile tissues.
Malleable implants usually consist of paired rods, which are inserted surgically into the corpora cavernosa, the twin chambers running the length of the penis. The user manually adjusts the position of the penis and, therefore, the rods. Adjustment does not affect the width or length of the penis.
Inflatable implants consist of paired cylinders, which are surgically inserted inside the penis and can be expanded using pressurized fluid (see figure 3). Tubes connect the cylinders to a fluid reservoir and pump, which also are surgically implanted. The patient inflates the cylinders by pressing on the small pump, located under the skin in the scrotum. Inflatable implants can expand the length and width of the penis somewhat. They also leave the penis in a more natural state when not inflated.
Surgery to repair arteries can reduce impotence caused by obstructions that block the flow of blood to the penis. The best candidates for such surgery are young men with discrete blockage of an artery because of an injury to the crotch area or fracture of the pelvis. The procedure is less successful in older men with widespread blockage.
Surgery to veins that allow blood to leave the penis usually involves an opposite procedure--
intentional blockage. Blocking off veins (ligation) can reduce the leakage of blood that diminishes rigidity of the penis during erection. However, experts have raised questions about this procedure's long-term effectiveness.
What Will the Future Bring?
Advances in suppositories, injectable medications, implants, and vacuum devices have expanded the options for men seeking treatment for impotence. These advances also have helped increase the number of men seeking treatment.
An oral form of the drug phentolamine may soon join sildenafil in the armamentarium of noninvasive treatments for impotence. Other treatments in the experimental stages include reconstruction surgery for damaged veins and arteries in the penis. Whether or not this method proves to be safe and effective, ongoing improvements in traditional methods should continue to create more successful and widespread treatment of impotence.
Points to Remember
- Impotence is a consistent inability to sustain an erection sufficient for sexual intercourse.
- Impotence affects 10 to 15 million American men.
- Impotence usually has a physical cause.
- Impotence is treatable in all age groups.
- Treatments include psychotherapy, drug therapy, vacuum devices, and surgery.
Resources for More Information
Impotence Information Center
P.O. Box 9
Minneapolis, MN 55440
Sexual Function Health Council
American Foundation for Urologic Disease
300 West Pratt Street
Baltimore, MD 21201
The Geddings Osbon, Sr. Foundation
P.O. Drawer 1593
Augusta, GA 30903-1593
National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
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NIH Publication No. 95-3923
e-text last updated: August 2000