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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.
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.
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.
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.
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.
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.
FDA has approved sildenafil, the first oral tablet to treat erectile dysfunction (ED). Taken about an hour before anticipated sexual activity, sildenafil enhances the response to sexual stimulation. It led to at least some improvement in 7 out of 10 men with ED compared with 2 out of 10 who improved on placebo.
In clinical studies, sildenafil was assessed for its effect on the ability of men with ED to engage in sexual activity and in many cases specifically on their ability to achieve and maintain an erection sufficient for satisfactory sexual activity. It was evaluated primarily at doses of 25 mg, 50 mg, and 100 mg in 21 randomized, double-blind, placebo-controlled trials of up to 6 months in duration. Sildenafil was administered to more than 3,000 patients aged 19 to 87 years, with ED of various etiologies (organic, psychogenic, mixed) with a mean duration of 5 years. The drug demonstrated statistically significant improvement compared with placebo in all 21 studies.
The first in a new class of medications, sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Physiologically, sexual stimulation causes local release of nitric oxide (NO) in the corpus caver-nosum. NO then activates the enzyme guanylate cyclase, which results in increased levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil enhances the effect of NO by inhibiting PDE5, which is responsible for degradation of cGMP in the corpus cavernosum.
Sildenafil was effective in a broad range of ED patients, including those whose ED arose from diabetes mellitus, spinal cord injury, transurethral resection of the prostate, or no known physical cause. It was used in patients with a history of coronary artery disease, hypertension, peripheral vascular disease, depression, or coronary artery bypass graft, and in patients taking various drugs, including antidepressants/antipsychotics and antihypertensives/diuretics.
For most patients, the recommended dose is 50 mg, taken as needed approximately 1 hour before sexual activity. However, the drug may be taken anywhere from one-half hour to 4 hours before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. The maximum recommended dosing frequency is once a day. Sildenafil was shown to potentiate the hypotensive effects of nitrates, and its administration in patients who use various nitrates in any form is therefore contraindicated.
Sildenafil's side effects, when they occur, are usually mild and temporary. The most common side effects reported in clinical trials included headache, flushing, and upset stomach. Visual changes, such as mild and temporary changes in blue/green color perception or increased sensitivity to light, can occur.
A thorough medical history and physical examination should be undertaken to diagnose ED, determine potential underlying causes, and identify appropriate treatment.There is a degree of cardiac risk associated with sexual activity; therefore, physicians may wish to consider the cardiovascular status of their patients prior to initiating any treatment for ED.
Sildenafil is manufactured by Pfizer Pharmaceuticals, New York, NY, and marketed under the trade name Viagra. The company reported to FDA on May 21, 1998, that it learned of the deaths of six people who had taken sildenafil. FDA is investigating these reports and will continue to monitor any other serious adverse event reports to determine if any changes exist in this drug's safety profile. The label states that Viagra and the concomitant administration of nitroglycerin or other organic nitrates is contraindicated.
FDA's clinical review of the studies, approval letter, and labeling (package insert) can be found on the Internet at http://www.fda.gov/cder/news/viagra.htm.
REPORT SERIOUS ADVERSE EVENTS AND PRODUCT PROBLEMS TO MEDWATCH
1-800-FDA-1088
Source for Viagra topic above: FDA Medical Bulletin * Summer 1998 * Volume 28 Number 1
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.
Impotence Information Center
P.O. Box 9
Minneapolis, MN 55440
1-800-843-4315
Impotence Institute of America (IIA)
Impotence World Association
119 South Ruth Street
Maryville, TN 37803
(865) 379-2154 or 1-800-669-1603
Email: iwatenn@aol.com
Internet: http://www.impotenceworld.org/
Sexual Function Health Council
American Foundation for Urologic Disease
300 West Pratt Street
Suite 401
Baltimore, MD 21201
1-800-242-2383
The Geddings Osbon, Sr. Foundation
P.O. Drawer 1593
Augusta, GA 30903-1593
1-800-433-4215
3 Information Way
Bethesda, MD 20892-3580
E-mail: National Kidney and Urologic Diseases Information Clearinghouse
The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Public Health Service. Established in 1987, the clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to their families, health care professionals, and the public. NKUDIC answers inquiries; develops, reviews, and distributes publications; and works closely with professional and patient organizations and Government agencies to coordinate resources about kidney and urologic diseases.
Publications produced by the clearinghouse are carefully reviewed for scientific accuracy, content, and readability.
This e-text is not copyrighted. The clearinghouse encourages users of this e-pub to duplicate and distribute as many copies as desired.
NIH Publication No. 95-3923
September 1995 e-text last updated: August 2000