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Erectile dysfunction, sometimes called "impotence," is the repeated inability
to get or keep an erection firm enough for sexual intercourse. The word
"impotence" may also be used to describe other problems that interfere with
sexual intercourse and reproduction, such as lack of sexual desire and problems
with ejaculation or orgasm. Using the term erectile dysfunction makes it clear
that those other problems are not involved. Erectile dysfunction, or ED, 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 ED and estimating its incidence difficult.
Estimates range from 15 million to 30 million, depending on the definition used.
According to the National Ambulatory Medical Care Survey (NAMCS), for every
1,000 men in the United States, 7.7 physician office visits were made for ED in
1985. By 1999, that rate had nearly tripled to 22.3. The increase happened
gradually, presumably as treatments such as vacuum devices and injectable drugs
became more widely available and discussing erectile function became accepted.
Perhaps the most publicized advance was the introduction of the oral drug
sildenafil citrate (Viagra) in March 1998. NAMCS data on new drugs show an
estimated 2.6 million mentions of Viagra at physician office visits in 1999, and
one-third of those mentions occurred during visits for a diagnosis other than
ED. In older men, ED usually has a physical cause, such as disease, injury, or
side effects of drugs. Any disorder that causes injury to the nerves or impairs
blood flow in the penis has the potential to cause ED. Incidence increases with
age: About 5 percent of 40-year-old men and between 15 and 25 percent of
65-year-old men experience ED. But it is not an inevitable part of aging. ED is treatable at any age, and awareness of this fact has been growing. More
men have been seeking help and returning to normal sexual activity because of
improved, successful treatments for ED. Urologists, who specialize in problems
of the urinary tract, have traditionally treated ED; however, urologists
accounted for only 25 percent of Viagra mentions in 1999. The penis contains two chambers called the corpora cavernosa, which run the
length of the organ. 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 and is surrounded by the corpus spongiosum. Erection begins with sensory or mental stimulation, or both. Impulses from
the brain and local nerves cause the muscles of the corpora cavernosa to relax,
allowing blood to flow in and fill the spaces. The blood creates pressure in the
corpora cavernosa, making the penis expand. The tunica albuginea helps trap the
blood in the corpora cavernosa, thereby sustaining erection. When muscles in the
penis contract to stop the inflow of blood and open outflow channels, erection
is reversed.
Since an erection requires a precise sequence of events, ED can occur when
any of the events is disrupted. The sequence includes nerve impulses in the
brain, spinal column, and area around the penis, and response in muscles,
fibrous tissues, veins, and arteries in and near the corpora cavernosa. Damage to nerves, arteries, smooth muscles, and fibrous tissues, often as a
result of disease, is the most common cause of ED. Diseases--such as diabetes,
kidney disease, chronic alcoholism, multiple sclerosis, atherosclerosis,
vascular disease, and neurologic disease--account for about 70 percent of ED
cases. Between 35 and 50 percent of men with diabetes experience ED. Also, surgery (especially radical prostate and bladder surgery for cancer)
can injure nerves and arteries near the penis, causing ED. Injury to the penis,
spinal cord, prostate, bladder, and pelvis can lead to ED by harming nerves,
smooth muscles, arteries, and fibrous tissues of the corpora cavernosa. In addition, many common medicines--blood pressure drugs, antihistamines,
antidepressants, tranquilizers, appetite suppressants, and cimetidine (an ulcer
drug)--can produce ED as a side effect. Experts believe that psychological factors such as stress, anxiety, guilt,
depression, low self-esteem, and fear of sexual failure cause 10 to 20 percent
of ED cases. Men with a physical cause for ED frequently experience the same
sort of psychological reactions (stress, anxiety, guilt, depression). Other possible causes are smoking, which affects blood flow in veins and
arteries, and hormonal abnormalities, such as not enough testosterone. Medical and sexual histories help define the degree and nature of ED. A
medical history can disclose diseases that lead to ED, while a simple recounting
of sexual activity might distinguish among problems with sexual desire,
erection, ejaculation, or orgasm. Using certain prescription or illegal drugs can suggest a chemical cause,
since drug effects account for 25 percent of ED cases. Cutting back on or
substituting certain medications can often alleviate the problem. A physical examination can give clues to systemic problems. For example, if
the penis is not sensitive to touching, a problem in the nervous system may be
the cause. Abnormal secondary sex characteristics, such as hair pattern or
breast enlargement, can point to hormonal problems, which would mean that the
endocrine system is involved. The examiner might discover a circulatory problem
by observing decreased pulses in the wrist or ankles. And unusual
characteristics of the penis itself could suggest the source of the problem--for
example, a penis that bends or curves when erect could be the result of
Peyronie's disease. Several laboratory tests can help diagnose ED. Tests for systemic diseases
include blood counts, urinalysis, lipid profile, and measurements of creatinine
and liver enzymes. Measuring the amount of free testosterone in the blood can
yield information about problems with the endocrine system and is indicated
especially in patients with decreased sexual desire. Monitoring erections that occur during sleep (nocturnal penile tumescence)
can help rule out certain psychological causes of ED. Healthy men have
involuntary erections during sleep. If nocturnal erections do not occur, then ED
is likely to have a physical rather than psychological cause. 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 a questionnaire, reveals
psychological factors. A man's sexual partner may also be interviewed to
determine expectations and perceptions during sexual intercourse. Most physicians suggest that treatments proceed from least to most invasive.
Cutting back on any drugs with harmful side effects is considered first. For
example, drugs for high blood pressure work in different ways. If you think a
particular drug is causing problems with erection, tell your doctor and ask
whether you can try a different class of blood pressure medicine. Psychotherapy and behavior modifications in selected patients are considered
next if indicated, followed by oral or locally injected drugs, vacuum devices,
and surgically implanted devices. In rare cases, surgery involving veins or
arteries may be considered. Experts often treat psychologically based ED using techniques that decrease
the anxiety associated with intercourse. The patient's partner can help with the
techniques, which include gradual development of intimacy and stimulation. Such
techniques also can help relieve anxiety when ED from physical causes is being
treated. Drugs for treating ED 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 (FDA) approved Viagra, the first
pill to treat ED. In August 2003, the FDA gave approval to a second oral
medicine, vardenafil hydrochloride (Levitra). Additional oral medicines are
being tested for safety and effectiveness. Taken an hour before sexual activity, Viagra and Levitra work by enhancing
the effects of nitric oxide, a chemical that relaxes smooth muscles in the penis
during sexual stimulation and allows increased blood flow. While oral medicines improve the response to sexual stimulation, they do not
trigger an automatic erection as injections do. The recommended dose for Viagra
is 50 mg, and the physician may adjust this dose to 100 mg or 25 mg, depending
on the patient. The recommended dose for Levitra is 10 mg, and the physician may
adjust this dose to 20 mg if 10 mg is insufficient. Lower doses of 5 mg and 2.5
mg are available for patients who take other medicines or have conditions that
may decrease the body's ability to use Levitra. Neither Viagra nor Levitra should be used more than once a day. Men who take
nitrate-based drugs such as nitroglycerin for heart problems should not use
either drug because the combination can cause a sudden drop in blood pressure.
Also, Levitra should not be taken with any of the drugs called alpha-blockers,
which are used to treat prostate enlargement or high blood pressure. Oral testosterone can reduce ED in some men with low levels of natural
testosterone, but it is often ineffective and may cause liver damage. Patients
also have claimed that other oral drugs--including yohimbine hydrochloride,
dopamine and serotonin agonists, and trazodone--are effective, but the results
of scientific studies to substantiate these claims have been inconsistent.
Improvements observed following use of these drugs 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 achieve stronger erections by injecting drugs into the penis,
causing it to become engorged with blood. Drugs such as papaverine
hydrochloride, phentolamine, and alprostadil (marketed 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, can sometimes enhance erection when rubbed on the penis. A system for inserting a pellet of alprostadil into the urethra is marketed
as Muse. The system uses a prefilled applicator to deliver the pellet about an
inch deep into the urethra. An erection will begin within 8 to 10 minutes and
may last 30 to 60 minutes. The most common side effects are aching in the penis,
testicles, and area between the penis and rectum; warmth or burning sensation in
the urethra; redness from increased blood flow to the penis; and minor urethral
bleeding or spotting. Research on drugs for treating ED is expanding rapidly. Patients should ask
their doctor about the latest advances. Mechanical vacuum devices cause erection by creating a partial vacuum, which
draws blood into the penis, engorging and expanding it. The devices have three
components: a plastic cylinder, into 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
One variation of the vacuum device involves a semirigid rubber sheath that is
placed on the penis and remains there after erection is attained and during
intercourse. Surgery usually has one of three goals: Implanted devices, known as prostheses, can restore erection in many men with
ED. Possible problems with implants include mechanical breakdown and infection,
although 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 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 a pump, which
are also 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 ED caused by obstructions that block
the flow of blood. The best candidates for such surgery are young men with
discrete blockage of an artery because of an injury to the crotch or fracture of
the pelvis. The procedure is almost never 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 the rigidity of the penis during
erection. However, experts have raised questions about the long-term
effectiveness of this procedure, and it is rarely done. [Top] Advances in suppositories, injectable medications, implants, and vacuum
devices have expanded the options for men seeking treatment for ED. These
advances have also helped increase the number of men seeking treatment. Gene
therapy for ED is now being tested in several centers and may offer a
long-lasting therapeutic approach for ED. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
sponsors programs aimed at understanding the causes of erectile dysfunction and
finding treatments to reverse its effects. NIDDK's Division of Kidney, Urologic,
and Hematologic Diseases supported the researchers who developed Viagra and
continue to support basic research into the mechanisms of erection and the
diseases that impair normal function at the cellular and molecular levels,
including diabetes and high blood pressure. [Top] [Top] Sexual Function Health Council American Urological Association AUA can refer you to a urologist in your area. American Diabetes Association (ADA) ADA can help you find a doctor who specializes in diabetes care in your
area. American Association of Sex Educators, Counselors, and Therapists
(AASECT) Check the AASECT website to find a certified sexuality educator, counselor,
or therapist in your area. [Top] The U.S. Government does not endorse or favor any specific commercial product
or company. Trade, proprietary, or company names appearing in this document are
used only because they are considered necessary in the context of the
information provided. If a product is not mentioned, this does not mean or imply
that the product is unsatisfactory.
3 Information Way 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. Department of Health and Human Services. 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
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 by both
NIDDK scientists and outside experts. This fact sheet was reviewed by Arnold
Melman, M.D., Montefiore Medical Center, Bronx, NY; and Mark Hirsch, M.D., U.S.
Food and Drug Administration. This e-text is not copyrighted. The clearinghouse encourages users of this
e-pub to duplicate and distribute as many copies as desired. More Coming
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