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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.
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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 and is surrounded by the
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.
Figure 1. Arteries (top) and veins
(bottom) penetrate the long, filled cavities running the
length of the penis--the corpora cavernosa and the corpous
sponglosum. Erection occurs when relaxed muscles allow the
corpora cavernosa to fill with excess blood fed by the
arteries, while drainage of blood through the veins is
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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
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
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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
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.
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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
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
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
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 (see figure 2).
Figure 2. A vacuum-constrictor device
causes an erection by creating a partial vacuum around the
penis, which draws blood into the corpora cavernosa. Pictured
here are the necessary components: (a) a plastic cylinder,
which covers the penis; (b) a pump, which draws air out of the
cylinder; and (c) an elastic ring, which, when fitted over the
base of the penis, traps the blood and sustains the erection
after the cylinder is removed.
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:
- to implant a device that can cause the penis to become
- to reconstruct arteries to increase flow of blood to the
- to block off veins that allow blood to leak from the penile
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.
Figure 3. With an inflatable implant,
erection is produced by squeezing a small pump (a) implanted
in a scrotum. The pump causes fluid to flow from a reservoir
(b) residing in the lower pelvis to two cylinders (c) residing
in the penis. The cylinders expand to create the
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.
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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
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.
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- Erectile dysfunction (ED) is the repeated inability to get or
keep an erection firm enough for sexual intercourse.
- ED affects 15 to 30 million American men.
- ED usually has a physical cause.
- ED is treatable at all ages.
- Treatments include psychotherapy, drug therapy, vacuum
devices, and surgery.
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Sexual Function Health
American Urological Association
American Diabetes Association
American Association of
Sex Educators, Counselors, and Therapists (AASECT)
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