Erectile Dysfunction
 

National Kidney and Urologic Diseases Information Clearinghouse 

U.S. Department 

of Health and 

Human Services 

NATIONAL 

INSTITUTES 

OF HEALTH 

What is erectile dysfunction 

(ED)? 

ED is the inability to get or keep an erection 

firm enough for sexual intercourse. ED can 

be a total inability to achieve an erection, an 

inconsistent ability to do so, or a tendency to 

sustain only brief erections. 

ED is sometimes called impotence, but that 

word is being used less often so that it will not 

be confused with other, nonmedical meanings 

of the term. 

The National Institutes of Health estimates 

that ED affects as many as 30 million men in 

the United States.1 Incidence increases with 

age: About 4 percent of men in their 50s and 

nearly 17 percent of men in their 60s experience a total inability to achieve an erection. 

The incidence jumps to 47 percent for men 

older than 75.2 But ED is not an inevitable 

part of aging. ED is treatable at any age. 

How does an erection occur? 

Two chambers called the corpora cavernosa 

run the length of the penis (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, fi brous 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. 

1National Institutes of Health (NIH) Consensus 

Conference. NIH Consensus Development Panel 

on Impotence. Impotence. Journal of the American 

Medical Association. 1993;270:83–90. 

2Saigal CS, Wessells H, Wilt T. Predictors and 

prevalence of erectile dysfunction in a racially 

diverse population. Archives of Internal Medicine. 

2006;166:207–212. 

An 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 fl ow 

in through the arteries 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 the erection. 

The erection ends when muscles in the penis 

contract to stop the inflow of blood and open 

the veins for blood outfl ow. 

Figure 1. Arteries and veins of the penis 

Corpora cavernosa 

Arteries 

Corpus spongiosum 

Corpora cavernosa 

Corpus spongiosum 

Veins 

Arteries (top) and veins (bottom) penetrate the 

corpora cavernosa and the corpus spongiosum. 

An 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 

blocked by the tunica albuginea. 
What causes ED? 

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. 

Because 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, high blood pressure, nerve 

disease or nerve damage, multiple sclerosis, 

atherosclerosis, and heart disease—account 

for the majority of ED cases. Patients should 

be thoroughly evaluated for these conditions 

before they begin any form of treatment 

for ED. 

Lifestyle choices that contribute to heart disease 

and vascular problems also raise the risk of ED. 

Smoking, drinking alcohol excessively, being 

overweight, and not exercising are possible 

causes of ED. 

Surgery—especially radical prostate and bladder surgery for cancer—can also 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 the fi brous tissues 

of the corpora cavernosa. 

In addition, ED can be a side effect of many 

common medicines such as blood pressure 

drugs, antihistamines, antidepressants, tranquilizers, appetite suppressants, and cimetidine, an ulcer drug. 

Psychological factors such as stress, anxiety, 

guilt, depression, low self-esteem, and fear of 

sexual failure can also cause ED. Even when 

ED has a physical cause, psychological factors 

may make the condition worse. 

Hormonal abnormalities, such as low levels of 

testosterone, are a less frequent cause of ED. 

How is ED diagnosed? 

Patient History 

A person’s medical and sexual histories help 

define the degree and nature of ED. The 

medical history can disclose diseases that lead 

to ED, and a simple recounting of sexual activity might identify problems with sexual desire, 

erection, ejaculation, or orgasm. 

Use of certain prescription or illegal drugs can 

suggest a chemical cause because drug effects 

are a frequent cause of ED. 

Physical Examination 

A physical examination can give clues to 

systemic problems. For example, if the penis 

is not sensitive to physical touch, a problem in 

the nervous system may be the cause. Abnormal secondary sex characteristics, such as 

unusual hair pattern or breast enlargement, 

can point to hormonal problems, which would 

mean the endocrine system is involved. The 

doctor 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. 

2 Erectile Dysfunction 
Laboratory Tests 

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 available testosterone 

in the blood can yield information about 

problems with the endocrine system and may 

explain why a patient has decreased sexual 

desire. 

Other Tests 

Monitoring erections that occur during sleep— 

nocturnal erections—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 a psychological 

cause. Tests for nocturnal erections are not 

completely reliable, however. Scientists have 

not standardized such tests and have not determined when they should be conducted for best 

results. 

Psychosocial Examination 

A psychosocial examination, using an interview 

and a questionnaire, can reveal psychological factors. A man’s sexual partner may also 

be interviewed to determine expectations and 

perceptions during sexual intercourse. 

How is ED treated? 

Most doctors suggest that treatments proceed from least to most invasive. Making a 

few healthy lifestyle changes may solve the 

problem. Quitting smoking, reducing alcohol 

consumption, losing excess weight, and increasing physical activity may help some men regain 

sexual function. 

Cutting back on or replacing medicines that 

could be causing ED is considered next. For 

example, if a patient thinks a particular blood 

pressure medicine is causing problems with 

erection, he should tell his doctor and ask 

whether he can try a different class of blood 

pressure medicine. 

Psychotherapy and behavior modifi cations 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. 

Psychotherapy 

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 during treatment for ED from physical 

causes. 

Drug Therapy 

Drugs for treating ED can be taken orally, 

injected directly into the penis, or inserted into 

the urethra at the tip of the penis. 

Oral Medications 

In March 1998, the U.S. Food and Drug 

Administration (FDA) approved sildenafi l 

(Viagra), the first pill to treat ED. Since that 

time, vardenafil hydrochloride (Levitra) and 

tadalafil (Cialis) have also been approved. 

Additional oral medicines are being tested for 

safety and effectiveness. 

Viagra, Levitra, and Cialis all belong to a class 

of drugs called phosphodiesterase (PDE) 

inhibitors. Taken an hour before sexual activity, these drugs work by enhancing the effects 

of nitric oxide, a chemical that relaxes smooth 

muscles in the penis during sexual stimulation 

and allows increased blood fl ow. 

The recommended dose for Viagra is 50 milligrams (mg), and the doctor may adjust this 

dose to 100 mg or 25 mg, depending on the 

patient. The recommended dose for either 

Levitra or Cialis is 10 mg, and the doctor may 

adjust this dose to 20 mg if 10 mg is insuffi cient. 

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 the drug. The 5 mg and 2.5 mg doses of 

Cialis are FDA-approved for daily use. 

3 Erectile Dysfunction 
None of these PDE inhibitors should be used 

more than once a day. Men who take nitratebased drugs such as nitroglycerin pills for heart 

problems should not use any of the three drugs 

because the combination can cause a sudden 

drop in blood pressure. Also, men should 

tell their doctor if they take any drugs called 

alpha-blockers, which are used to treat prostate enlargement or high blood pressure. The 

doctor may need to adjust the ED prescription. 

Taking a PDE inhibitor and an alpha-blocker 

within 4 hours of each other can cause a sudden drop in blood pressure. A small number 

of men have experienced vision or hearing loss 

after taking a PDE inhibitor. Men who experience vision or hearing loss should seek prompt 

medical attention. 

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 belief that an 

improvement will occur. 

Injectable Medications 

While oral medicines improve the response 

to sexual stimulation, they do not trigger an 

automatic erection as injections do. 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 widen 

blood vessels. The injectable form of alprostadil is marketed as Caverject. These drugs 

may create unwanted side effects, however, 

including scarring of the penis and persistent 

erection, known as priapism. Nitroglycerin 

ointment, a muscle relaxant, can sometimes 

enhance an erection when rubbed on the penis. 

A system for inserting a pellet of alprostadil 

into the urethra uses a prefi lled applicator 

to deliver the pellet about an inch into the 

urethra. The pellet form of alprostadil is marketed as MUSE. 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; a warm or burning sensation in 

the urethra; redness from increased blood fl ow 

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. 

Vacuum Devices 

Mechanical vacuum devices cause an erection by creating a partial vacuum, which draws 

blood into the corpora cavernosa, engorging 

and expanding the penis. 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 ring, 

which is moved from the end of the cylinder to 

the base of the penis as the cylinder is removed. 

The elastic ring maintains the erection during 

intercourse by preventing blood from fl owing 

back into the body (see Figure 2). The elastic ring can remain in place up to 30 minutes. 

The ring should be removed after that time to 

restore normal circulation and to avoid skin 

irritation. 

Couples may find that using a vacuum device 

requires some practice or adjustment. An 

erection achieved with a vacuum device may 

not feel like an erection achieved naturally. 

The penis may feel cold or numb and have a 

purple color. Bruising on the shaft of the penis 

may occur, but the bruises are usually painless 

and disappear in a few days. Ejaculation may 

be weakened because the elastic ring blocks 

some of the semen from traveling through the 

urethra, but the pleasure of orgasm is usually 

not affected. 

4 Erectile Dysfunction 
5 Erectile Dysfunction

Figure 2. Vacuum device

Pump

Pump

Elastic ring

A vacuum device causes an erection by creating a 

partial vacuum around the penis, which draws blood 

into the corpora cavernosa. 

Surgery

Surgery usually has one of three goals: 

penis to become erect 

• to implant a device that can cause the 

to reconstruct arteries to increase blood 

fl ow to the penis 

• 

to block off veins that allow blood to leak 

from the penile tissues 

• 

Implanted devices, known as prostheses, can 

restore erection in many men with ED. 

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.

to a fl uid reservoir and a pump, which are 

also surgically implanted. The patient infl ates 

the cylinders by pressing on the small pump, 

located under the skin in the scrotum. The 

pump causes fl uid to fl ow from a reservoir 

residing in the lower pelvis to two cylinders 

residing in the penis. Infl atable implants can 

expand the length and width of the penis to 

some degree. They also leave the penis in a 

more natural state than malleable implants do 

when not infl ated. 

Infl atable implants consist of paired cylinders, 

which are surgically inserted inside the penis 

and can be expanded using pressurized fl uid 

(see Figure 3). Tubes connect the cylinders 

Once a man has either a malleable or infl atable implant, he must use the device to have 

an erection. Possible problems with implants 

include mechanical breakdown and infection, 

although mechanical problems have decreased 

in recent years because of technological 

advances.

Figure 3. Surgical implant

Testes

Pump

Infl atable 

rods

Penis

Fluid reservoir

With an inflatable implant, an erection is produced 

by squeezing a small pump implanted in the scrotum. 

The cylinders expand to create the erection.
Surgery to repair arteries can reduce ED 

caused by obstructions that block the fl ow of 

blood. The best candidates for such surgery 

are young men with discrete blockage of an 

artery because of an injury to the groin or 

fracture of the pelvis. The procedure is usually 

unsuccessful 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, called 

ligation, can reduce the leakage of blood that 

diminishes the rigidity of the penis during an 

erection. However, experts have raised questions about the long-term effectiveness of this 

procedure, and it is rarely done. 

Points to Remember 

• 	 Erectile dysfunction (ED) is the 

inability to get or keep an erection 

firm enough for sexual intercourse. 

• 	 ED affects as many as 30 million 


American men. 


• 	 ED is usually associated with a medical condition such as diabetes, high 

blood pressure, nerve disease or nerve 

damage, multiple sclerosis, atherosclerosis, and heart disease. Patients 

should be thoroughly evaluated for 

these conditions before they begin 

any form of treatment for ED. 

• 	 Lifestyle choices that contribute to 

heart disease and vascular problems 

also raise the risk of ED. Smoking, 

drinking alcohol excessively, being 

overweight, and not exercising are 

possible causes of ED. 

• 	 ED is treatable at all ages. 

• 	 Treatments include lifestyle and medication changes, psychotherapy, drug 

therapy, vacuum devices, and surgery. 

6 Erectile Dysfunction 
7 Erectile Dysfunction

Hope through Research

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 and treating ED. The 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 an erection and the diseases 

that impair normal function at the cellular and 

molecular levels, including diabetes and high 

blood pressure.

Participants in clinical trials can play a more 

active role in their own health care, gain access 

to new research treatments before they are 

widely available, and help others by contributing to medical research. For information about 

current studies, visit www.ClinicalTrials.gov.

For More Information

American Urological Association

1000 Corporate Boulevard

Linthicum, MD 21090

Phone: 1–866–RING–AUA (1–866–746–4282) 

 or 410–689–3700

Fax: 410–689–3800

Email: aua@auanet.org

Internet: www.auanet.org

www.UrologyHealth.org

American Diabetes Association

1701 North Beauregard Street

Alexandria, VA 22311

Phone: 1–800–DIABETES (1–800–342–2383)

Fax: 703–549–6995

Email: AskADA@diabetes.org

Internet: www.diabetes.org

American Association of Sexuality Educators, 

Counselors, and Therapists

P.O. Box 1960

Ashland, VA 23005–1960

Phone: 804–752–0026

Fax: 804–752–0056

Email: aasect@aasect.org

Internet: www.aasect.org

Acknowledgments

Publications produced by the Clearinghouse 

are carefully reviewed by both NIDDK scientists and outside experts. This publication 

was originally reviewed by Arnold Melman, 

M.D., Montefi ore Medical Center, Bronx, NY, 

and Mark Hirsch, M.D., U.S. Food and Drug 

Administration.
You may also fi nd additional information about this 

topic by visiting MedlinePlus at www.medlineplus.gov.

This publication may contain information about 

medications. When prepared, this publication 

included the most current information available. 

For updates or for questions about any medications, 

contact the U.S. Food and Drug Administration 

toll-free at 1–888–INFO–FDA (1–888–463–6332) 

or visit www.fda.gov. Consult your doctor for more 

information.

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U.S. DEPARTMENT OF HEALTH 

AND HUMAN SERVICES

National Institutes of Health

NIH Publication No. 09–3923

June 2009