Erectile dysfunction (impotence) is the inability to achieve or maintain an erection adequate for penetration.

• The cause may be a disorder that reduces blood flow or damages nerves to the penis, a hormonal disorder, use of certain drugs, or psychologic issues.
• In many men, sex drive (libido) also decreases.
• A physical examination (including blood pressure measurement), blood tests, erection testing during sleep, and sometimes ultrasonography may detect a disorder contributing to erectile dysfunction.
• Drugs, taken by mouth or inserted or injected into the penis, may help, as may constriction and vacuum devices and psychologic therapy.

Every man is occasionally unable to achieve an erection, which is normal. Erectile dysfunction occurs when the problem is frequent or continual.

Erectile dysfunction can range from mild to severe. A man with mild erectile dysfunction may occasionally achieve a full erection, but more often he achieves an erection that is inadequate for penetration or no erection at all. A man with severe erectile dysfunction is rarely able to achieve an erection.

Erectile dysfunction becomes more common with age but is not part of the normal aging process. About half of men 65 years of age and three fourths of men 80 years of age have erectile dysfunction.

Causes

To achieve an erection, the penis needs an adequate inflow of blood, a slowing of blood outflow, and proper function of nerves leading to and from the penis.

Disorders that narrow arteries and decrease blood inflow (such as atherosclerosis, diabetes, high blood pressure, and high blood cholesterol levels) or surgery affecting the blood vessels can cause erectile dysfunction. Also, abnormalities in the veins of the penis can sometimes drain blood back to the body so rapidly that erections cannot be sustained despite adequate blood inflow.

Damage to the nerves that lead to or from the penis can produce erectile dysfunction. Such damage could result from pelvic or abdominal surgery (particularly prostate surgery), radiation therapy, spinal disease, diabetes, multiple sclerosis, or peripheral nerve disorders.

Other risk factors include stroke, smoking, alcohol, and drugs. Drugs that commonly cause erectile dysfunction (particularly in older men) include antihypertensives, antidepressants, some sedatives, cimetidine, digoxin, some diuretics, antipsychotics, and illicit drugs.

Occasionally, hormonal disturbances (such as abnormally low levels of testosterone) cause erectile dysfunction. Also, factors that decrease a man's energy level (such as illness, fatigue, and stress) can make it difficult to achieve an erection.

Psychologic issues that can cause sexual dysfunction (see Sexual Dysfunction in Men: Psychologic Causes of Sexual Dysfunction) can impair the ability to achieve erections. Psychologic causes are more common in younger men. Any new stressful situation, such as a change of sex partners or problems with relationships or at work, can also contribute.

Did You Know... Occasional inability to achieve an erection is normal and does not mean that a man has erectile dysfunction. About half of men older than 65 and one fourth of men older than 80 can usually have erections adequate for penetration. Low levels of testosterone tend to decrease sex drive rather than cause erectile dysfunction. Combinations of drugs injected into the penis and devices that constrict or apply suction to the penis are highly effective and lack many of the side effects of oral drugs. Psychologic therapies can help even when erectile dysfunction has a physical cause.

Symptoms

Sex drive (libido) often decreases in men with erectile dysfunction, although some men do maintain a normal libido. Regardless of whether libido changes, men with erectile dysfunction have difficulty engaging in intercourse either because the erect penis is not sufficiently hard, long, or elevated for penetration or because the erection cannot be sustained. Some men stop having erections during sleep or upon awakening. Others may attain strong erections sometimes but be unable to attain or maintain erections other times.

When testosterone levels are low, the result is more likely to be a drop in libido than erectile dysfunction. In addition, low testosterone levels may lead to thinning of the bones, loss of energy, and loss of muscle mass.

Diagnosis

To diagnose the cause of erectile dysfunction, a doctor asks about diseases and conditions that may contribute to erectile dysfunction and drugs the man is taking. A general physical examination, including examination of the genital organs and prostate, is performed. The doctor may assess the function of nerves that supply the genitals. Measuring the blood pressure in the legs and assessing the pulses in the legs and feet may reveal a problem with the arteries that supply blood to the penis.

A blood sample can be taken to measure the level of testosterone. Certain blood tests can help identify diseases that may lead to temporary or permanent erectile dysfunction, such as diabetes or infection.

If a problem with the arteries or veins is suspected, specialized tests may be done. For example, a device can be used at home to measure erections during sleep (when they normally occur). If erections are present during sleep, the cause may be mostly psychologic, whereas if erections are absent during sleep, the cause may be mostly physical. Ultrasonography also can be used to measure blood flow to the penis.

Treatment

Measures that help prevent or control conditions that contribute to erectile dysfunction, such as high blood pressure, atherosclerosis, and diabetes, may also help improve erectile dysfunction, although the effect may be small. For example, losing excess weight, exercising, and stopping smoking may help. Some men and their partners may choose not to pursue any treatment for erectile dysfunction. Physical contact without an erection may satisfy their needs for intimacy and fulfillment.

Sometimes, stopping use of a particular drug can improve erections.

Several folk remedies for erectile dysfunction exist, but none have proven to be effective.

For men who choose to pursue treatment, there are many choices.

Drug Treatment: Many drugs are used to treat erectile dysfunction. Most drugs that are given to treat erectile dysfunction increase blood flow to the penis. Most of these drugs are given by mouth, but some drugs can be applied locally—by injection or insertion into the penis.

Sildenafil, vardenafil, and tadalafil are known as phosphodiesterase inhibitors. These are the drugs most frequently used to treat erectile dysfunction. They are effective in about 60 to 75% of men with erectile dysfunction. These drugs are taken by mouth about 1 hour before sexual activity. Tadalafil is effective for about a day, longer than sildenafil and vardenafil, which are effective for about 4 to 6 hours. The drugs are effective only when the man is sexually aroused. Side effects of phosphodiesterase inhibitors include headache, flushing, stuffy nose, upset stomach, and vision problems. More serious side effects, including dangerously low blood pressure, can occur when phosphodiesterase inhibitors are taken with certain other drugs (such as nitroglycerin or amyl nitrite). Because of this risk, men should not take phosphodiesterase inhibitors if they take nitroglycerin. Rarely, men taking these drugs have experienced blindness, although it is possible that blindness had nothing to do with taking the drug. Phosphodiesterase inhibitors can cause painful, prolonged erections, but this occurs very rarely.

Other oral drugs that have been used to treat erectile dysfunction are phentolamine, yohimbine, and testosterone. They have only limited effectiveness and can have significant side effects.

Drugs injected or inserted into the penis widen the arteries and increase blood flow to the penis. Men who cannot tolerate drugs taken by mouth can often be treated with these drugs. An example is alprostadil, in the form of a pellet (suppository), which can be inserted into the penis through the urethra. It may cause light-headedness, a burning sensation of the penis, or, occasionally, a prolonged, painful erection (priapism—see Penile and Testicular Disorders: Priapism). Because these serious side effects occasionally occur, a man usually takes his first dose under observation in a doctor's office.

A man can also induce an erection by injecting drugs (such as alprostadil alone or a combination of alprostadil, papaverine, and phentolamine) into the shaft of his penis. Injection is one of the most effective ways to obtain an erection, producing erections in 80 to 90% of men with erectile dysfunction. However, many men are unwilling to inject their penis. Also, the injection is sometimes painful and occasionally causes priapism, and repeated injections may eventually produce scar tissue.

Testosterone replacement therapy may help men whose erectile dysfunction is caused by abnormally low testosterone levels. Unlike other drugs, which work by increasing blood flow to the penis, testosterone works by correcting a hormonal deficiency. Testosterone can be taken in many forms, including patches, topical creams, and injections. Side effects can include liver dysfunction, increased red blood cell counts, and increased risk of stroke. Testosterone replacement alone is rarely adequate to restore erectile function. Whether testosterone increases risk of prostate cancer is unclear, but men taking testosterone should be closely monitored.

Constriction (binding) and Vacuum Devices: Erectile dysfunction can often be managed with the use of a constriction device with or without a vacuum device. These devices enable a man to avoid the side effects that can occur with drug treatment. Constriction devices are among the least expensive treatments for erectile dysfunction. These devices (such as bands and rings made of metal, rubber, or leather) are placed at the base of the penis to slow the outflow of blood. These medically engineered devices can be purchased with a doctor's prescription in a pharmacy, but inexpensive versions (often called cock rings) can be purchased in stores that sell sexual paraphernalia. However, the devices are somewhat cumbersome and can cause penile pain, difficulty ejaculating, and bruising. Constriction devices should not be left on for longer than 30 minutes, or they may cause skin breakdown (ulceration).

Vacuum devices (which consist of a hollow chamber attached to a source of suction) fit over the penis, creating a seal. Mechanical suction applied to the chamber draws blood into the penis, producing an erection. Many vacuum devices have a constriction device that attaches to the base of the penis. If not, a constriction device can be applied separately.

Surgery: When erectile dysfunction does not respond to other treatments, a device that simulates an erection (prosthesis) can be surgically implanted in the penis.

A variety of prostheses are available. One type consists of a pair of firm rods, one inserted into each of the corpora cavernosa to create a permanently hard penis. Another prosthesis type is an inflatable balloon that is inserted into the penis. Before having intercourse, the man inflates the balloon with a small internal pump. Surgical implantation of a penile prosthesis requires at least a brief hospital stay and a 6-week recovery before intercourse is attempted.

Psychologic Therapy: Some types of psychologic therapy (which include behavior-modification techniques, such as the sensate focus technique—see Sexual Dysfunction: Sex Therapy: Sensate Focus Technique) can improve the mental and emotional factors that contribute to erectile dysfunction. Psychologic therapy can even help when the erectile dysfunction has a physical cause, because psychologic factors often compound the problem.

Specific therapies are selected based on the particular psychologic cause of the man's erectile dysfunction. For example, if the man is suffering from depression, psychotherapy may help with erectile dysfunction. Antidepressants may help erectile dysfunction by relieving depression, but antidepressants may themselves decrease libido and contribute to erectile dysfunction, so their effect may be difficult to predict. Sometimes psychotherapy can reduce anxiety about sexual performance in men with erectile dysfunction from any cause. Improvement may take a long time, and many sessions are usually required. A man, and often his partner, must be highly motivated for psychotherapy to work.

Last full review/revision September 2007 by Fran E. Kaiser, MD