Erectile dysfunction (ED) affects the lives of 15 million to 30 million American men and their partners. The term erectile dysfunction covers a range of disorders, including curvature of the penis during erection (Peyronie's disease), prolonged painful erection not associated with sexual desire (priapism) and premature ejaculation. But usually it refers to the inability to obtain an adequate erection for satisfactory sexual activity.

Although erectile dysfunction is more common in men older than 65, it can occur at any age. An occasional episode of erectile dysfunction happens to most men and is perfectly normal. In fact, in most cases it's nothing to worry about. As men age, it's also normal to experience changes in erectile function. Erections may take longer to develop, may not be as rigid or may require more direct stimulation to be achieved. Men may also notice that orgasms are less intense, the volume of ejaculate is reduced and recovery time increases between erections.

When erectile dysfunction proves to be a pattern or a persistent problem, however, it can interfere with a man's self-image as well as his sexual life. It may also be a sign of a physical or emotional problem that requires treatment.

Erectile dysfunction, formerly called impotence, was once a taboo subject. But attitudes are changing. More men are seeking help for the problem, and doctors are gaining a better understanding of what causes erectile dysfunction and are finding new and better ways to treat it.

Patterns of erectile dysfunction include:

• Occasional inability to obtain a full erection
• Inability to maintain an erection throughout intercourse
• Complete inability to achieve an erection

The penis contains two cylindrical, sponge-like structures that run along its length, parallel to the tube that carries semen and urine (urethra). When a man becomes sexually aroused, nerve impulses cause the blood flow to the cylinders to increase about seven times the normal amount. This sudden influx of blood expands the sponge-like structures and produces an erection by straightening and stiffening the penis. Continued sexual arousal or excitation maintains the higher rate of blood flow, keeping the erection firm. After ejaculation, or when the sexual excitation passes, the excess blood drains out of the spongy tissue, and the penis returns to its nonerect size and shape.

Specific steps take place to produce and sustain an erection:

• Arousal. The first step is sexual arousal, which men obtain from the senses of sight, touch, hearing and smell, and from thoughts.
• Nervous system response. The brain communicates the sexual excitation to the body's nervous system, which activates increased blood flow to the penis.
• Blood vessel response. A relaxing action occurs in the blood vessels that supply the penis, allowing more blood to flow into the shafts that produce the erection.

If something affects any of these factors or the delicate balance among them, erectile dysfunction can result.

Nonphysical causes may account for impotence. They may include:

• Psychological problems. The most common nonphysical causes are stress, anxiety and fatigue. Impotence is also an occasional side effect of psychological problems such as depression.
• Negative feelings. Feelings that you express toward your sexual partner — or that are expressed by your sexual partner — such as resentment, hostility or lack of interest also can be a factor in erectile dysfunction.

Still, the most frequent cause of erectile dysfunction isn't always psychological. Physical causes account for many cases of erectile dysfunction. These physical causes include:

• Nerve damage from longstanding diabetes (diabetic neuropathy)
• Cardiovascular disorders affecting the blood supply to the pelvis
• Certain prescription medications
• Operations for cancer of the prostate
• Fractures that injure the spinal cord
• Multiple sclerosis
• Hormonal disorders
• Alcoholism and other forms of drug abuse

In fact, erectile dysfunction may be one of the first signs of an underlying medical problem.

The physical and nonphysical causes of erectile dysfunction commonly interact. For instance, a minor physical problem that slows sexual response may cause anxiety about attaining an erection. Then the anxiety can worsen your erectile dysfunction.

A wide variety of physical and emotional risk factors can contribute to erectile dysfunction. They include:

• Physical diseases and disorders. Chronic diseases of the lungs, liver, kidneys, heart, nerves, arteries or veins can lead to impotence. So can endocrine system disorders, particularly diabetes. The accumulation of deposits (plaques) in your arteries (atherosclerosis) also can prevent adequate blood from entering the penis. And in some men, erectile dysfunction may be caused by low levels of the hormone testosterone (male hypogonadism).
• Surgery or trauma. Erectile dysfunction may result from an injury to the pelvic area or spinal cord. Surgery to treat bladder, rectal or prostate cancer also can result in erectile dysfunction. Prolonged bicycle riding can cause a temporary problem.
• Medications. A wide range of drugs — including antidepressants, antihistamines and medications to treat high blood pressure, pain and prostate cancer — can cause erectile dysfunction by interfering with nerve impulses or blood flow to the penis. Tranquilizers and sleeping aids also may pose a problem.
• Substance abuse. Chronic use of alcohol, marijuana or other drugs often causes erectile dysfunction and decreased sexual drive. Excessive tobacco use also can damage penile arteries.
• Stress, anxiety or depression. Psychological conditions also contribute to some cases of erectile dysfunction.

It's normal to experience erectile dysfunction on occasion. But if erectile dysfunction lasts longer than two months or is a recurring problem, see your doctor for a physical exam or for a referral to a doctor who specializes in erectile problems. Your own doctor or a specialist can help you determine the underlying cause or causes of erectile dysfunction and then help you find the right type of treatment.

Although you might view erectile dysfunction as a personal or embarrassing problem, it's important to seek treatment, especially if a physical cause might be to blame. In many cases, erectile dysfunction can be successfully treated. Also, see your doctor if the therapy or medication prescribed to treat erectile dysfunction isn't working for you. Don't try to combine medications or therapies on your own or deviate from prescribed doses.

Your doctor will want to ask questions about how or when your condition developed, the medications you take and any other physical conditions you may have. Your doctor will also want to discuss recent physical or emotional changes.

If your doctor suspects that physical causes are involved, he or she will likely want to take blood tests to check your level of male hormones and for other potential medical problems, such as diabetes. Your doctor may also want to try eliminating or replacing certain prescription drugs you're taking one at a time to see whether any are responsible for erectile dysfunction.

More specialized tests may include:

• Ultrasonography. This test can determine the adequacy of arterial circulation in your genital organs. Ultrasonography involves using a wand-like device (transducer) held over the blood vessels that supply the penis. The transducer emits sound waves that pass through body tissues and reflect back, producing an image to let your doctor see if your blood flow is impaired. The test often is done before and after injection of medication to see if there's an improvement in blood flow.
• Neurologic evaluation. Your doctor usually assesses possible nerve damage by conducting a physical examination to test for normal touch sensation in your genital area.
• Cavernosometry and cavernosography. Cavernosometry is a test that measures penile vascular pressure. Cavernosography involves injecting a dye into your blood vessels to permit your doctor to view any possible abnormalities in blood flow into and out of your penis.

If your doctor suspects that mainly nonphysical causes are to blame, he or she may ask whether you obtain erections during masturbation, with a partner or while you sleep. Most men experience many erections, without remembering them, during sleep. A simple test that involves wrapping a special perforated tape around your penis before going to sleep can confirm whether you have nocturnal erections. If the tape is separated in the morning, your penis was erect at some time during the night. Tests of this type confirm that there is not a physical abnormality causing erectile dysfunction, and that the cause is likely psychological.

A wide variety of options exist for treating erectile dysfunction. They include everything from medications and simple mechanical devices to surgery and psychological counseling. The cause and severity of your condition are important factors in determining the best treatment or combination of treatments for you. You and your doctor may also want to consider how much money you're willing to spend and the personal preferences of you and your partner. If erectile dysfunction is the result of a medical condition, the cost of treatment may be covered by insurance.

Oral medications
Three oral medications are available to treat ED. These include:

• Sildenafil (Viagra)
• Tadalafil (Cialis)
• Vardenafil (Levitra)

The Food and Drug Administration (FDA) approved Viagra in 1998, and it became the first oral medication for erectile dysfunction on the market. Since then, doctors have written millions of prescriptions for the blue, diamond-shaped tablets. But Viagra is no longer the only pill that treats this condition. Levitra and Cialis are two other options.

Viagra, Levitra and Cialis work in much the same way. Chemically known as phosphodiesterase inhibitors, these drugs enhance the effects of nitric oxide, a chemical messenger that relaxes smooth muscles in the penis. This increases the amount of blood and allows a natural sequence to occur — an erection in response to sexual stimulation. These medications don't automatically produce an erection. Instead they allow an erection to occur after physical and psychological stimulation. Many men experience improvement in erectile function after taking these medications regardless of the cause of their impotence.

These medications share many similarities, but they have differences as well. They vary in dosage, duration of effectiveness and possible side effects. Other distinctions — for example, which drug is best for certain types of men — aren't yet known. No study has directly compared these three medications.

Although these medications can help many people, not all men can or should take them to treat erectile dysfunction. If you've had a heart attack, stroke or life-threatening heart rhythm during the last six months, don't take these medications. If you've been told that sexual activity could trigger a cardiac event, discuss other options with your doctor. In addition, don't take Viagra, Levitra or Cialis with nitrate medications, such as the heart drug nitroglycerin. The combination of these medications, which work to widen (dilate) blood vessels, can cause dizziness, low blood pressure, and circulation and heart problems.

Don't expect these medications to fix your impotence immediately, because that's not always the case. Dosages may need adjusting. Or you may need to alter when you take the medication. Before taking any medication, make sure to discuss with your doctor its potential benefits and side effects.

Prostaglandin E (alprostadil)
Two treatments involve using a drug called alprostadil (al-PROS-tuh-dil). Alprostadil is a synthetic version of the hormone prostaglandin E. The hormone helps relax smooth muscle tissue in the penis, which enhances the blood flow needed for an erection. There are two ways to use alprostadil:

• Needle-injection therapy. With this method, you use a fine needle to inject alprostadil (Caverject, Edex) into the base or side of your penis. This generally produces an erection in five to 20 minutes that lasts about an hour. Because the injection goes directly into the spongy cylinders that fill with blood, alprostadil is an effective treatment for many men. And because the needle used is so fine, pain from the injection site is usually minor. Other side effects may include bleeding from the injection, prolonged erection and formation of fibrous tissue at the injection site. The cost per injection can be expensive. Injecting a mixture of alprostadil and other prescribed drugs may be a less expensive and more effective option. These other drugs may include papaverine and phentolamine (Regitine).
• Self-administered intraurethral therapy. This method's trade name is Medicated Urethral System for Erection (MUSE). It involves using a disposable applicator to insert a tiny suppository, about half the size of a grain of rice, into the tip of your penis. The suppository, placed about two inches into your urethra, is absorbed by erectile tissue in your penis, increasing the blood flow that causes an erection. Although needles aren't involved, you may still find this method painful or uncomfortable. Side effects may include pain, minor bleeding in the urethra, dizziness and formation of fibrous tissue.

Hormone replacement therapy
For the small number of men who have testosterone deficiency, testosterone replacement therapy may be an option.

Vacuum devices
This treatment involves the use of an external vacuum and one or more rubber bands (tension rings). To begin you place a hollow plastic tube, available by prescription, over your penis. You then use a hand pump to create a vacuum in the tube and pull blood into the penis. Once you achieve an adequate erection, you slip a tension ring around the base of your penis to maintain the erection. You then remove the vacuum device. The erection typically lasts long enough for a couple to have adequate sexual relations. You remove the tension ring after intercourse.

Vascular surgery
This treatment is usually reserved for men whose blood flow has been blocked by an injury to the penis or pelvic area. Surgery may also be used to correct erectile dysfunction caused by vascular blockages. The goal of this treatment is to correct a blockage of blood flow to the penis so that erections can occur naturally. But the long-term success of this surgery is unclear.

Penile implants
This treatment involves surgically placing a device into the two sides of the penis, allowing erection to occur as often and for as long as desired. These implants consist of either an inflatable device or semirigid rods made from silicone or polyurethane. This treatment is often expensive and is usually not recommended until other methods have been considered or tried first. As with any surgery, there is a small risk of complications such as infection.

Psychological counseling
If stress, anxiety or depression is the cause of your erectile dysfunction, your doctor may suggest that you, or you and your partner, visit a psychologist or psychiatrist with experience in treating sexual problems.

Although most men experience episodes of erectile dysfunction from time to time, you can take these steps to decrease the likelihood of occurrences:

• Limit or avoid the use of alcohol and other similar drugs.
• Stop smoking.
• Exercise regularly.
• Reduce stress.
• Get enough sleep.
• Deal with anxiety or depression.
• See your doctor for regular checkups and medical screening tests.

Whether the cause of erectile dysfunction is physical factors or psychological factors or a combination of both, it can become a source of mental and emotional stress for a man — and his partner. If you experience erectile dysfunction only on occasion, try not to assume that you have a permanent problem or to expect it to happen again during your next sexual encounter. Don't view one episode of erectile dysfunction as a lasting comment on your health, virility or masculinity.

In addition, if you experience occasional or persistent erectile dysfunction, remember your sexual partner. Your partner may see your inability to have an erection as a sign of diminished sexual desire. Your reassurance that this is not the case can be helpful in this situation.

To appropriately treat erectile dysfunction and strengthen your relationship with your partner, try to communicate openly and honestly about your condition. Couples may also want to seek counseling to confront any concerns they may have about erectile dysfunction and to learn how to discuss their feelings. Try to maintain this communication throughout the diagnosis and treatment process. In fact, treatment is often more successful if couples work together as a team.