What is Erectile Dysfunction (ED)?

Erectile dysfunction (ED) is a complex condition involving psychosocial and biological factors.  Erectile dysfunction is the inability to achieve or maintain an erect penis during sex. The typical patient reports these symptoms after a long period of normal erectile function. This type of erectile dysfunction is not caused by psychological or relationship issues or other hormone disorders.  ED is a common disorder of male sexual function, affecting all age groups with a considerable impact on quality of life.

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.

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.

Given the increasing trends in life expectancy across the Western world (i.e., the aging of the general population) and the high prevalence of diabetes and cardiovascular disease, the impact on lifestyle and quality of life imposed by ED in men is projected to be substantial.

Is erectile dysfunction associated with other illnesses?

Erectile dysfunction is associated with chronic illness. Drugs used to treat these illnesses may cause erectile dysfunction as a side effect.


What is the goal of treatment for erectile dysfunction?

The goal of treatment for erectile dysfunction is to restore erectile function.

What physically happens for an erection to occur?

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.

What causes erectile dysfunction (ED)?

Today, ED is considered a disorder with multiple causes. The current evidence suggests that about 80 percent of ED cases are of organic origin (i.e. a physical cause).Organic causes of ED may be vascular (e.g. cardiovascular disease, hypertension, lipid disorders, endothelial dysfunction), neurological (e.g. spinal cord injury, Parkinson’s disease, multiple sclerosis), iatrogenic (e.g. pelvic surgery,  prostatectomy, antipsychotic agents, antidepressants, beta-blockers, diuretics, antitestosterone hormonal agents), penile injury/anatomic abnormalities (e.g. Peyronie’s disease, priapism), tumors (e.g. prostate cancer, colorectal cancer), various conditions (chronic renal or hepatic failure, lower urinary tract symptoms, prostatic hyperplasia), substance use and abuse (e.g. alcohol, tobacco) or endocrine disorders (e.g. diabetes, andropause, hypogonadism, hyperprolactinemia, hypothyroidism). Some of the psychogenic causes of ED may be depression, dysphoria, or anxiety states.The majority of ED patients with organic causes present with vascular diseases and have decreased blood flow to the penis.In many patients the cause of ED may be a combination of psychological and organic factors.

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.

Lifestyle choices that contribute to heart disease and vascular problems also raise the risk of erectile dysfunction. Smoking, being overweight, and avoiding exercise are possible causes of 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.

How is ED diagnosed?

Patient History

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.

Physical Examination

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.

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 free testosterone in the blood can yield information about problems with the endocrine system and is indicated especially in patients with decreased sexual desire.

Other Tests

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.

Psychosocial Examination

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.

How is ED treated?

Oral phosphodiesterase type 5 (PDE–5) inhibitors are the first-line treatment options offered to patients with ED.  Patients receiving PDE–5 inhibitors experienced statistically significant and clinically relevant improvements in erectile functioning and satisfaction  compared with those receiving placebo.  The use of sildenafil was associated with statistically significant improvements in penile penetration and improved erection compared with placebo.

Today, unless contraindicated, the first-line therapies offered for the treatment of ED are lifestyle and risk factor modification (e.g. exercise and weight loss)and the use of the oral phosphodiesterase type 5 (PDE–5) inhibitors such as sildenafil, tadalafil, or vardenafil. Given that PDE–5 drugs may interact with nitrates with respect to vasodilatory effect, all PDE–5 drugs are contraindicated in patients taking nitrates for cardiac disease. The introduction, availability, and production of PDE–5 inhibitors have revolutionized the management of ED, allowing physicians to treat the condition in the primary care setting.

Although other types of medical treatments (e.g. intracavernosal injections, intraurethral suppositories) for erectile dysfunction have existed for years, their use has been associated with specific adverse events (e.g. local pain, priapism, fibrosis) and low compliance rates resulting from the invasive nature of these therapies. Topical therapies of agents that are approved by FDA for other indications have been explored as alternative options given their less invasive routes of administration (e.g. alprostadil, papaverine, organic nitrates). Other second-line treatment modalities for patients with refractory ED or who cannot tolerate PDE–5 therapy are hormonal treatments, vacuum constriction devices and surgical therapies (e.g. penile prosthesis implants, penile arterial bypass).Psychological counseling (e.g. psychotherapy) and recommended lifestyle modifications (e.g. smoking cessation, low-fat diet, physical activity, weight loss) should be offered to men with ED either alone or in combination with other treatments.

Most physicians suggest that treatments proceed from least to most invasive. For some men, making a few healthy lifestyle changes may solve the problem. Quitting smoking, losing excess weight, and increasing physical activity may help some men regain sexual function.

Cutting back on any drugs with harmful side effects is considered next. 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.

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. In March 1998, the Food and Drug Administration (FDA) approved 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 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 either Levitra or Cialis is 10 mg, and the physician may adjust this dose to 20 mg if 10 mg is insufficient. A lower dose of 5 mg is available for patients who take other medicines or have conditions that may decrease the body's ability to use the drug. Levitra is also available in a 2.5 mg dose.

None of these PDE inhibitors 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, tell your doctor if you take any drugs called alpha-blockers, which are used to treat prostate enlargement or high blood pressure. Your doctor may need to adjust your ED prescription. Taking a PDE inhibitor and an alpha-blocker at the same time (within 4 hours) can cause a sudden drop in 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.

Vacuum Devices

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:

to implant a device that can cause the penis to become erect to reconstruct arteries to increase flow of blood 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. 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. 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.

Measures of Efficacy in Erectile Dysfunction Therapy

From the patient’s perspective, the most important measures for defining successful ED treatment are: “cure, pleasure, partner satisfaction, reproduction, and naturalness.”To address the lack of well-defined standardized guidelines for the assessment of clinical outcomes in comparative trials of ED therapies, an International Consensus Advisory Panel was convened in 2002 in Montréal, Canada, where a new conceptual framework for treatment effectiveness was adopted.


According to this framework, treatment effectiveness consists of two dimensions: treatment response and treatment satisfaction. Treatment response, in turn, consists of an integrated assessment of efficacy (i.e., ability of an agent to promote achievement and maintenance of adequate erection) and tolerability (i.e., side effects). The response was categorized as complete responder (e.g. consistent achievement and maintenance of full erection and ability to tolerate side effects), partial responder (e.g. ability to achieve full erection but not on a consistent basis over time and/or patients who experienced adequate efficacy but also had bothersome side effects of treatment), or nonresponder (e.g. patients who failed to respond in a clinically significant manner to the treatment and/or those who experienced intolerable effects at any dosage). Generally, the treatment efficacy in ED trials is assessed using event-log or diary-based questionnaires such as the IIEF and IIEF–5, the sexual encounter profile (SEP), and global assessment questions (GAQs).These measures are all based on patient responses and therefore are subjective in nature.The other domain of treatment effectiveness—treatment satisfaction— is defined as the degree to which the effects of any particular treatment correspond or exceed the expectations of a patient and his partner.This domain was categorized as complete satisfaction (e.g. both the patient and his partner were satisfied), partial satisfaction (e.g. either the patient or the partner was not satisfied), and no satisfaction (neither the patient nor the partner was satisfied). In summary, according to this framework, the overall measure of treatment effectiveness should ideally integrate the information on both treatment response (i.e., efficacy and tolerability) and treatment satisfaction (i.e., self-rated degree of patient-partner satisfaction).


Please Note: ED Drugs Are Not Safe for Everyone

Many men now take a pill to treat erection problems. Current brands include Viagra, Levitra, and Cialis. These drugs work by affecting blood pressure. They are not safe for everyone. Never take Viagra, Levitra, or Cialis if you take heart medicines called nitrates. Doing so could cause a sudden — and dangerous — drop in blood pressure. Also, tell your doctor if you take any drugs called alpha-blockers, which are used to treat prostate enlargement or high blood pressure. Before taking drugs to treat ED, talk to your doctor about the benefits and risks so you can make an informed choice.

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