Erectile dysfunction (ED), formerly called impotence, can affect men of all ages, although it is much more common among older men. It is normal for men to occasionally experience ED. However, if the problem becomes chronic, it can have adverse effects on relationships, emotional health, and self-esteem.
ED can be a symptom of an underlying health condition. If ED becomes an on-going problem, it is important to talk to your doctor.
Phosphodiesterase-5 (PDE5) Inhibitors
ED is usually treated with a PDE5 inhibitor drug such as:
These drugs are generally safe and effective for most men. They may not be appropriate for men with certain health conditions, such as severe heart disease, heart failure, uncontrolled high blood pressure, diabetes, or a history of stroke or heart attack. Men who take nitrate drugs cannot use PDE5 inhibitors. PDE5 inhibitors can also interact with other medications. Talk to your doctor about whether PDE5 inhibitor drugs are a safe choice for you.
Other treatments for ED include:
It is very important to treat any underlying health conditions that may be causing ED. It is also important to engage in healthy lifestyle behaviors by eating right, staying physically active, reducing stress, and stopping smoking and substance abuse.
The FDA has issued a warning that testosterone products may increase the risk for heart attack, stroke, and death from cardiovascular causes. The FDA has also required that all testosterone products' labels include information on increased risk for blood clots in the veins. These products can have other serious health risks as well.
Testosterone products are approved to treat men who have hypogonadism (low testosterone levels). ED can be one of the symptoms of low testosterone. However, it is not clear if these products are helpful for ED in men who have hypogonadism. They should not be prescribed to men who have normal testosterone levels. Doctors are concerned that these products are being overprescribed due to increased advertising, and not medical need.
Erectile dysfunction (formerly called impotence) is the inability to achieve or maintain an erection that is sufficiently rigid for sexual intercourse. Sexual drive and the ability to have an orgasm are not necessarily affected. Because all men have erection problems from time to time, doctors diagnose erectile dysfunction if a man fails to maintain an erection satisfactory for intercourse on at least 25% of attempts. Worldwide, erectile dysfunction occurs in close to 20% of men.
Erectile dysfunction (ED) is not new in either medicine or human experience, but it is often not easily or openly discussed. Cultural expectations of male sexuality inhibit many men from seeking help for a disorder that can usually benefit from treatment.
The Structure of the Penis
The penis is composed of the following structures:
These structures are made up of erectile tissue. Erectile tissue is rich in tiny pools of blood vessels called cavernous sinuses. Each of these vessels are surrounded by smooth muscles and supported by elastic tissue composed of a protein called elastin.
Erectile Function and Nitric Oxide (NO)
The penis is either flaccid or erect depending on the state of arousal. In the flaccid, or unerect penis, the following normally occurs:
During arousal the following occurs:
A proper balance of certain chemicals, gases, and other substances is critical for erectile health.
The protein collagen is the major component in structural tissue in the body, including in the penis. However, excessive amounts of collagen can form scar tissue, which can impair erectile function.
Oxygen-rich blood is one of the most important components for erectile health. Oxygen levels vary widely from very low levels in the flaccid state to very high levels in the erect state. During sleep, a man can normally have 3 to 5 erections per night, bringing oxygen-rich blood to the penis. The primary cause of oxygen deprivation is ischemia, or the blockage of blood vessels. Blood flow-reducing conditions that lead to heart disease, such as atherosclerosis, may also contribute to ED.
Calcium is an essential ion for the normal contraction and relaxation of smooth muscle tissues which regulate blood flow in the corpus cavernosum.
Testosterone and Other Hormones
Normal levels of hormones, especially testosterone, are essential for libido (sex drive) and erectile function, although their exact role is not clear.
Over the past decades, the medical perspective on the causes of erectile dysfunction (ED) has shifted. Doctors used to think that almost all cases of ED were related to psychological factors. Now doctors believe that up to 85% of ED cases are caused by medical or physical problems. Only 15% are completely psychologically based. Sometimes, ED is due to a combination of physical and psychological causes.
In general, psychologically based ED is more likely to develop suddenly with complete, immediate loss of function. This problem may be present most of the time or only in certain situations. These men will often still have erections upon awakening.
ED from organic or medical causes occurs gradually over time and progressively becomes worse. ED is present with most or all sexual interactions and these men either lack an erection upon awakening, or have poor erections.
A number of medical conditions share a common problem with ED, such as the impaired ability of blood vessels to open and allow normal blood flow.
Heart disease, atherosclerosis, high blood pressure, and high cholesterol levels are major risk factors for ED. Peripheral artery disease (PAD), a form of atherosclerosis, is very common in men who have ED. In fact, erectile problems may be a warning sign of these conditions in men at risk for atherosclerosis. Men who experience ED due to vascular causes have a greater risk for angina, (chest pain due to low oxygen levels in the blood), heart attack, and stroke.
ED is also a very common problem in men with high blood pressure. Many of the drugs used to treat hypertension (diuretics, calcium channel blockers, and beta-blockers) may also cause ED.
Diabetes is a major risk factor for ED. Damage to blood vessels and nerves is a common complication of diabetes. When the blood vessels or nerves of the penis are involved, ED can result. Diabetes is also associated with heart disease and chronic kidney disease, which are other risk factors for ED.
Obesity increases the risk for diabetes, heart disease, and ED.
Metabolic syndrome is a risk factor for ED in men older than age 50 years. It is a cluster of conditions that includes obesity and abdominal fat, unhealthy cholesterol and triglyceride levels, high blood pressure, and insulin resistance.
There appears to be a relationship between ED and the lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH or "enlarged prostate"). Men who have one condition often have the other. Both conditions share common risk factors including older age, high blood pressure, and diabetes. In addition, surgical and drug treatments for BPH can increase the risk for ED.
Diseases, such as Parkinson disease, multiple sclerosis, and stroke, can cause ED.
Endocrinologic conditions include diseases or conditions that involve abnormalities of the glands and hormonal imbalance. Hypogonadism, known informally as "low T," is a medical condition that results from low levels of the male hormone testosterone (androgen deficiency). Symptoms of hypogonadism can include reduced sexual desire (low libido) and ED.
However, low testosterone as the sole cause of ED, likely affects only a small percentage of men. Hypogonadism is also associated with very small or shrinking testicles, loss of muscle mass, increased body fat, reduced bone density, fatigue, anemia, and declining sperm production. Many men with hypogonadism are infertile.
Hypogonadism is classified as either primary or secondary. Primary hypogonadism is caused by diseases or defects in the testicles that affect the production of testosterone. Secondary hypogonadism is due to problems in the hypothalamus or pituitary gland that cause high levels of the hormone prolactin. Hypothalamus and pituitary abnormalities also cause low levels of other hormones such as follicle-stimulating hormone and luteinizing hormone. These hormonal imbalances can result in low libido and ED.
Other hormonal and endocrinologic causes of ED include thyroid and adrenal gland problems.
Spinal cord injury and pelvic trauma, such as a pelvic fracture, can cause nerve damage that result in ED. Other conditions that can injure the spine and cause ED include spinal cord tumors, spina bifida, and a history of polio.
Certain types of surgery and radiation treatments can increase the risk for erectile dysfunction:
Note: Vasectomy does NOT cause ED.
ED can be a side effect of certain medications. They include:
Anxiety has both emotional and physical consequences that can affect erectile function. It is among the most frequently cited contributors to psychological ED.
Even simple stress can affect sexual function.
Depression can reduce sexual desire and is associated with ED.
Troubles in relationships often have a direct impact on sexual function.
For most men, ED is primarily associated with older age. However, ED is not inevitable with age. Severe ED often has more to do with age-related disease than age itself. In particular, older men are more likely to have heart disease, diabetes, and high blood pressure than younger men. Such conditions and some of their treatments are causes of ED.
Smoking contributes to the development of ED, mainly because it increases the effects of other blood vessel disorders, including high blood pressure and atherosclerosis. Smokers have an increased risk for ED compared with non-smokers. ED is more likely in those who smoke for longer periods of time or who are heavier smokers. In turn, quitting smoking can reduce this risk.
Heavy drinking can cause ED. Alcohol depresses the central nervous system and impairs sexual function.
Heroin, cocaine, methamphetamines, and marijuana can affect sexual function. Opioid use is associated with the development of erectile dysfunction.
Weight and Sedentary Lifestyle
Obesity is a risk factor for ED. Lack of exercise and a sedentary lifestyle can lead to obesity and other health problems associated with ED.
Your doctor will ask about various physical and psychological factors that may be causing ED. The doctor will also perform a physical exam.
The doctor will ask about:
In addition, the doctor will ask about your sexual history, which may include:
If appropriate, the doctor may also interview your sexual partner.
The doctor will perform a physical exam, including examination of the genitals and a digital rectal examination (the doctor inserts a gloved and lubricated finger into the person's rectum) to check for prostate abnormalities. The doctor will also examine your breasts and thyroid gland. The doctor should check your blood pressure and evaluate your blood circulation by checking the pulses in your legs.
Because ED and atherosclerosis are often linked, it is important to check cholesterol levels. Similarly, the doctor may order tests for blood sugar (glucose) levels to check if diabetes is a factor. A blood test to measure total serum testosterone is usually done. This test should be drawn in the morning.
If your test indicates low testosterone, the doctor should retest a second time to confirm the results. Other tests that measure hormone level involved in the brain and body's production of testosterone may be needed if testosterone levels are low. A diagnosis of hypogonadism requires clinical signs and symptoms associated with the condition in addition to low testosterone levels in the blood.
The doctor may also test for thyroid and adrenal gland dysfunction. For more sophisticated tests, the doctor may refer you to specialist such as an urologist or endocrinologist.
A number of tests are available that can help identify the cause. However, unless the presenting symptoms and findings are unusual or complex, this type of testing is not required or useful for most people. Some tests with more supportive evidence behind them include:
Many physical and psychological situations can cause ED, and brief periods of ED are normal. Every man experiences ED from time to time. Nevertheless, if the problem persists, men should seek professional help, particularly since ED is usually treatable and may also be a symptom of an underlying health problem. It is important to treat any medical condition that may be causing ED.
Overall treatment approach includes:
Before treatment, men with ED should be assessed for their risk for cardiovascular disease. Men found to be at high risk include those with angina, recent history of heart attack, certain abnormal heart rhythms, and poorly controlled high blood pressure. These men should be evaluated and treated first before a trial of therapy for ED. Any risk factors for heart disease should be addressed in all men.
Drug therapy with PDE5 inhibitors is the main treatment for ED. Sildenafil (Viagra), vardenafil (Levitra, Staxyn), tadalafil (Cialis), and avanafil (Stendra) are the PDE5 inhibitor drugs approved for treating ED. In general, if a man is a candidate for PDE5 inhibitor therapy and is satisfied with the results, no further treatment is necessary.
PDE5 inhibitors are not safe or effective for all men. Men who cannot or choose not to take the drugs may have other options, including:
Ultimately, how successful the medical treatment is and how well it is accepted depends, in large part, on the man's expectations and how he and his partner both adapt to the procedure.
Some form of psychological, behavioral, or sexual therapy may be recommended for certain men.
No matter what the treatment, a healthy lifestyle is important for restoring and maintaining erectile function. This includes a heart-healthy diet, regular exercise, and engaging in activities that help reduce stress.
PDE5 inhibitor drugs are generally the first choice of treatment for ED. They are:
All of these drugs are known as phosphodiesterase-5 (PDE5) inhibitors and are approved for treatment of ED. By blocking the PDE-5 enzyme, these drugs stop degradation of the cyclic GMP molecule, which keeps the smooth muscle relaxed, helping arteries widen and increase blood flow and improving erection.
PDE5 inhibitor drugs come in pill form and are taken by mouth. Vardenafil is available as a standard pill (Levitra) or as a quickly dissolving tablet (Staxyn).
These medicines augment an erection but do not actually induce the erectile response.
These drugs all work equally well. A doctor usually selects one of the brands based on the person's individual preference, ease of use, and cost of medication.
PDE5 inhibitors are a good choice for men of any age who are in good health and who do not have conditions that prevent taking them.
However, PDE5 inhibitors are not suitable for everyone. Men who take nitrate drugs for angina cannot take PDE5 inhibitors. The PDE5 inhibitors are less effective in men with diabetes and in men who have been treated for prostate cancer. Men who take certain alpha-blockers for high blood pressure or benign prostatic hyperplasia (BPH) should take PDE5 inhibitors with extra care if at all. Tadalafil (Cialis) is approved to treat symptoms of enlarged prostate in men who have both BPH and erectile dysfunction.
Men with the following conditions should not take PDE5 inhibitors:
PDE5 inhibitors work only when the man experiences some sexual arousal. The pill should be taken about 1 hour before sexual intercourse. It generally starts to work within 10 to 30 minutes. The availability of these drugs may last for several hours in the blood stream, and tadalafil may last for up to 36 hours. The erection should not last for more than 4 hours. If it does, it becomes an emergency and men should seek medical attention.
Do not take more than one pill a day. Sildenafil should be taken on an empty stomach. Vardenafil, tadalafil, and avanafil may be taken with or without food.
Success rates increase with the number of attempts, so don't be discouraged if the drug does not work at first.
PDE5 inhibitors are also sometimes used in combination with testosterone replacement therapy for men with hypogonadism (low testosterone levels). Some research indicates that the addition of testosterone provides little benefit.
As described above, these drugs are primarily used to induce an erection. Some have proposed taking these drugs in a regularly scheduled manner after prostate surgery in the hope of helping recovery of erectile function. However, this method has not been proven in randomized controlled trials.
Common side effects of PDE inhibitors include flushing, upset stomach, headache, nasal congestion, back pain, and dizziness.
Effects on the Heart
There have been reports of fatal heart attacks in a small percentage of men taking PDE5 inhibitors. These medications can cause sudden and dangerous drops in blood pressure when the drug is taken with nitrate drugs, which are used for angina. Common nitrate drugs include nitroglycerine, isosorbide mononitrate, isosorbide dinitrate, erythrityl tetranitrate, pentaerythritol tetranitrate, and sodium nitroprusside. Men who use nitrates, including related substances such as amyl nitrate ("poppers"), should never take sildenafil, vardenafil, tadalafil, or avanafil.
Sexual intercourse itself involves an increase in physical exertion and a very small risk for heart attack for people with heart disease or heart disease risk factors. If you have heart disease or have recently had a heart attack, talk with your doctor about whether you can safely have sex.
In rare cases, men who take these drugs develop vision problems that include seeing a blue haze, temporary increased brightness, and even temporary vision loss in a few cases. The effect is usually temporary, lasting a few minutes to several hours. Men at risk for eye problems who take PDE5 inhibitors should have regular eye examinations with an ophthalmologist. Men should also see an eye doctor if visual problems last more than a few hours.
In a few cases, these drugs have been associated with partial vision loss. The vision loss is caused by non-arteritic anterior ischemic optic neuropathy (NAION), a condition that occurs from poor blood flow to optic nerves. However, ED is itself linked to the same vascular problems that cause NAION. Men who have diabetes, high blood pressure, and heart disease are at higher risk for ED as well as other vascular problems such as NAION. Although the risk of blindness appears small, men who experience a sudden loss of vision should immediately stop taking the drug and contact their doctor.
A small number of men have experienced sudden hearing loss in one ear, sometimes accompanied by ringing in the ears and dizziness. If you have this symptom, immediately contact your doctor.
Priapism is sustained, painful, and unwanted erection that lasts for longer than 4 hours. PDE5 inhibitors pose a very low risk for priapism in most men with the exception of young men with normal erectile function. Priapism is an emergency situation that requires prompt treatment to prevent permanent damage to the penis.
In addition to serious interactions with nitrates, PDE5 inhibitors may also interact with certain antibiotics, such as erythromycin, and acid blockers, such as cimetidine (Tagamet, generic). Inform your doctor about all medications you take.
Some preliminary research suggested that men who take sildenafil may be at increased risk for developing skin cancer (melanoma). A more recent review of data does not support sildenafil as a cause for melanoma. Men who have had melanoma or are at risk for it should discuss this issue with their doctors.
Alprostadil is derived from a natural substance, prostaglandin E1, which opens blood vessels. This medicine is an effective treatment for many men with ED. It can be administered by:
Alprostadil is not an appropriate choice for men with:
Injected alprostadil (Caverject, Edex) is delivered through a very small needle that the man inserts into the erectile tissue of his penis. Although this treatment is very effective, some men find the injections to be painful or uncomfortable.
The drug should not be injected more than 3 times a week and no more than once within 24-hour period.
The MUSE system delivers alprostadil with a device inserted through the urethra using suppository pellets. The device is a thin applicator tube with a button at the top. It works in the following way:
The MUSE system should not be used more than twice a day and is not appropriate for men with abnormal penis anatomy.
Side Effects of Most Alprostadil Methods
Certain side effects are common to all methods of alprostadil administration, although they may differ in severity depending on how the drug is given:
Your doctor may prescribe another injectable option made up of a combination of 3 or 4 other medications including papaverine, phentolamine mesylate, prostaglandin E1, and atropine sulfate. Side effects and precautions are similar to those of alprostadil. This treatment is usually ordered through a compounding pharmacy.
Studies have been inconclusive as to whether testosterone replacement therapy is helpful for men with ED. Men with hypogonadism (low testosterone levels and impaired sperm production or function) may benefit, but men who have ED and normal testosterone levels are not likely to benefit from testosterone therapy. Before considering testosterone therapy, men should be sure that their hormone levels have been measured correctly and accurately and found to be low on at least two separate occasions.
Men should be wary of advertising that pushes testosterone replacement therapy for "low T," an informal term for low testosterone that many doctors regard with skepticism. Testosterone levels decrease with aging and there is no scientific consensus on what testosterone levels constitute "low T". Furthermore, male hypogonadism is a condition that involves more than simply low testosterone levels.
There is also no definitive evidence that testosterone treatment helps improve symptoms such as sexual function in men who have low testosterone levels. While the benefits of testosterone treatment are unclear, there is proven evidence of potential health risks. If you are considering testosterone replacement therapy, be sure to discuss with your doctor all of its possible risks and benefits.
Forms of testosterone therapy include:
Side effects may include acne, breast enlargement or soreness, high blood pressure, and mood swings Testosterone therapy can also increase cholesterol levels, prostate specific antigen (PSA) levels, red blood cell count. If you take testosterone therapy, your doctor should monitor your cholesterol, PSA, and hematocrit (red blood cell) levels, and liver function.
Serum testosterone levels should be followed during treatment. An initial 3 months trial is most often recommended. Prostate specific antigen testing or PSA (for prostate cancer) must be done before treatment and periodically after that. Liver functions test and lipid profiles should also be monitored.
Testosterone therapy may increase the risk for the following serious side effects:
Vacuum erection devices, also called vacuum constriction devices, are another option for men with ED. They are available without prescription and have a high success rate, but are cumbersome and may be difficult to use for some men. They typically work as follows:
Lack of spontaneity is the major drawback to this method. There are few side effects.
Penile implants are an option for men who cannot take medication or have not been helped by less invasive treatments. In general, implants work well in restoring sexual function, and men are usually satisfied with the results.
Two types of surgical implants are used for the treatment of ED:
Erectile tissue is permanently damaged when these devices are implanted, and these procedures are irreversible. Although uncommon, mechanical breakdown can occur, or the device can slip or bulge. In addition, a less than optimal quality of erection may result. Infection is a rare, but serious, complication.
In rare cases, penile vascular surgery may be considered as treatment for ED. Two types of operations are most commonly performed:
These surgeries may be tried where there is clear evidence of narrowing of the blood supply to the penis. The ideal candidates who are felt most likely to benefit from this type of surgery are younger men with no cardiovascular disease and isolated narrowing of an artery supplying the penis usually caused by pelvic trauma.
According to the American Urological Association, men who smoke or who have the following conditions are not candidates for penile vascular surgeries:
The revascularization procedure usually involves taking an artery from a leg and then surgically connecting it to the arteries at the back of the penis, bypassing the blockages and restoring blood flow. Penile arterial revascularization is mainly used for young men (under age 45) who have blood vessel injury caused by events such as blunt trauma or pelvic fracture.
Venous ligation is performed when the penis is unable to store a sufficient amount of blood to maintain an erection. This operation ties off or removes veins that are causing an excessive amount of blood to drain from the erection chambers. Long-term success rates for this procedure are less than 50 percent.
Doctors are investigating the use of drug-coated stents (similar to those used in angioplasty for heart blockages) for treating ED in men who have not been helped by drug therapy. The stents are tiny, expandable metal mesh tubes that are implanted in an artery that provides blood flow to the penis. Only men with specific types of blood flow blockages caused by atherosclerosis are candidates for this procedure. These stents are currently only being studied in clinical trials. They have not yet been approved for ED treatment.
Low Intensity Extracorporeal Shock Wave Treatment (LI-ESWT)
A recent non-invasive treatment method using shock waves is under investigation as a novel ED therapy. This method is based on the idea that a type of acoustic waves focused on an organ can release molecules and help blood supply of that organ function better. Studies using LI-ESWT for ED had mixed results, and more research is needed.
Because many cases of ED are due to reduced blood flow from blocked arteries, it is important to maintain the same healthy lifestyle habits used to prevent heart disease.
Eat a heart-healthy diet rich in fresh fruits and vegetables, whole grains, and fiber and low in saturated fats and sodium. Because ED is generally related to circulation problems, diets that benefit the heart are especially important.
Foods that some people claim to have qualities that enhance sexual drive include chilies, chocolate, scallops, oysters, olives, and anchovies. No evidence exists for these claims.
Being overweight can contribute to ED. Try to achieve and maintain a healthy weight.
Regular exercise is helpful for weight control, stress reduction, and a healthy heart.
Alcohol and Smoking
If you drink alcohol, do so in moderation. Alcohol abuse can contribute to ED. Smoking is clearly correlated with ED. Quitting smoking is essential.
Staying sexually active may help prevent ED. Frequent erections stimulate blood flow to the penis.
If medications are causing ED, discuss with your doctor whether to change to a different medication or reduce the dosage.
Even if ED is caused by a physical problem, interpersonal, supportive, or behavioral therapy are often helpful for men and their partners.
Manufacturers of herbal remedies and dietary supplements do not need FDA approval to sell their products. Such products can be sold without any proof of efficacy or safety. Just like a drug, herbs and supplements can affect the body's chemistry, and therefore have the potential to produce harmful side effects. There have been a number of reported cases of serious and even lethal side effects from these products. You should always check with your doctor before using any herbal remedies or dietary supplements.
There is no evidence that any herbal product, vitamin, or dietary supplement can improve erections or sexual performance in men or women. Despite this, many herbs and dietary supplements are marketed as aphrodisiacs. Aphrodisiacs are substances that are claimed to increase sexual drive, performance, or desire. Recently, the FDA has warned that several products being sold over the counter as aphrodisiac supplements actually contain hidden ingredients, such as varying amounts of prescription PDE-5 inhibitors, and are not safe for use. There are several specific concerns for people taking alternative remedies for ED.
Yohimbe is derived from the bark of a West African tree. Side effects include nausea, insomnia, nervousness, and dizziness. Large doses of yohimbe can increase blood pressure and heart rate and may cause kidney failure. However, yohimbe has not been shown to be any better than placebo for enabling sexual intercourse.
Viramax is a commercial product that contains yohimbine, the active chemical ingredient of yohimbe, and three other herbs: catuaba, muira puama, and maca. It has not been proven to be either effective or safe, and interactions with medications are unknown.
GBL is found in products marketed for improving sexual function (Verve and Jolt). This substance can convert to a chemical that can cause toxic and life-threatening effects, including seizures and even coma.
Although the risks for gingko biloba appear to be low, there is an increased risk for bleeding at high doses and interaction with vitamin E, anti-clotting medications, and aspirin and other NSAIDs. Large doses can cause convulsions. Commercial gingko preparations have also been reported to contain colchicine, a substance that can be harmful in people with kidney or liver problems.
L-arginine (also called arginine)
Arginine may cause gastrointestinal problems. It can also lower blood pressure and change levels of certain chemicals and electrolytes in the body. It may increase the risk for bleeding. Some people have an allergic reaction to it, which in some cases may be severe. It may worsen asthma.
DHEA is a precursor hormone to male and female sex hormones. DHEA from soy or yam is sold as a supplement. Studies show inconclusive results in its treatment for ED. DHEA may interact dangerously with other medications.
Spanish fly, or cantharides, which is made from dried beetles, is the most widely-touted aphrodisiac but can be particularly harmful. It irritates the urinary and genital tract and can cause infection, scarring, and burning of the mouth and throat. In some cases, it can be life threatening. No one should try any aphrodisiac without consulting a doctor.
Other Dietary Supplements Marketed for ED
There are numerous products marketed as "all-natural" dietary supplements and promoted as treatments for ED and sexual enhancement. The FDA has not approved any of these products. In recent years, the FDA has banned many of these dietary supplements and warns that they contain the same or similar chemical ingredients used in PDE5 inhibitor prescription drugs.
Basaria S, Harman SM, Travison TG, et al. Effects of testosterone administration for 3 years on subclinical atherosclerosis progression in older men with low or low-normal testosterone levels: a randomized clinical trial. JAMA. 2015;314(6):570-581. PMID: 26262795 www.ncbi.nlm.nih.gov/pubmed/26262795.
Berookhim BM, Mulhall JP. Erectile dysfunction. In: Cronenwett JL, Johnston W, eds. Rutherford's Vascular Surgery. 8th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 82.
Bhasin S, Cunningham GR, Hayes FJ, et al. Testosterone therapy in men with androgen deficiency syndromes: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2010;95(6):2536-2559. PMID: 20525905 www.ncbi.nlm.nih.gov/pubmed/20525905.
Burnett AL. Evaluation and management of erectile dysfunction. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:chap 27.
Gianatti EJ, Dupuis P, Hoermann R, Zajac JD, Grossman M. Effect of testosterone treatment on constitutional and sexual symptoms in men with type 2 diabetes in a randomized, placebo-controlled clinical trial. J Clin Endocrinol Metab. 2014;99(10):3821-3828. PMID: 24978674 www.ncbi.nlm.nih.gov/pubmed/24978674.
Li WQ, Qureshi AA, Robinson KC, Han J. Sildenafil use and increased risk of incident melanoma in US men: a prospective cohort study. JAMA Intern Med. 2014;174(6):964-970. PMID: 24710960 www.ncbi.nlm.nih.gov/pubmed/24710960.
Loeb S, Ventimiglia E, Salonia A, Folkvaljon Y, Stattin P. Meta-analysis of the association between phosphodiesterase inhibitors (PDE5Is) and risk of melanoma. J Natl Cancer Inst. 2017;109(8). PMID: 29117385 www.ncbi.nlm.nih.gov/pubmed/29117385.
Lu Z, Lin G, Reed-Maldonado A, Wang C, Lee YC, Lue TF. Low-intensity extracorporeal shock wave treatment improves erectile function: a systematic review and meta-analysis. Eur Urol. 2017;71(2):223-233. PMID: 27321373 www.ncbi.nlm.nih.gov/pubmed/27321373.
Lue TF. Physiology of penile erection and pathophysiology of erectile dysfunction. In: Wein AJ, Kavoussi LR, Partin AW, Peters CA, eds. Campbell-Walsh Urology. 11th ed. Philadelphia, PA: Elsevier; 2016:chap 26.
Miner M, Nehra A, Jackson G, et al. All men with vasculogenic erectile dysfunction require a cardiovascular workup. Am J Med. 2014;127(3):174-182. PMID: 24423973 www.ncbi.nlm.nih.gov/pubmed/24423973.
Paduch DA, Brannigan RE, Fuchs EF, Kim ED, Marmar JL, Sandlow JI. The laboratory diagnosis of testosterone deficiency. Urology. 2014;83(5):980-988. PMID: 24548716 www.ncbi.nlm.nih.gov/pubmed/24548716.
Pisansky TM, Pugh SL, Greenberg RE, et al. Tadalafil for prevention of erectile dysfunction after radiotherapy for prostate cancer: the Radiation Therapy Oncology Group  randomized clinical trial. JAMA. 2014;311(13):1300-1307. PMID: 24691606 www.ncbi.nlm.nih.gov/pubmed/24691606.
Prabhu V, Alukal JP, Laze J, Makarov DV, Lepor H. Long-term satisfaction and predictors of use of intracorporeal injections for post-prostatectomy erectile dysfunction. J Urol. 2013;189(1):238-242. PMID: 23174252 www.ncbi.nlm.nih.gov/pubmed/23174252.
Rew KT, Heidelbaugh JJ. Erectile dysfunction. Am Fam Physician. 2016;94(10):820-827. PMID: 27929275 www.ncbi.nlm.nih.gov/pubmed/27929275.
Rogers JH, Goldstein I, Kandzari DE, et al. Zotarolimus-eluting peripheral stents for the treatment of erectile dysfunction in subjects with suboptimal response to phosphodiesterase-5 inhibitors. J Am Coll Cardiol. 2012;60(25):2618-2627. PMID: 23177300 www.ncbi.nlm.nih.gov/pubmed/23177300.
Shamloul R, Ghanem H. Erectile dysfunction. Lancet. 2013;381(9861):153-165. PMID: 23040455 www.ncbi.nlm.nih.gov/pubmed/23040455.
Skeldon SC, Cheng L, Morgan SG, Detsky AS, Goldenberg SL, Law MR. Erectile dysfunction medications and treatment for cardiometabolic risk factors: a pharmacoepidemiologic study. J Sex Med. 2017;14(12):1597-1605. PMID: 29198514 www.ncbi.nlm.nih.gov/pubmed/29198514.
Vigen R, O'Donnell CI, Barón AE, et al. Association of testosterone therapy with mortality, myocardial infarction, and stroke in men with low testosterone levels. JAMA. 2013;310(17):1829-1836. PMID: 24193080 www.ncbi.nlm.nih.gov/pubmed/24193080.
Zhao S, Deng T, Luo L, et al. Association between opioid use and risk of erectile dysfunction: a systematic review and meta-analysis. J Sex Med. 2017;14(10):1209-1219. PMID: 28923307 www.ncbi.nlm.nih.gov/pubmed/28923307.
Reviewed By: Jennifer Sobol, DO, urologist with the Michigan Institute of Urology, West Bloomfield, MI. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.