The recommended starting dose of tadalafil for use as needed for most patients is 10 mg taken orally approximately one hour before sexual activity. A doctor may adjust the dose higher to 20 mg or lower to 5 mg depending on efficacy and side effects. Doctors recommended that patients take tadalafil no more frequently than once per day. Some patients can take tadalafil less frequently since the improvement in erectile function may last 36 hours. Patients may take tadalafil with or without food. Tadalafil is currently the only PDE5 inhibitor that is FDA-approved for daily use for erectile dysfunction and is available in 2.5 mg or 5 mg dosages for daily use.

Erectile dysfunction (ED) is commonly called impotence. It’s a condition in which a man can’t achieve or maintain an erection during sexual performance. Symptoms may also include reduced sexual desire or libido. Your doctor is likely to diagnose you with ED if the condition lasts for more than a few weeks or months. ED affects as many as 30 million men in the United States.


ED usually has something physical behind it, particularly in older men. But psychological factors can be a factor in many cases of ED. Experts say stress, depression, poor self-esteem, and performance anxiety can short-circuit the process that leads to an erection. These factors can also make the problem worse in men whose ED stems from something physical.
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional medical advice, diagnosis or treatment and should not be relied on to make decisions about your health. Never ignore professional medical advice in seeking treatment because of something you have read on the WebMD Site. If you think you may have a medical emergency, immediately call your doctor or dial 911.

One of the first steps is to distinguish between physiological and psychological ED. Determining whether involuntary erections are present is important in eliminating the possibility of psychogenic causes for ED.[2] Obtaining full erections occasionally, such as nocturnal penile tumescence when asleep (that is, when the mind and psychological issues, if any, are less present), tends to suggest that the physical structures are functionally working.[19][20] Similarly, performance with manual stimulation, as well as any performance anxiety or acute situational ED, may indicate a psychogenic component to ED.[2]
Since sexual arousal is a complex process involving hormones, emotions, nerves, muscles, blood vessels and the brain, a malfunction in any of these can lead to ED. Stress, exhaustion and psychological issues can also contribute, and anxiety over maintaining an erection can actually make it harder to attain. In short, any condition that inhibits blood flow to the penis can lead to ED.

The vacuum device creates a vacuum to pull blood into the penis. Unlike a normal erection, the inflow of blood does not continue once the individual removes the vacuum device. The rubber band placed at the base of the penis constricts the penis to prevent the blood from leaving the penis. As there is no inflow or outflow of blood when the rubber band is in place, it is uncommon for the tip of the penis (the glans) to appear a little blue and the penis to be cooler. Once intercourse is completed, the individual removes the rubber band and the blood drains out of the penis.


Because impotence can be due to health problems that can affect the whole body, and because it can interfere with one’s quality of life, it is important to talk with your doctor if you have trouble attaining or maintaining an erection. With increasing discussion of impotence in the media, coupled with advances in treatment, men are now much more comfortable talking with their doctors about impotence. It is currently estimated that between 15 and 30 million men in the United States are affected by impotence (Source: NIDDK).
Some men say certain alternative medicines taken by mouth can help them get and maintain an erection. However, not all “natural” medicines or supplements are safe. Combinations of certain prescribed and alternative medicines could cause major health problems. To help ensure coordinated and safe care, discuss your use of alternative medicines, including use of vitamin and mineral supplements, with a health care professional. Also, never order a medicine online without talking with your doctor.

Whenever I am prescribing a medication to a patient, I’m always asking myself, what can the patient do before requiring the medication? What changes do they have to make in order to reduce the amount of medication or preclude their even needing it? So a good candidate is somebody who has an understanding of a healthy lifestyle, about physical activity, about sleep, about nutrition, alcohol, smoking. So patients, individuals, have to do their share before they’re a candidate for anything. All right?


If you’re experiencing psychological ED, you may benefit from talk therapy. Therapy can help you manage your mental health. You’ll likely work with your therapist over several sessions, and your therapist will address things like major stress or anxiety factors, feelings around sex, or subconscious conflicts that could be affecting your sexual well-being.

The phrase “use it before you lose it” can be applied when it comes to helping men with ED regain normal erectile function. Pelvic exercises, more commonly known as kegel exercises, are used to promote urinary continence and sexual health. They help to strengthen the bulbocavernosus muscle, which does three things: allows the penis to engorge with blood during erection, it pumps during ejaculation, and it helps empty the urethra after urination, according to Healthline.
You’ve probably heard of Viagra, but it’s not the only pill for ED. This class of drugs also includes Cialis, Levitra,  Staxyn, and Stendra. All work by improving blood flow to the penis during arousal. They're generally taken 30-60 minutes before sexual activity and should not be used more than once a day. Cialis can be taken up to 36 hours before sexual activity and also comes in a lower, daily dose. Staxyn dissolves in the mouth. All require an OK from your doctor first for safety.
Additionally, the physiologic processes involving erections begin at the genetic level. Certain genes become activated at critical times to produce proteins vital to sustaining this pathway. Some researchers have focused on identifying particular genes that place men at risk for ED. At present, these studies are limited to animal models, and little success has been reported to date. [4] Nevertheless, this research has given rise to many new treatment targets and a better understanding of the entire process.
medicines called alpha-blockers such as Hytrin (terazosin
HCl), Flomax (tamsulosin HCl), Cardura (doxazosin
mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl),
 Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
Alpha-blockers are sometimes prescribed for prostate
problems or high blood pressure. In some patients, the use
of Sildenafil with alpha-blockers can lead to a drop in blood pressure or to fainting

PD is a chronic neurodegenerative disease characterized by “motor” and “non-motor” symptoms that lead to progressive disability. Erectile and SD are “non-motor” symptoms and can occur in 50–69% of males with PD (39-42). Ejaculatory and orgasmic function are also impaired. PD affects the dopaminergic pathways leading to erection and arousal. Dopaminergic therapy for PD can improve ED, and sometimes therapy may lead to hypersexuality (43,44). A comparison of married men with PD to age matched controls with non-neurologic chronic disease such as arthritis did not show any discrepancy in ED rates (45). This suggests that ED in certain groups with PD may occur from disease related factors common in chronic illness, in general.

The lab testing obtained for the evaluation of erectile dysfunction may vary with the information obtained on the health history, physical examination, and recent lab testing. A testosterone level is not necessary in all men; however, a physician will order labs to determine a patient's testosterone level if other signs and symptoms of hypogonadism (low testosterone) such as decreased libido, loss of body hair, muscle loss, breast enlargement, osteoporosis, infertility, and decreased penile/testicular size are present.

Penile prostheses are very effective, and most patients who have a prosthesis placed are satisfied with the prosthesis. However, placement of a prosthesis causes scarring of the tissue within the corpora cavernosa, and if the prosthesis requires removal, other forms of therapy, except for the vacuum device, are often not effective. Thus, most physicians reserve placement of a prosthesis for men who have tried and failed or have contraindications to other therapies.

Psychosocial problems are important and may cause erectile dysfunction by themselves or together with other causes of erectile dysfunction, such as diabetes and heart disease. Relationships are complicated and many factors cause tensions, which can affect sexual relations. For some men, these problems can become ongoing and it can help to talk through the issue with a skilled counsellor. It is important to know that the longer erectile dysfunction is left untreated, the greater the effect on relationships. This is another reason why early treatment of erectile dysfunction is important.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.
Alprostadil self-injection. With this method, you use a fine needle to inject alprostadil (Caverject Impulse, Edex) into the base or side of your penis. In some cases, medications generally used for other conditions are used for penile injections on their own or in combination. Examples include papaverine, alprostadil and phentolamine. Often these combination medications are known as bimix (if two medications are included) or trimix (if three are included).
Certain street drugs such as "poppers" also can cause serious problems if taken with PDE5i medications. These poppers are often types of nitrates and can cause severe drops in blood pressure. Ecstasy is another street drug that may increase sexual desire but interferes with performance. This has prompted some men to combine ecstasy with PDE5i medications. This mixture (a combination sometimes called "sextasy") can improve erection ability but also causes severe headache and priapism. (Priapism is an abnormally prolonged erection that becomes extremely painful and may result in permanent damage to the erection mechanism.) There are also potentially dangerous effects to your heart from mixing PDE5i medications with various other street drugs.

Sexual functioning involves a complex interaction among biologic, sociocultural, and psychological factors, and the complexity of this interaction makes it difficult to ascertain the clinical etiology of sexual dysfunction. Before any diagnosis of sexual dysfunction is made, problems that are explained by a nonsexual mental disorder or other stressors must first be addressed. Thus, in addition to the criteria for erectile disorder, the following must be considered:
Conditions associated with reduced nerve and endothelium function (eg, aging, hypertension, smoking, hypercholesterolemia, and diabetes) alter the balance between contraction and relaxation factors (see Pathophysiology). These conditions cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defective smooth muscle relaxation. In some patients, sexual dysfunction may be the presenting symptom of these disorders.
PDE5i medications are absolutely not to be taken by men with heart conditions who are taking nitrates such as nitroglycerine or isosorbide (Isordil, Ismo, Imdur). Those with serious heart disease, exertional angina (chest pain), and those taking multiple drugs for high blood pressure are advised to seek the advice of a heart specialist before beginning therapy with sildenafil.
With sex therapy, your counselor looks at the sexual problems you and your partner are having. Sex therapy works with problems such as performance anxiety, which means that you worry so much about whether you will be able to have sex that you are not able to. It also helps when you have erection problems that are not due to physical or drug problems, or premature ejaculation (you come too quickly). It may help you to reach orgasm or to learn to relax enough to avoid pain during sex. Counseling can help you to adjust to the treatment you and your doctor choose.
2 inability of the adult male to achieve or sustain a penile erection or, less commonly, to ejaculate after achieving an erection. Several forms are recognized. Functional impotence has a psychological basis. Organic impotence includes vasculogenic, neurogenic, endocrinic, and anatomical factors. Anatomical impotence results from physically defective genitalia. Atonic impotence involves disturbed neuromuscular function. Poor health, old or advancing age, drugs, smoking, trauma, and fatigue can induce impotence. Also called erectile dysfunction, impotency. impotent, adj.
Normal erectile function depends on the release of NO and endothelial-dependent vasodilation of the penile arteries. The ‘artery size’ hypothesis, first described by Dr Montorsi, offers an explanation why men are more likely to develop ED before a myocardial infacrtion. It is believed that atherosclerosis affects all vascular beds equally but smaller arteries are more likely to become occluded than larger arteries.31 32 The penile arteries are 1–2 mm while the coronary arteries are 3–4 mm. Thus, the same degree of endothelial dysfunction and atherosclerosis is more likely to occlude blood flow in the penile arteries compared with the coronary arteries. The penile arteries therefore serve as a sensitive indicator for subsequent CVD. This theory is supported by the fact that ED occurs approximately 3 years prior to cardiac symptoms in virtually all patients with chronic coronary syndrome whereas patients with acute coronary syndrome have a much lower prevalence of sexual dysfunction.32

Alprostadil, a synthetic PGE1, is the most commonly used single drug for injections into the penis as a treatment for ED. It works well in the majority of men who try it. In one study of 683 men with ED, 94% reported having erections suitable for penetration after PGE1 injections. When PGE1 is used in combination with papaverine and Regitine, the mixture is called Trimix, which has roughly twice the effectiveness of alprostadil alone. However, Trimix is quite expensive and is usually not covered by insurance, while PGE1 is often a covered benefit in most insurance medication plans. The main side effects are pain from the medication (not from the injection), priapism (persistent or abnormally prolonged erection), and scarring at the site of the injection. It is recommended that one alternate the side of the penis being injected to help decrease the risk of penile scarring. Many men are uncomfortable with penile injection therapy even though the injection itself is painless. The injection cannot be done more often than every other day. Men on anticoagulant medications (blood thinners) must be careful with injection therapy.
There are treatments available to help you to get and maintain an erection. In addition, making healthy changes to your lifestyle could help with impotence. Switching to a healthier balanced diet, taking more exercise and cutting down on or giving up alcohol and cigarettes could help you to see an improvement in sexual function. If you think that the problem may be related to stress or anxiety, counselling can also help. 

This inflatable penile prosthesis has 3 major components. The 2 cylinders are placed within the corpora cavernosa, a reservoir is placed beneath the rectus muscle, and the pump is placed in the scrotum. When the pump is squeezed, fluid from the reservoir is transferred into the 2 cylinders, producing a firm erection. The deflation mechanism is also located on the pump and differs by manufacturer.
In general, PDE5i works successfully in about 65%-70% of all men with erectile dysfunction (impotence). The greater the degree of damage to the normal erection mechanism and severity of the ED, the lower the overall success rate. Men with diabetes and those with spinal cord injury reported between 50%-60% responding successfully to treatment with oral PDE5i medications. The lowest success rate has been in men who developed ED (impotence) after prostate cancer surgery (radical prostatectomy) for more advanced prostate cancer that required removal of both sets of nerves around the prostate. In men who did not have the nerves removed/damage, there is a better chance of response to PDE5 inhibitors.
Erectile dysfunction is only one cause of sexual dysfunction. Other causes of sexual dysfunction include troubles with ejaculation, decreased libido, and troubles achieving an orgasm (climax). Some men may have premature ejaculation, which is a condition in which the entire process of arousal, erection, ejaculation, and climax occur very rapidly, often in just a few minutes or even seconds, leaving the partner unsatisfied. Premature ejaculation may accompany an erection problem such as ED but is generally treated differently. Troubles with erectile function may lead to decreased libido or interest in sex, however, many men with decreased libido have normal erectile dysfunction. Libido may be affected by psychologic factors, such as stress, anxiety, or depression but often is the result of a low testosterone (the male hormone) level.
Replacement testosterone is available as oral pills, intramuscular injections, skin patches, and a gel that is rubbed into the skin. Men with low sexual desire and ED may have low testosterone (male hormone) levels. Hormone replacement may occasionally be of some benefit, especially when used in combination with other therapies. Testosterone supplementation alone is not particularly effective in treating erectile dysfunction. Sexual desire and an overall sense of well-being are likely to improve when serum testosterone levels (the levels in the blood) are restored. This can take several months after starting testosterone replacement.

medicines called alpha-blockers such as Hytrin (terazosin
HCl), Flomax (tamsulosin HCl), Cardura (doxazosin
mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl),
 Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
Alpha-blockers are sometimes prescribed for prostate
problems or high blood pressure. In some patients, the use
of Sildenafil with alpha-blockers can lead to a drop in blood pressure or to fainting


Erectile dysfunction (ED) affects 50% of men older than 40 years, [4] exerting substantial effects on quality of life. [5] This common problem is complex and involves multiple pathways. Penile erections are produced by an integration of physiologic processes involving the central nervous, peripheral nervous, hormonal, and vascular systems. Any abnormality in these systems, whether from medication or disease, has a significant impact on the ability to develop and sustain an erection, ejaculate, and experience orgasm.

Dr Kenny du Toit is a urologist practicing in Rondebosch, Cape Town. He is also consultant at Tygerberg hospital, where he is a senior lecturer at Stellenbosch University. He is a member of the South African Urological Association, Colleges of Medicine South Africa and Société Internationale d’Urologie. Board registered with both the HPCSA (Health professions council of South Africa) and GMC (General medical council UK). He has a keen interest in oncology, kidney stones and erectile dysfunction.http://www.dutoiturology.co.za
Injection therapy: The modern age of such drug therapies began in 1993 when the injection of papaverine (Pavabid), an alpha-blocker that produces vasodilatation (widening of the blood vessels), was shown to produce erections when injected directly into the penis. Soon afterward, other vasodilators, such as prostaglandin E1 (PGE 1) monotherapy (Caverject, Edex), PGE1 and phentolamine (Regitine), and Trimix (papaverine, phentolamine and prostaglandin E1), were demonstrated to be effective. The benefit of combination therapy is the decreased dosing of each with less side effects. Most important is the reduction of the prostaglandin PGE1 dosing, which is associated to the localized pain.

Since endothelial dysfunction, CVD and ED are closely associated in epidemiological studies, the question for clinicians is whether to recommend the man presenting with ED undergo a cardiovascular (CV) evaluation. Clearly, based on numerous studies, ED can be considered at least a ‘marker’ for possible further vascular disease or CVD.15 In their report, Vlachopoulos and coworkers make the point that the man presenting with ED, the clinician, is offered an opportunity to attempt to improve the health of the man by addressing lifestyle modification, and consider further vascular evaluation owing to the clear relationship between endothelial dysfunction, ED and CVD.19


Recently, several advances in the uses of stem cells have bet met with great anticipation. Stem cells have the ability to differentiate into different cell lines based on the cellular signaling they receive. Bone marrow mononuclear cells in particular have been used for the treatment of ED in animal models. Yiou et al. recently delivered bone marrow-mononuclear cells (BM-MNC) into the intracavernous smooth muscle of post radical prostatectomy men (123). The open label, dose escalation phase I/II trial showed improvements in IIEF-15 assessment as well as increased vascularization of the corpora based on penile Doppler arterial velocity measurements. Although promising, further investigation in humans is required to substantiate BM-MNCs impact on erections, and erectile function recovery going forward.
Monitoring erections that occur during sleep (nocturnal penile tumescence) can help you and your doctor to understand if the erectile dysfunction is due to psychological or physical causes. The nocturnal penile tumescence test is a study to evaluate erections at night. Normally men have three to five erections per eight hours of sleep. The test can be performed at home or in a sleep lab. The most accurate way to perform the test involves a special device that is connected to two rings. The rings are placed around the penis, one at the tip of the penis and the other at the bottom (base) of the penis. The device records how many erections occur, how long they last, and how rigid they are. The test is limited in that it does not assess the ability to penetrate.
When sexually stimulated there is a release of a chemical, nitric oxide (NO) in the blood vessels of the corpus cavernosum. The NO stimulates the production of a compound called cGMP, which causes relaxation of the smooth muscle in the blood vessels supplying the corpus cavernosum. PDE 5 is an enzyme that breaks down cGMP. By inhibiting the breakdown of cGMP by PDE5, these medications allow cGMP to build up in the penis. cGMP causes muscles in the corpora cavernosa of the penis to relax. When the muscle is relaxed, more blood can flow into the penis and fill the spaces in the penis. As the penis fills with blood, the veins in the penis are compressed, and this results a hard erection. When the effect on PDE5 decreases, the cGMP levels go down and the muscle in the penis contracts, causing less blood to flow into the penis and allowing the veins to open up and drain blood out of the penis.
Self-injection of these agents has been of enormous benefit because they represent the most effective way to achieve erections in a wide variety of men who otherwise would be unable to achieve adequate rigid erections. The need for intact nerve pathways to the penile tissue is not needed. The locally injected medication directly relaxes the arteriole vessels and penile cavernosal tissue. Thus, this therapy is not dependent on sexual stimulation.
Proper informed consent with your physician should be performed to understand all risks and benefits of hormonal replacement therapy. Follow-up testosterone (hormone) levels and periodic blood counts as testosterone therapy is associated with a risk of an abnormally high red blood cell count, and prostate checks are necessary for all men on long-term testosterone replacement therapy as there are concerns regarding the risk of testosterone therapy in men with an underlying prostate cancer. The use of testosterone therapy does not cause the development of prostate cancer. Testosterone therapy may increase the size of the prostate and cause urinary troubles.
Between 10 and 88% of patients diagnosed with cancer experience sexual problems following diagnosis and treatment. The prevalence varies according to the location and type of cancer, and the treatment modalities used. Sexuality may be affected by chemotherapy, alterations in body image due to weight change, hair loss or surgical disfigurement, hormonal changes, and cancer treatments that directly affect the pelvic region.
Conditions associated with reduced nerve and endothelium function (eg, aging, hypertension, smoking, hypercholesterolemia, and diabetes) alter the balance between contraction and relaxation factors (see Pathophysiology). These conditions cause circulatory and structural changes in penile tissues, resulting in arterial insufficiency and defective smooth muscle relaxation. In some patients, sexual dysfunction may be the presenting symptom of these disorders.

Erections occur in response to tactile, olfactory, and visual stimuli. The ability to achieve and maintain a full erection depends not only on the penile portion of the process but also on the status of the peripheral nerves, the integrity of the vascular supply, and biochemical events within the corpora. The autonomic nervous system is involved in erection, orgasm, and tumescence. The parasympathetic nervous system is primarily involved in sustaining and maintaining an erection, which is derived from S2-S4 nerve roots.


Men can judge themselves pretty harshly when it comes to their performance in between the sheets. The unsettling fear of not being able to rise to the occasion becomes a reccurring nightmare for men that is often equated with failure, loss of dignity, and masculinity. If you suffer from erectile dysfunction (ED), don’t be so hard on yourself, since impotence can almost always be improved with treatment, without having to rely on Viagra or other medications. Whether you suffer from ED, or hope to prevent the condition, here are six tips to overcome impotence without the side effects of the little blue pill.

Associated morbidity may include various other male sexual dysfunctions, such as premature (early) ejaculation and male hypoactive sexual desire disorder. The NHSLS found that 28.5% of men aged 18-59 years reported premature ejaculation, and 15.8% lacked sexual interest during the past year. An additional 17% reported anxiety about sexual performance, and 8.1% had a lack of pleasure in sex. [51]
In the Massachusetts Male Aging Study (MMAS) among a community-based survey of men aged 40-70 years, 52% of the men reported some degree of erectile difficulty. Complete ED, defined as the total inability to obtain or maintain suitable erections during sexual stimulation, as well as the absence of nocturnal erections (normal erections [four to six/night], which occur during sleep), occurred in 10% of the men in the study. Lesser degrees of mild and moderate ED occurred in 17% and 25% of participants.
Quitting smoking, exercising regularly, losing excess weight, curtailing excessive alcohol consumption, controlling hypertension, and optimizing blood glucose levels in patients with diabetes are not only important for maintaining good health but also may improve or even prevent progression of erectile dysfunction. It is unclear if such lifestyle changes can reverse erectile dysfunction. However, lifestyle improvements may prevent progression of the erectile dysfunction. Some studies suggest that men who have made lifestyle improvements experience increased rates of success with oral medications.
Positron emission tomorgraphy (PET), and functional magnetic resonance imaging (fMRI) have led to a greater understanding to which center are activated during arousal. These imaging studies measure increases in cerebral blood flow or changes in cerebral activity on a real-time basis. Studies are performed when male subject are aroused by visual cues (usually sexual explicit photos or videos) and compared to images obtained during exposure to sexually neutral cues differences can be measured. Several studies have identified that the inferior frontal lobes, inferior temporal lobes and insular gyrus, and occipital lobes are involved with processing arousal cues, although each are likely to process different stimuli (20-23).
Somatomotor penile innervation originates in Onuf’s nucleus in the S2-4 spinal segments. These nerves travel to the ischiocavernosus and bulbocavernosus muscles when activated lead to contraction necessary for the rigid-erection phase. Several animal studies show that stimulation of the somatomotor pathways may also be under sympathetic control, and adrenergic stimulation may lead to contraction of these muscles during ejaculation (13,14). Somatomotor spinal reflexes may also be initiated by genital stimulation. For instance, the well-known bulbocavernosus reflex is evidence this reflex exists; however the clinical significance of its absence in the neurological assessment of ED has not been substantiated (15).
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

The penis is composed of three cylinders, two on the top and one on the underside of the penis. The top two cylinders are involved in the erectile process. The urethra, the tube that urine and semen pass through, is on the underside of the penis. The top two penile cylinders, the corpora cavernosa, are composed of tissue that is analogous to a sponge, containing spaces that can fill with blood and expand. These two cylinders are surrounding by a strong layer of tissue, like Saran wrap, the tunica albuginea. For an erection to occur, there must be properly functioning nerves, arteries, veins, and normal penile tissues.
PD is a chronic neurodegenerative disease characterized by “motor” and “non-motor” symptoms that lead to progressive disability. Erectile and SD are “non-motor” symptoms and can occur in 50–69% of males with PD (39-42). Ejaculatory and orgasmic function are also impaired. PD affects the dopaminergic pathways leading to erection and arousal. Dopaminergic therapy for PD can improve ED, and sometimes therapy may lead to hypersexuality (43,44). A comparison of married men with PD to age matched controls with non-neurologic chronic disease such as arthritis did not show any discrepancy in ED rates (45). This suggests that ED in certain groups with PD may occur from disease related factors common in chronic illness, in general.
Prevention of some of the causes that contribute to the development of erectile dysfunction can decrease the chances of developing the problem. For example, if a person decreases their chances of developing diabetes, heart disease, and hypertension, they will decrease their chances of developing erectile dysfunction. Other things like stopping smoking, eating a healthy diet (heart healthy with adequate vitamin intake), and exercising daily may reduce a person's risk.
The mechanisms by which testosterone plays a role in erectile function are not completely understood. A study evaluating the effect of testosterone on erections in surgically castrated rabbits and control animals, in which the rabbits’ intracavernosal pressures were compared after cavernosal nerve stimulation, determined that castrated rabbits had much lower pressures after stimulation than control rabbits did. [21] Notably, the pressures increased when castrated rabbits received exogenous testosterone replacement.
Erections occur in response to tactile, olfactory, and visual stimuli. The ability to achieve and maintain a full erection depends not only on the penile portion of the process but also on the status of the peripheral nerves, the integrity of the vascular supply, and biochemical events within the corpora. The autonomic nervous system is involved in erection, orgasm, and tumescence. The parasympathetic nervous system is primarily involved in sustaining and maintaining an erection, which is derived from S2-S4 nerve roots.

PDE5i for ED in patients with MS can be considered as reasonably effective and safe. Fowler et al. performed a randomized, multicenter, double-blind, flexible dose trial with open label extensions comparing sildenafil to placebo (75). A nearly 4-fold increase in effective erections was noted in the treatment arm, 96% vs. 24%. Sexual satisfaction and overall satisfaction were also improved in the treatment group based on IIEF scores, and quality of life assessments. Lombardi et al. evaluated tadalafil use in men with MS (71). Seventy eight percent of the men responded with improved erections, better quality of life with regards to sexual function, partner relationship and family life. Just less than half the men who responded to the tadalafil did so at the lower dosage of 10 mg. Subjects in either studies did not have any significant adverse side effects beyond flushing, and headache with PDE5i use.
Besides PDE5 inhibitors and among second-line therapies are VCDs which are clear plastic chambers placed over the penis, tightened against the lower abdomen with a mechanism to create a vacuum inside the chamber. This directs blood into the penis. If an adequate erection occurs inside the chamber, the patient slips a small constriction band off the end of the VCD and onto the base of the penis. An erection beyond 30 min is not recommended. These devices can be a bit cumbersome, but are very safe.40
It is estimated that up to 20 million American men frequently suffer from impotence and that it strikes up to half of all men between the ages of 40 and 70. Doctors used to think that most cases of impotence were psychological in origin, but they now recognize that, at least in older men, physical causes may play a primary role in 60% or more of all cases. In men over the age of 60, the leading cause is atherosclerosis, or narrowing of the arteries, which can restrict the flow of blood to the penis. Injury or disease of the connective tissue, such as Peyronie's disease, may prevent the corpora cavernosa from completely expanding. Damage to the nerves of the penis, from certain types of surgery or neurological conditions, such as Parkinson's disease or multiple sclerosis, may also cause impotence. Men with diabetes are especially at risk for impotence because of their high risk of both atherosclerosis and a nerve disease called diabetic neuropathy.

The availability of phosphodiesterase-5 (PDE5) inhibitors—sildenafil, vardenafil, tadalafil, and avanafil—has fundamentally altered the medical management of ED. In addition, direct-to-consumer marketing of these agents over the last 15 years has increased the general public’s awareness of ED as a medical condition with underlying causes and effective treatments.

Years ago, the standard treatment for impotence was an implantable penile prosthesis or long-term psychotherapy. Although physical causes are now more readily diagnosed and treated, individual or marital counseling is still an effective treatment for impotence when emotional factors play a role. Fortunately, other approaches are now available to treat the physical causes of impotence.
I would think the 25% is just an average. Some men never have a problem with erections. Some healthy men in their 60's never have a problem with their erections -- no Viagra needed at all, thank you. And, no, it is NOT completely associated with age. In fact, many men in their 40's and even younger, are already dealing with ED, especially if they smoke, are obese, don't exercise, or are addicted to porn, among other things. In fact, even men in their 20's and 30's can have these problems.
In a prospective study from the Prostate Cancer Prevention Trial database, Thompson et al reported that men presenting with ED had a significantly higher chance of developing a cardiovascular event over a 7-year follow-up period. [55] The hazard ratio was 1.45, which is in the range of risk associated with current smoking or a family history of MI.

"The good news is, our study also found that a large proportion of men were naturally overcoming erectile dysfunction issues. The remission rate of those with erectile dysfunction was 29%, which is very high. This shows that many of these factors affecting men are modifiable, offering them an opportunity to do something about their condition," Professor Wittert says.
One of the first steps is to distinguish between physiological and psychological ED. Determining whether involuntary erections are present is important in eliminating the possibility of psychogenic causes for ED.[2] Obtaining full erections occasionally, such as nocturnal penile tumescence when asleep (that is, when the mind and psychological issues, if any, are less present), tends to suggest that the physical structures are functionally working.[19][20] Similarly, performance with manual stimulation, as well as any performance anxiety or acute situational ED, may indicate a psychogenic component to ED.[2]
Injections are most likely to restore testosterone levels, but this therapy requires periodic injections, usually every two to four weeks, to sustain an effective level. As such, it is less ideal for patients to depend on frequent medical visits for long-duration therapy. Coupled with injection-related pain, hematoma formation, and inconvenience, the serum blood levels of testosterone are also variable. Injection therapy should not be used in men who wish to father children due to the abnormally high levels of testosterone that occur initially after the injection.
Penile prosthesis is the primary form of surgical therapy and is reserved for those men who fail, are intolerant of, or have contraindications to other forms of therapy. Currently, there are several different types of penile prostheses. The simplest is the malleable penile prosthesis, and the most complex is the three-piece inflatable penile prosthesis.
Erectile dysfunction is the inability to develop or maintain an erection that is rigid enough to allow penetration of the vagina, and therefore functional sexual intercourse. Generally, the term erectile dysfunction is applied if this occurs frequently (75% of the time) over a significant period if time (several weeks to months). If this is the case, the term impotence may also be used.
3. An intact, anatomically correct penis; 25% of impotence may be psychologic or 'partner-specific', 25% has an organic component and 50% of impotence is organic in nature; in organic impotence, nocturnal penile tumescence is absent Management-surgical Microvascular surgery to bypass occluded vessels–most effective in younger ♂, penile prosthesis Management-medical Combined therapy with phentolamine and papaverine–self-injected by the Pt, wielding an erection of 1 hr's duration is useful for arterial, neurologic, psychogenic impotence; other therapies–zinc, bromocriptine–Parlodel, isoxsuprine-Vasodilan, Voxsuprine, nitroglycerine, yohimbine–Yocon, Yohimex Etiology Smoking, CAD, HTN, DM, medications–hypoglycemic agents, vasodilators, cardiac drugs, antihypertensives, anger and depression; it is inversely correlated to dehydroepiandrosterone, HDL-C, and an index of dominant personality Primary impotence Complete absence of successful sexual coupling Secondary impotence Priapism, penile plaques, Peyronie's disease; drugs linked to impotence: antihypertensives–eg, methyldopa, guanethidine, reserpine, clonidine, due to ↓ BP, antidepressants–eg, phenelzine, isocarboxazide, amitriptyline–causing altered moods and decreased libido, tranquilizers–eg, chlordiazepoxide and lorazepam, and the muscle-relaxing diazepam, cimetidine, which ↑ prolactin, and is associated with impotence and loss of libido. Cf Infertility, Orgasmic dysfunction.

These are not currently approved by the FDA for ED management, but they may be offered through research studies (clinical trials). Patients who are interested should discuss the risks and benefits (informed consent) of each, as well as costs before starting any clinical trials. Most therapies not approved by the FDA are not covered by government or private insurance benefits.
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