Parasympathetic pathways originate from the intermediolateral cell columns of the 2nd, 3rd and 4th sacral spinal cord segments. Preganglionic fibers pass through the pelvic plexus where they coalesce with sympathetic fibers from the superior hypogastric plexus. The cavernous nerves that innervate the penis arise from the portion of the pelvic plexus. The pelvic plexus also contains nerves that innervate the rectum, bladder and urinary sphincter and the nerve projections can be damaged during radical excision of the bladder, prostate and rectum, leading to iatrogenic ED (4).
Some self-administered measures may be useful in the primary care setting to screen for and evaluate the degree of ED.12 The most commonly used instrument is the International Index of Erectile Function, a 15-item questionnaire that has been validated in many populations and is considered the gold standard to evaluate patients for ED.13 The Sexual Health Inventory for Men is a short-form, 5-item questionnaire developed to monitor treatment progress.12 It is important to recognize that short-form questionnaire does not evaluate specific areas of the sexual cycle, such as sexual desire, ejaculation, and orgasm; however, it may be useful in discussing ED with patients and evaluating treatment results over time.
Before taking any medication for erectile dysfunction, including over-the-counter supplements and herbal remedies, get your doctor's OK. Medications for erectile dysfunction do not work in all men and might be less effective in certain conditions, such as after prostate surgery or if you have diabetes. Some medications might also be dangerous if you:
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?

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).
With drug therapy, there’s a risk of side effects such as headaches, back pain or an upset stomach. Before taking any medication for erectile dysfunction it is important to ensure your doctor is ok with that decision. Medication may not work for all men, for instance, if you have diabetes or have previously had prostate surgery. ED medication might also have serious risks if you’re currently taking nitrates (commonly prescribed for chest pain), have heart disease or have low blood pressure.22
The association between low testosterone and ED is not entirely clear. Although these 2 processes certainly overlap in some instances, they are distinct entities. Some 2-21% of men have both hypogonadism and ED; however, it is unclear to what degree treating the former will improve erectile function. [17] About 35-40% of men with low testosterone see an improvement in their erections with testosterone replacement; however, almost 65% of these men see no improvement. [15]

Alprostadil is a potent vasodilator and smooth muscle relaxant identical to the naturally occurring PGE1. PGE1 binds with specific receptors on smooth muscle cells and activates intracellular adenylate cyclase to produce cAMP, which in turn induces tissue relaxation through a second messenger system (96). PGE1 is the only FDA approved form of intracavernosal therapy and is available commercailly as EDEX, or Caverject. Its efficacy was demonstrated in several clinical trials where the rate of responders ranged from 40% to 80% (97,98). The most common adverse event is penile pain, which is not related to the injection of the medication itself. In men with prolonged use the pain is usually self-limited (99).
All of these medicines work by relaxing smooth muscles and increasing blood flow in the penis during sexual stimulation. You should not take any of these medicines to treat ED if you are taking nitrates to treat a heart condition. Nitrates widen and relax your blood vessels. The combination can lead to a sudden drop in blood pressure, which may cause you to become faint or dizzy, or fall, leading to possible injuries.
For obvious reasons, ED can be a sensitive subject, one that until relatively recently men were more likely to try to hide than to deal with. Fortunately, a deeper understanding of the variety of causes of erectile dysfunction has led to medications, therapies, and other treatments that can be more individualized and more likely to be effective—and more open discussion about addressing the concern.

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).
In a randomized double-blind, parallel, placebo-controlled trial, sildenafil plus testosterone was not superior to sildenafil plus placebo in improving erectile function in men with ED and low testosterone levels. [19] The objective of the study was to determine whether the addition of testosterone to sildenafil therapy improves erectile response in men with ED and low testosterone levels.

Parasympathetic pathways originate from the intermediolateral cell columns of the 2nd, 3rd and 4th sacral spinal cord segments. Preganglionic fibers pass through the pelvic plexus where they coalesce with sympathetic fibers from the superior hypogastric plexus. The cavernous nerves that innervate the penis arise from the portion of the pelvic plexus. The pelvic plexus also contains nerves that innervate the rectum, bladder and urinary sphincter and the nerve projections can be damaged during radical excision of the bladder, prostate and rectum, leading to iatrogenic ED (4).
In some cases, ED can be a warning sign of more serious disease. One study suggests ED is a strong predictor of heart attack, stroke, and death from cardiovascular disease. The researchers say all men diagnosed with ED should be evaluated for cardiovascular disease. This does not mean every man with ED will develop heart disease, or that every man with heart disease has ED, but patients should be aware of the link.
The dorsal artery provides for engorgement of the glans during erection, whereas the bulbourethral artery supplies the bulb and the corpus spongiosum. The cavernous artery effects tumescence of the corpus cavernosum and thus is principally responsible for erection. The cavernous artery gives off many helicine arteries, which supply the trabecular erectile tissue and the sinusoids. These helicine arteries are contracted and tortuous in the flaccid state and become dilated and straight during erection. [9]
Learn more about sex. If you have deep-rooted anxieties or guilt related to sex, these negative emotions might be causing your ED. Learning more about sex can be a good way to feel more comfortable with your body and better understand your needs in bed.[8] Read up on sex techniques or take a sex-positive workshop as a way to open your mind to new possibilities and increase your comfort level.
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).
This is similar to magnetic resonance imaging. Magnetic resonance angiography uses magnetic fields and radio waves to provide detailed images of the blood vessels. Doctors may inject a "contrast agent" into the person's bloodstream that causes vascular tissues to stand out against other tissues. The contrast agent provides for enhanced information regarding blood supply and vascular anomalies.
Medications such as sildenafil (Viagra), vardenafil (Levitra), or tadalafil (Cialis) may help improve sexual function in men by increasing blood flow to the penis. Men who are on medicines that contain nitrates such as nitroglycerine should not take oral ED medications. The combination of nitrates and these specific medications can cause low blood pressure (hypotension).
Experiencing ED can also be a reason to try not penetrative sex.  Try planning a sex session with your partner hat isn't focused on your erection at all.  Things like kissing, licking, sucking, foreplay and teasing all are super stimulating and don't focus on penetration.  Feel free to bring each other to orgasm using these ideas and see if you are able to relax and enjoy the experience.  Many men feel like failures when their erections become unreliable.  Having a few successful sexual sessions that lead to orgasm without penetration can put the fun back into having sex.  Many couples find success using this technique and begin to reengage sexually instead of avoiding being sexual for fear of failure.
If you have symptoms of ED, it’s important to check with your doctor before trying any treatments on your own. This is because ED can be a sign of other health problems. For instance, heart disease or high cholesterol could cause ED symptoms. With a diagnosis, your doctor could recommend a number of steps that would likely improve both your heart health and your ED. These steps include lowering your cholesterol, reducing your weight, or taking medications to unclog your blood vessels.
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.
Erectile dysfunction is defined as the persistent inability to achieve or maintain penile erection sufficient for satisfactory sexual performance. The Massachusetts Male Aging Study surveyed 1,709 men aged 40–70 years between 1987 and 1989 and found there was a total prevalence of erectile dysfunction of 52 percent. It was estimated that, in 1995, over 152 million men worldwide experienced ED. For 2025, the prevalence of ED is predicted to be approximately 322 million worldwide.
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).
Learn more about sex. If you have deep-rooted anxieties or guilt related to sex, these negative emotions might be causing your ED. Learning more about sex can be a good way to feel more comfortable with your body and better understand your needs in bed.[8] Read up on sex techniques or take a sex-positive workshop as a way to open your mind to new possibilities and increase your comfort level.
ED usually has a multifactorial etiology. Organic, physiologic, endocrine, and psychogenic factors are involved in the ability to obtain and maintain erections. In general, ED is divided into 2 broad categories, organic and psychogenic. Although most ED was once attributed to psychological factors, pure psychogenic ED is in fact uncommon; however, many men with organic etiologies may also have an associated psychogenic component.
								   Impotence, also known as erectile dysfunction or ED, is a condition in which a man is unable to get or hold an erection long enough to have a satisfactory sex life. Impotence is a common problem, affecting up to half of Australian men between the ages of 40 and 70 years. The risk of developing erectile dysfunction increases as you get older.In the past, doctors considered impotence to be a mainly psychological problem, caused by performance anxiety or stress. Now, doctors know that many cases of impotence have a physical cause, which usually can be treated. Often, a combination of physical and psychological factors contributes to erectile dysfunction.Physical causes of impotencePhysical causes of impotence can include:problems with blood to flow into and out of the penis;damage to the nerves that send signals from the body’s central nervous system to the penis; and, more rarely,a deficiency in testosterone or other hormones.Some medicines can contribute to impotence, as can some types of surgery and radiotherapy treatments.Blocked blood vessels to the penisA very common cause of impotence is when blood flow into the penis is reduced. This can be due to atherosclerosis, also known as hardening of the arteries. In atherosclerosis, the arteries are clogged and narrowed, resulting in reduced blood flow.Risk factors for atherosclerosis include:high cholesterol;high blood pressure;obesity;sleep apnoea;diabetes; andsmoking.If your erection problems are caused by atherosclerosis, there is a chance that the arteries in other parts of your body (e.g. the coronary arteries that supply your heart) are also affected by atherosclerosis. In fact, erection problems may be the first sign that you are at risk of coronary heart disease.Because the arteries to the penis are narrower than those to the heart, you may develop symptoms of erectile dysfunction before you experience any symptoms of heart disease, such as angina. So seeing your doctor about erection problems may be important for your overall physical health.Impotence can also be caused by a blood clot that prevents enough blood from flowing into the penis to cause an erection.Venous leakageIn some men, blood can flow in to the penis easily, but the problem is that it leaks out again, so an erection cannot be sustained. This is called venous leakage. Doctors aren’t certain of the cause of venous leakage, but they can perform surgery to help repair it.Medicines that can cause impotenceMany medicines can cause erection problems as a side effect, including:diuretics (sometimes known as ‘water tablets’ - often used for high blood pressure);high blood pressure medications;cholesterol-lowering medicines (including statins);some types of antipsychotics;antidepressants;cancer treatments;some medicines used to treat heartburn and stomach ulcers;antihistamines;some pain medicines; andcertain epilepsy medications.If you experience impotence after starting a new medication, tell your doctor, who may be able to prescribe a different medicine for you. Don’t stop taking a medicine without first consulting your doctor. You should also tell your doctor about any over-the-counter medicines or complementary remedies you may be taking.The following table contains a list of specific medicines that may cause or contribute to erectile dysfunction. This list may not cover all types of medicines that can cause erectile dysfunction, so always ask your doctor if you are in doubt. Also, for some of these medicines ED is a very rare side effect. Most men taking these medicines do not experience erectile dysfunction.Medicines that may cause erectile dysfunctionType of medicineExamplesACE inhibitorscaptopril (Capoten), enalapril (Renitec), perindopril (Perindo), ramipril (Tritace), and othersAntidepressantsamitriptyline (Endep), clomipramine (Anafranil), desvenlafaxine (Pristiq), fluoxetine (Prozac), paroxetine (Aropax), sertraline (Zoloft), venlafaxine (Altven, Efexor), and othersAnti-epilepticsclonazepam (Rivotril), pregabalin (Lyrica)Antifungalsitraconazole (Sporanox)Anti-ulcer drugscimetidine (Magicul), nizatidine (Tazac), ranitidine (Zantac), and othersBeta-blockerspropranolol (Inderal), metoprolol (Betaloc, Lopresor), and othersOther blood pressure-lowering medicinesclonidine (Catapres), lercanidipine/enalapril (Zan-Extra), losartan (Cozaar), perindopril/amlodipine (Coveram), olmesartan/amlodipine (Sevikar), telmisartan/amlodipine (Twynsta), valsartan/hydrochlorothiazide (Co-Diovan)Calcium-channel blockersdiltiazem (Cardizem), felodipine (Plendil), nifedipine (Adalat)Cholesterol-lowering drugsatorvastatin (Lipitor), ezetimibe/simvastatin (Vytorin), fluvastatin (Lescol, Vastin), gemfibrozil (Ausgem), pravastatin (Pravachol), simvastatin (APO-simvastatin, Lipex, Zocor), and othersDiuretics ('water tablets')bumetanide (Burinex), chlorthalidone (Hygroton), spironolactone (Aldactone), and othersSchizophrenia drugsamisulpride (Solian, Sulprix), haloperidol (Haldol, Serenace), olanzapine (Lanzek, Ozin, Zypine, Zyprexa), paliperidone (Invega), risperidone (Rispa, Risperdal), ziprasidone (Zeldox)Combination cholesterol-lowering and anti-hypertensiveamlodipine/atorvastatin (Caduet, Cadatin)Pain medicinesfentanyl (Denpax, Durogesic), hydromorphone (Jurnista), morphine (Momex SR, MS Contin), oxycodone (OxyContin, OxyNorm, Targin), tramadolMiscellaneousoestrogens, antiandrogens, anticancer drugs and some chemotherapy treatments, baclofen (Clofen, Lioresal); cyproterone (Androcur, Cyprohexal, Cyprostat), degarelix (Firmagon), etoricoxib (Arcoxia), finasteride (Proscar and Propecia), flutamide (Flutamin), rotigotine (Neupro), triptorelin (Diphereline)*The names in brackets are just some examples of the trade names each specific medicine is marketed under in Australia. The medicine may also be known by other trade names.Diabetes and erectile dysfunctionMen who have diabetes have a higher risk of developing impotence than other men. Diabetes contributes to impotence because it can damage blood vessels and cause a type of nerve damage known as peripheral neuropathy.Hormones and impotenceLow levels of the male hormone, testosterone, are more commonly linked to a lowered sex drive, rather than impotence itself. Only a small percentage of cases of impotence are caused by hormone deficiency.Low testosterone levels may be the result of a condition called hypogonadism, in which the testicles don’t produce enough testosterone. More rarely, low testosterone can be caused by the pituitary (a small gland at the base of the brain) not secreting sufficient hormones to stimulate the testes to produce testosterone. The pituitary is also sometimes affected by small benign (non-cancerous) tumours that secrete prolactin, another hormone that can cause impotence.Mildly decreased levels of testosterone are often not due to specific testicular or pituitary problems, but rather stress or depression. In this situation, testosterone replacement is rarely of any benefit.Other hormone problems, including thyroid disease, can also cause impotence.Prostate cancer and erectile dysfunctionThe advanced stages of prostate cancer can affect the nerves and arteries that are vital for an erection.Radiation treatment for prostate cancer can harm the erectile tissues of the penis, and prostate cancer surgery can cause nerve or artery damage to the penis.Treatment for advanced prostate cancer often includes medicines that counteract testosterone, and commonly cause erectile dysfunction as well as loss of sexual interest.Peyronie’s diseasePeyronie’s disease is an uncommon condition that affects a man’s sex life because his penis curves abnormally and causes pain when he has an erection. He might also be unable to have a hard erection. The curvature of the penis is caused by a scar, called a plaque, that forms in the penis.Other physical causes of impotenceSeveral other factors and conditions can contribute to erectile dysfunction, including the following.Depression. Many men find that when they’re suffering from depression, they lose interest in sex and can’t get or keep an erection. Asking your doctor for treatments for depression may help alleviate your erection problems as well.Smoking contributes to vascular disease (disease of the blood vessels), so it can contribute to erectile dysfunction by affecting blood flow to the penis. Giving up smoking often has a beneficial effect on erectile function.Excessive alcohol use. Alcoholism can cause permanent nerve damage, resulting in impotence. This nerve damage is called peripheral neuropathy. Long-term alcohol use can impair the liver’s ability to function, resulting in a hormone imbalance in which a man has too much of the female sex hormone, oestrogen. On a day-to-day level, alcohol dulls the central nervous system, adversely affecting sexual response.Illicit drug use. Illicit drugs such as marijuana, cocaine, heroin, barbiturates, and amphetamines act on the central nervous system, impairing the body’s ability to respond sexually.Certain exercises. Nerve and artery damage can be caused by prolonged cycling, rodeo riding, or use of a rowing machine, resulting in the inability to get an erection. Often, minimising the use of hard bicycle seats and exercise machine seats, as well as correct positioning of the seat, will help restore sexual function.Surgery to organs near the nerve pathways of the penis, such as the bladder, rectum and prostate, can cause nerve or artery damage to the penis, resulting in the inability to have an erection.Injuries. Impotence can be caused by spinal cord injury; injury to your sex organs; or a pelvic fracture, which can cause damage to the nerves of the penis, or damage the blood vessels, resulting in reduced blood flow to the penis.Conditions affecting the nervous system. Multiple sclerosis (MS) and other degenerative diseases of the nervous system, such as Parkinson’s disease, can damage the nerves involved in erections.Psychological causes of impotenceMost cases of impotence have physical causes, but, in some men, psychological factors are the main contributors to impotence.Impotence that’s triggered by psychological factors is more common in men who are sexually inexperienced. Psychological erectile dysfunction may only occur when you’re with just one particular person. You’re also more likely to have morning erections, and be able to have an erection when you masturbate, than men whose impotence has a physical cause.Here are some psychological factors that can have an impact on your erections.Stress and anxietyWhen you’re stressed and focusing on other issues apart from sex, you might find that you don’t want to have sex as often and there might be a drop in your ability to perform when you do try. You might find that tackling the source of your stress can have benefits in the bedroom as well.Fear of failureAnxiety about your sexual prowess (commonly called performance anxiety) can, in itself, contribute to failure. By putting pressure on yourself, you become too anxious to get an adequate erection.Most men experience isolated episodes of erectile failure. Even when the transient physical cause has passed, anxiety that it may recur is sufficient to prevent erection. Anxiety, whether about something specifically sexual or part of a wider anxiety syndrome, is never helpful to good sexual function.Problems with your relationship and impotenceImpotence may be a manifestation of a poor relationship, or a problematic time in a relationship. Sexual boredom, tension or anger among partners, and lack of intimacy and communication are all possible triggers of erectile dysfunction. In these cases, seeing a counsellor may help.It’s worth remembering that impotence is a complex medical condition, which may have more than one cause. For example, if impotence is the result of a side effect of medicine or an underlying disease, the anxiety caused by lack of performance may perpetuate the erectile dysfunction even after the physical cause has been dealt with.Almost any chronic (ongoing) physical or mental health disorder, including those with no direct effect on penile nerves or blood supply, can have a powerful effect on sexuality, sexual self-image and erectile function.If you’re worried about your sexual response or the quality of your erections, don’t be afraid to talk to your doctor, who has access to treatments that can help. Last Reviewed: 16 December 2016 

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Soler et al. compared sildenafil to vardenafil and tadalafil (69). Sildenafil was effective in 85% of SCI patients, 74% of the patients on vardenafil and 72% of the patients on tadalafil. Sildenafil was associated with more rigid and longer lasting erections. Additionally, 50 mg of sildenafil was effective in 55% of patients compared to more than 70% of the patients on vardenafil and tadalafil requiring 20 mg for a similar response. Men who used tadalafil were able to achieve erections 24 hours after administration, improving overall satisfaction related to the possible spontaneity of sexual encounters. Del Popolo also evaluated the time/duration effectiveness of PDE5i sildenafil 50 mg versus tadalafil 10 mg (64). Tadalafil 10 mg significantly increased the percentage of successful intercourse attempts at 12–24 hours compared with sildenafil. One can suspect that vardenafil, which has a longer half-life than sildenafil, could offer a similar benefit but a study investigating this occurrence has yet to be performed.
It is normal for a man to have five to six erections during sleep, especially during rapid eye movement (REM). Their absence may indicate a problem with nerve function or blood supply in the penis. There are two methods for measuring changes in penile rigidity and circumference during nocturnal erection: snap gauge and strain gauge. A significant proportion of men who have no sexual dysfunction nonetheless do not have regular nocturnal erections.
The following products are considered to be alternative treatments or natural remedies for Erectile Dysfunction. Their efficacy may not have been scientifically tested to the same degree as the drugs listed in the table above. However there may be historical, cultural or anecdotal evidence linking their use to the treatment of Erectile Dysfunction.

Alprostadil is an FDA-approved erectile dysfunction drug that can be injected directly into the penis to trigger an automatic erection. "Penile injection is the most effective type of ED treatment for men who can't take oral treatment," says Nelson Bennett, MD, a urologist at the Lahey Clinic in Burlington, Mass. In fact, it has an 85 percent success rate. Possible side effects include a burning sensation and priapism, an erection that lasts more than four hours and requires medical treatment.

In 1983, Brindley injected the corpora of several SCI men with phentolamine (85). Two out of the three men had a sufficient erection produced. Since then multiple reports on the efficacy of intracavernosal therapy have been published using, phentolamine, papaverine, prostaglandin, vasoactive intestinal peptide (VIP), and these medications in combination (86-90). These medications have been found to be extremely effective for neurogenic ED due to their ability act locally and essentially bypassing neuronal pathways. Local therapies are usually considered second-line after PDE5i fail to elicit a desired response which can occur in about 25–30% of men with ED, in general (91). Furthermore, the locally delivered medications can be quite dangerous if not used appropriately as priapism and significant pain with injections can occur. These specific occurrences have been suggested as a reason for high discontinuation rates with intracavernosal therapy (92).
While pills for ED are convenient, some men sustain stronger erections by injecting medication directly into the penis. Drugs approved for this purpose work by widening the blood vessels, causing the penis to become engorged with blood. Another option is inserting a medicated pellet into the urethra. The pellet can trigger an erection within 10 minutes.
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