Erectile dysfunction - (ED) or impotence is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual activity. A penile erection is the hydraulic effect of blood entering and being retained in sponge-like bodies within the penis. The process is most often initiated as a result of sexual arousal, when signals are transmitted from the brain to nerves in the penis.
Instead of the hesitation with which he had accosted the cardinal a quarter of an hour before, there might be read in the eyes of the young king that will against which a struggle might be maintained, and which might be crushed by its own impotence, but which, at least, would preserve, like a wound in the depth of the heart, the remembrance of its defeat.
In prescribing sildenafil, a doctor considers the age, general health status, and other medication(s) the patient is taking. The usual starting dose for most men is 50 mg, however, the doctor may increase or decrease the dose depending on side effects and effectiveness. The maximum recommended dose is 100 mg every 24 hours. However, many men will need 100 mg of sildenafil for optimal effectiveness, and some doctors are recommending 100 mg as the starting dose.
Talk with your doctor before trying supplements for ED. They can contain 10 or more ingredients and may complicate other health conditions. Asian ginseng and ginkgo biloba (seen here) are popular, but there isn't a lot of good research on their effectiveness. Some men find that taking a DHEA supplement improves their ability to have an erection. Unfortunately, the long-term safety of DHEA supplements is unknown. Most doctors do not recommend using it.
Men with medical conditions that may cause a sustained erection, such as sickle cell anemia, leukemia, or multiple myeloma, or a man who has an abnormally-shaped penis, may not benefit from these medications. Also, men with liver diseases or a disease of the retina, such as macular degeneration or retinitis pigmentosa, may not be able to take these medications, or may need to take the lowest dosage.
The link between chronic disease and ED is most striking for diabetes. Men who have diabetes are two to three times more likely to have erectile dysfunction than men who do not have diabetes. Among men with erectile dysfunction, those with diabetes may experience the problem as much as 10 to 15 years earlier than men without diabetes. Yet evidence shows that good blood sugar control can minimize this risk. Other conditions that may cause ED include cardiovascular disease, atherosclerosis (hardening of the arteries), kidney disease, and multiple sclerosis. These illnesses can impair blood flow or nerve impulses throughout the body.
Diabetes is a well-recognized risk factor for ED. A systematic review and meta-analysis found that the prevalence of ED was 37.5% in type 1 diabetes, 66.3% in type 2 diabetes, and 52.5% in diabetes overall—a rate approximately 3.5 times higher than that in controls.  The etiology of ED in diabetic men probably involves both vascular and neurogenic mechanisms. Evidence indicates that establishing good glycemic control can minimize this risk.
Surgery: If neither drugs nor the vacuum pump works, your doctor may suggest surgery. With surgery, the doctor can place a device in your penis that will cause enough hardness for intercourse. In a few cases, infections may develop after the operation, and the doctor may have to remove the device. Another operation that may help you is rebuilding the blood vessels in the penis to increase blood flow into the penis or decrease blood flow out of the penis. These procedures can help you to get and maintain an erection.
Trauma to the pelvic blood vessels or nerves can also lead result in ED. Bicycle riding for long periods has been implicated as an etiologic factor; direct compression of the perineum by the bicycle seat may cause vascular and nerve injury.  On the other hand, bicycling for less than 3 hours per week may be somewhat protective against ED.  Some of the newer bicycle seats have been designed to diminish pressure on the perineum. [37, 38]
The next new treatments for erectile dysfunction will probably be improvements in some ED drugs already being used. "A dissolvable form of Levitra that you put under your tongue is coming that may work more quickly than the pills we have now," says Feloney. A new form of alprostadil may make it possible for you to rub it directly on the penis instead of inserting or injecting it. And newer phosphodiesterase inhibitors that last even longer and cause fewer side effects are being developed. Stay tuned!
Cosgrove et al reported a higher rate of sexual dysfunction in veterans with posttraumatic stress disorder (PTSD) than in veterans who did not develop this problem.  The domains on the International Index of Erectile Function (IIEF) questionnaire that demonstrated the most change included overall sexual satisfaction and erectile function. [43, 44] Men with PTSD should be evaluated and treated if they have sexual dysfunction.
"For men who are unwilling or unable to self-inject alprostadil, the FDA has approved this dissolvable pellet that can be inserted directly into the urethra, the opening of the penis," says Dr. Feloney. MUSE, with an inspiring name that actually stands for medicated urethral system for erection, will trigger an erection in about 10 minutes that may last as long as an hour. Using MUSE to treat ED can result in somewhat unpleasant side effects, however — including an aching sensation, burning, redness, and minor bleeding.
Erythrocytosis has been noted in men on TRT, and should be monitored every 6–12 months depending upon the patients’ response to changes in haematocrit levels. For mild elevations, the dosage of testosterone can be decreased or the interval of using the medication can be increased. With the haematocrit greater than 50%, decisions to temporarily discontinue the medication or periodic phlebotomy may be indicated.38
Alprostadil may also be administered into the urethral opening of the penis. In MUSE (medical urethral system for erection), the man inserts a thin tube the width of a vermicelli noodle into his urethral opening and presses down on a plunger to deliver a tiny pellet containing alprostadil into his penis. The drug takes about 10 minutes to work and the erection lasts about an hour. The main side effect is a sensation of pain and burning in the urethra, which can last about five to 15 minutes.
Patient can inject medications directly into the corpora cavernosa to help attain and maintain erections. Medications such as papaverine hydrochloride, phentolamine, and prostaglandin E1 (alprostadil) can be used alone or in combinations to attain erections. All of these medications are vasodilators and work by increasing blood flow into the penis. Prostaglandin E1 (Caverject, Edex) is easier to obtain; however, it is associated with penile pain in some individuals. The use of combinations of two or three of these medications can decrease the risk of having penile pain.
Induction of erection occurs after stimulation of the cavernous and pelvic nerve plexus. Conversely, stimulation of the sympathetic trunk leads to detumescence. The reflex erectile response requires that the sacral reflex arc remain intact. Tactile and sensory signals are received by the somatic sensory pathways and integrate with parasympathetic nuclei within the sacral spinal cord (S2-4) leading to induction of erection via cholinergic signaling. These reflexogenic erections remain intact with upper motor neuron injuries. Psychogenic erections do not require that the sacral reflex arc remain intact. In a cat models, spinal cord removal below L4/L5 led to absence of a reflexogenic erection but stimulation of the medial preoptic area (MPOA) or placement near a female cat in heat led to erection (5,6). Psychogenic erections occur via induction of central pathways traveling from the brain through the sympathetic chain. Non-penile sensory pathways induced by sight, sound, touch and smell travel through the MPOA to the erection centers within the cord T11-L2, and S2-S4 to induce erections (7). When a sacral lower motor neuron injury is present in men, below T12 these types of erections are more likely to occur (8). Spinal cord lesions above T9 are not associated with psychogenic erections (9). Rigidity of erections is less with psychogenic erections because the thoracolumbar sympathetic outflow may contain a decreased concentration of neurons compared to the parasympathetic outflow from the sacral spinal cord.
There are also alternative treatments, such as using a penis pump or a penile injection. Penis pumps work by creating a vacuum and thereby causing more blood to flow to your penis. Penile injections need to be used shortly before intercourse. They contain a medication which widens your blood vessels. A doctor’s prescription is needed for the injections.
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.
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).
I think that a very powerful argument to young men who want to perform at the highest level is to point out the destructive nature of what they’re doing. If they’re having 18 drinks per week, if they’re having three, four, five drinks at any one time, they’re going to guarantee that their erections are not going to be at the highest level. I can’t tell you the number of men who come in saying, they went out, they had a date, they had a big dinner– which, by the way, is also not a great thing for erections, because all the blood is now going to your gut instead of to the genital area. And how important lifestyle changes are to improving your performance, as well, if not better, than the medications. So make certain that you exercise modestly, not excessively. Make certain that you have a smaller meal on an evening or a day that you want to have a sexual encounter, because you want the blood to go, once again, to the penile area and not to your gut. And really, the whole idea of stress– if you’re stressed out, if you’re worried about a lot of things, if you’re distracted, you can’t initiate that psychic stimulus to your spinal cord and then ultimately to your penis. So stress management is incredibly important.
Implantable penile prostheses are usually considered a last resort for treating impotence. They are implanted in the corpora cavernosa to make the penis rigid without the need for blood flow. The semirigid type of prosthesis consists of a pair of flexible silicone rods that can be bent up or down. This type of device has a low failure rate but, unfortunately, it causes the penis to always be erect, which can be difficult to conceal under clothing.
Both ED and low testosterone (hypogonadism) increase with age. The incidence of the latter is 40% in men aged 45 years and older.  Testosterone is known to be important in mood, cognition, vitality, bone health, and muscle and fat composition. It also plays a key role in sexual dysfunction (eg, low libido, poor erection quality, ejaculatory or orgasmic dysfunction, reduced spontaneous erections, or reduced sexual activity). 
ED is defined as the inability to achieve a full erection or the inability to maintain an erection adequate for sexual intimacy. Other types of sexual dysfunction such as premature ejaculation and low libido may occur; however, the most common and disruptive problem in men is ED. Although most men will experience periodic episodes of ED, these episodes tend to become more frequent with advancing age.
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