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.
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.
Erections are initiated and maintained via integration of afferent inputs in the supra sacral regions of the central nervous system. Regions of the brain cited to have key roles in the integration of signals include the medial amygdala, MPOA, periaqueductal gray matter, paraventricular nucleus (PVN), and ventral tegmentum among others (16). Studies in animal models, particularly in rats, have been paramount in identifying these key areas of signal integration and control. Electrostimulation of the MPOA, PVN and hippocampus lead to erection and lesions in these areas may prevent erection (17). Marson et al. injected labeled pseudorabies virus into rat corpora cavernosa and traced them to neurons in the spinal cord, brain stem and hypothalamus (18). Stimulation of the rat dorsal nerve led to increased firing in the MPOA not found elsewhere (19). Axonal tracing in animals have shows direct projections from the hypothalamus to the lumbosacral autonomic erection centers. Oxytocin and vasopressin have been identified as central neurotransmitters within the hypothalamic nuclei and may have a role in penile erection (17). These signaling studies identifying key areas of erectile response integration may explain how ED is associated with cerebrovascular accident (CVA), Parkinson’s, epilepsy and MS.
Impotence, or erectile dysfunction, is the inability of a male to attain and keep an erection sufficiently firm to engage in or complete sexual intercourse. Although it is more common in older men, impotence can occur at any age. Impotence is not a normal consequence of aging. About 70% of erectile dysfunction is due to diseases such as diabetes and atherosclerosis, another 10% to 20% is due to psychological factors, and the remaining percentage is related to medications, lifestyle factors, and injury (Source: NIDDK).
The physical examination can reveal clues for physical causes of erectile dysfunction. A doctor will perform an assessment of BMI and waist circumference to evaluate for abdominal obesity. A genital examination is part of the evaluation of erectile dysfunction. The examination will focus on the penis and testes. The doctor will ask you about penile curvature and will examine the penis to see if there are any plaques (hard areas) palpable. The doctor will examine the testes to make sure they are in the proper location in the scrotum and are normal in size. Small testicles, lack of facial hair, and enlarged breasts (gynecomastia) can point to hormonal problems such as hypogonadism with low testosterone levels. A health care provider may check pulses in your groin and feet to determine if there is a suggestion of hardening of the arteries that could also affect the arteries to the penis.
SD in MS can be classified into three categories. Primary SD is due directly due to MS-related neurological deficits, secondary SD is related to physical impairments and symptoms or drugs used for MS treatment, and tertiary SD is due to the psychological, social and cultural problems attributed to MS (38). These classifications are important, and underscore the importance of addressing all the issues leading to SD not just the neurologic impairment.
Picture of penile tumescence monitor. This penile tumescence monitor is placed at the base and near the corona of the penis. It is connected to a monitor that records a continuous graph depicting the force and duration of erections that occur during sleep. The monitor is strapped to the leg. The nocturnal penile tumescence (NPT) test is conducted on several nights to obtain an accurate indication of erections that normally occur during the alpha phase of sleep.
Prior to starting with treatment of erectile dysfunction, it is important to make sure that it is safe from a medical standpoint to participate in sexual activity. Sexual activity is physical exertion, and in some men with significant heart disease, this increase in physical exertion can increase the risk of a heart attack. Thus, it is very important to discuss your cardiovascular risks with your doctor prior to trying any medication or treatment for erectile dysfunction.
Sexual dysfunction is highly prevalent in men and women. In the MMAS, 52% of the respondents reported some degree of erectile difficulty. Complete ED, defined as (1) the total inability to obtain or maintain an erection during sexual stimulation and (2) the absence of nocturnal erections, occurred in 10% of the respondents. Mild and moderate ED occurred in 17% and 25% of responders, respectively. 
Commercials for drugs to improve “low T,” or testosterone, the male hormone, are now vying for airtime, but they address desire, not performance. "Male hormone is not an approved treatment for erectile dysfunction," notes Bennett. "It may be used to increase desire in men who have low testosterone, but it doesn’t improve blood flow to an erection." A doctor can do a blood test to check you for low testosterone, but it is a rare cause of ED. Hormone therapy with injections, patches, or gels applied to the skin may improve mood and sex drive, but it likely won’t fix any mechanical issues. Also, testosterone drugs should not be used by men with prostate cancer. Side effects include acne, breast enlargement, prostate enlargement, and fluid retention.
The first stem cell study for the treatment of ED was published in 2004. This study used embryonic stem cells to treat ED. At this time, there is a total of 36 published basic studies assessing stem cell therapy for ED, with two clinical trials. The mechanism of action of stem cells is to generate angiogenesis with subsequent increase in cavernosal smooth muscle cells within the corporal bodies.46
Experts often treat psychologically based impotence using techniques that decrease anxiety associated with intercourse. The patient's partner can help apply the techniques, which include gradual development of intimacy and stimulation. Such techniques also can help relieve anxiety during treatment of physical impotence. If these simple behavioral methods at home are ineffective, a doctor may refer an individual to a sex counselor.
Sildenafil is available as oral tablets at doses of 25 mg, 50 mg, and 100 mg. Patients should take sildenafil approximately one hour before sexual activity. In some men, the onset of action of the drug may be as early as 11-20 minutes. It's best for men to take sildenafil on an empty stomach for best results since absorption and effectiveness of sildenafil can be diminished if it is taken shortly after a meal, particularly a meal that is high in fat. Sildenafil and the other PDE5 inhibitors don't cause an immediate erection. Sexual stimulation is necessary for these medications to work.
Patients with both ED and cardiovascular disease who receive treatment with an oral PDE5 inhibitor require education regarding what to do if anginal episodes develop while the drug is in their system. Such education includes stressing the importance of alerting emergency care providers to the presence of the drug so that nitrate treatment is avoided.
Other medical therapies under evaluation include ROCK inhibitors and soluble guanyl cyclase activators. Melanocortin receptor agonists are a new set of medications being developed in the field of erectile dysfunction. Their action is on the nervous system rather than the vascular system. PT-141 is a nasal preparation that appears to be effective alone or in combination with PDE5 inhibitors. The main side effects include flushing and nausea. These drugs are currently not approved for commercial use.
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.
Prior to the introduction of PDE5i in 1998, intracavernosal vasoactive medications and penile implant surgery were the mainstays of treatment. Penile implant surgery involves placement of inflatable or malleable rods within the corpora cavernosa to provide rigidity for intercourse. Choice of which implant to place usually depends upon manual dexterity and function of the patient, patient anatomy, physician preference and surgical approach.
Exercise and lifestyle modifications may improve erectile function. Weight loss may help by decreasing inflammation, increasing testosterone, and improving self-esteem. Patients should be educated to increase activity, reduce weight, and stop smoking, as these efforts can improve or restore erectile function in men without comorbidities. Precise glycemic control in diabetic patients and pharmacologic treatment of hypertension may be important in preventing or reducing sexual dysfunction. 
Having erection trouble from time to time isn't necessarily a cause for concern. If erectile dysfunction is an ongoing issue, however, it can cause stress, affect your self-confidence and contribute to relationship problems. Problems getting or keeping an erection can also be a sign of an underlying health condition that needs treatment and a risk factor for heart disease.