Erections are neurovascular events, meaning that nerves and blood vessels (arteries and veins) are involved in the process of an erection and all must work properly to develop a hard erection that lasts long enough. Erection begins with sexual stimulation. Sexual stimulation can be tactile (for example, by a partner touching the penis or by masturbation) or mental (for example, by having sexual fantasies, viewing porn). Sexual stimulation or sexual arousal causes the nerves going to the penis to release a chemical, nitric oxide. Nitric oxide increases the production of another chemical, cyclic GMP (cGMP), in the muscle of the corpora cavernosa. The cGMP causes the muscles of the corpora cavernosa to relax, and this allows more blood to flow into the penis. The incoming blood fills the corpora cavernosa, making the penis expand.
Some men should not take PDE5 inhibitors. They can cause hypotension (abnormally low blood pressure that can lead to fainting and even shock) when given to patients who are taking nitrates (medications taken for heart disease). Therefore, patients taking nitrates daily should not take any of the PDE5 inhibitors. Nitrates relieve angina (chest pain due to insufficient blood supply to the heart muscle because of narrowing of the coronary arteries); these include nitroglycerine tablets, patches, ointments, sprays, and pastes, as well as isosorbide dinitrate and isosorbide mononitrate. Other nitrates such as amyl nitrate and butyl nitrate also are in some recreational drugs called "poppers."
If you are taking medications (alpha-blockers) for problems with an enlarged prostate, you should discuss your prostate medications with your doctor. Alpha-blockers also can cause lowering of the blood pressure. Thus your doctor will need to carefully watch your blood pressure when you start the PDE5 inhibitor. Common alpha-blockers include doxazosin (Cardura), terazosin (Hytrin), and tamsulosin (Flomax).
As blood flows into the penis, the corpora cavernosa swell, and this swelling compresses the veins (blood vessels that drain the blood out of the penis) against the tunica albuginea. Compression of the veins prevents blood from leaving the penis. This creates a hard erection. When the amount of cGMP decreases by the action of a chemical called phosphodiesterase type 5 (PDE5), the muscles in the penis tighten, and the blood flow into the penis decreases. With less blood coming into the penis, the veins are not compressed, allowing blood to drain out of the penis, and the erection goes down.

Surgery to repair arteries (penile arterial reconstructive surgery) can reduce impotence caused by obstructions that block the flow of blood to the penis. The best candidates for such surgery are young men with discrete blockage of an artery because of a physical injury to the pubic area or a fracture of the pelvis. The procedure is less successful in older men with widespread blockage of arteries.

Think of erectile dysfunction as your body’s “check engine light.” The blood vessels in the penis are smaller than other parts of the body, so underlying conditions like blocked arteries, heart disease, or high blood pressure usually show up as ED before something more serious like a heart attack or stroke. ED is your body’s way of saying, “Something is wrong.” And the list of things that cause erectile dysfunction can include:
Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus.
Penis pumps produce erections by drawing blood, via air suction, into the penis. The devices consist of a cylindrical tube, 12 to 18 inches long, connected by a small air hose to a hand pump (on many models this resembles the squeeze mechanism on a blood pressure monitor). Users place the tube over the penis then pump to produce an erection. They must then place an elastic band around the base of the penis to keep the blood there and maintain the erection.  
Both ED and low testosterone (hypogonadism) increase with age. The incidence of the latter is 40% in men aged 45 years and older. [15] 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). [16]
In patients with low testosterone, testosterone treatment can improve libido and erectile dysfunction, but many men still may need additional oral medications such as sildenafil, vardenafil, or tadalafil. Some studies suggest that men with ED and low testosterone may respond better to PDE5 inhibitors when given testosterone therapy; however, this is controversial.
Of the drugs used for depression, tricyclic antidepressants may be associated with erectile problems and other drugs may be substituted to prevent this complication. Currently available substitutes include bupropion, nefazodone, and trazodone. The selective serotonin reuptake inhibitors (eg, fluoxetine, sertraline, paroxetine, citalopram) can also cause difficulties with ED, but they might also have other significant sexual side effects, including decreased libido and anorgasmia.
Finally, gene therapy and stem cell research has widened the frontier of ED treatment proposed as possibility to even reverse ED. Specifically, gene therapy pertains to repairing the cause of ED by restoring defective gene function and/or altering the expression of the mutant gene (32). Most of the available data on gene therapy are in the animal model. However, a phase I clinical trial in men with ED undergoing intracavernous injection with a DNA plasmid carrying the alpha-subunit of the corporal smooth muscle Maxi-K channel showed promise in increased erectile function based on IIEF assessment sustained throughout the 3-month study period (122).
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!
One study by Palmer and colleagues evaluated sildenafil use in SB males with thoracic lesions (76). A prospective, blinded, randomized, placebo-controlled, dose-escalation, crossover study in 17 patients with SB and ED was performed. All study participates took sets of tablet in groups, two sets of placebo, one of 25 mg, and the last 50 mg. Overall response to the tablet sets was measured by IIEF response and self-report of erectile rigidity. Patients reported that taking 50 mg of sildenafil led to improved erections, duration of erections, frequency of erections and level of confidence compared to sildenafil 25 mg and more significantly compared to placebo. Of the five patients who reported side effects, two experienced mild hematological changes that reverted to baseline after study completion.

Some men should not take PDE5 inhibitors. They can cause hypotension (abnormally low blood pressure that can lead to fainting and even shock) when given to patients who are taking nitrates (medications taken for heart disease). Therefore, patients taking nitrates daily should not take any of the PDE5 inhibitors. Nitrates relieve angina (chest pain due to insufficient blood supply to the heart muscle because of narrowing of the coronary arteries); these include nitroglycerine tablets, patches, ointments, sprays, and pastes, as well as isosorbide dinitrate and isosorbide mononitrate. Other nitrates such as amyl nitrate and butyl nitrate also are in some recreational drugs called "poppers."
Tests such as the bulbocavernosus reflex test are used to determine if there is sufficient nerve sensation in the penis. The physician squeezes the glans (head) of the penis, which immediately causes the anus to contract if nerve function is normal. A physician measures the latency between squeeze and contraction by observing the anal sphincter or by feeling it with a gloved finger inserted past the anus.
The first line and by far the most common treatment today is with the prescription drug sildenafil citrate, sold under the brand name Viagra. An estimated 20 million prescriptions for the pill have been filled since it was approved by the FDA in March 1998. It is also the most effective treatment with a success rate of more than 60%. The drug boosts levels of a substance called cyclic GMP, which is responsible for widening the blood vessels of the penis. In clinical studies, Viagra produced headaches in 16% of men who took it, and other side effects included flushing, indigestion, and stuffy nose.
Uses and risks of viagra Viagra treats erectile dysfunction and pulmonary arterial hypertension. For sexual purposes, it helps someone with erectile dysfunction achieve and maintain an erection. However, Viagra can have unpleasant side effects, and an overdose can be serious. We cover everything you need to know about Viagra in this article. Read now
In a prospective, multicenter, single-armed study of ED patients who exhibited a suboptimal response to PDE5 inhibitors, the investigators found that percutaneous implantation of zotarolimus-eluting stents in focal atherosclerotic lesions was both safe and feasible and was associated with clinically meaningful improvement on subjective and objective measures of erectile function. [3]
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
All studies demonstrate a strong association with age, even when data are adjusted for the confounding effects of other risk factors. The independent association with aging suggests that vascular changes in the arteries and sinusoids of the corpora cavernosa, similar to those found elsewhere in the body, are contributing factors. Other risk factors associated with aging include depression, sleep apnea, and low HDL levels.
There are many effective treatments for impotence. The most popular is a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. These include sildenafil (Viagra), vardenafil (Levitra), tadalafil (Cialis) and avanafil (STENDRA). These drugs are taken in pill form. They work in most men. But they are less effective in men with neurological causes of impotence.

And surgery comes with its own serious risks, such as developing incontinence or impotence, while radiation can result in urinary problems. — Peter Loftus, WSJ, "Surgery Adds Three Years to Lives of Prostate-Cancer Patients, Study Finds," 12 Dec. 2018 Male-impotence pill Viagra began facing generic competition late last year, while the Lyrica pain treatment is expected to confront generics at the end of this year. — Jonathan D. Rockoff, WSJ, "Pfizer Narrows Guidance on Tougher Pricing, Generic Competition," 30 Oct. 2018 Arkham Horror Third Edition is a classic struggle of agency versus impotence, set in the uncanny world of H.P. Lovecraft’s Cthulhu mythos. — Charlie Theel, Ars Technica, "Arkham Horror Third Edition: The classic Lovecraft adventure returns," 24 Nov. 2018 There’s obviously a lot of anger and frustration here toward the US government at the moment—along with side effects like bottled rage and sometimes a creeping sense of ineptitude or impotence about our ability to do anything about it. — Corey Seymour, Vogue, "Pussy Riot's Nadya Tolokonnikova On Her New Guide To Activism, Raising The Next President Of Russia, And Her "Holy War" On Fairy Tales," 12 Oct. 2018 In exchange for political impotence, they would be mostly left alone and allowed to get rich. — Paul Mozur, New York Times, "Inside China’s Dystopian Dreams: A.I., Shame and Lots of Cameras," 8 July 2018 Their suspicion is compounded by rumors that the polio vaccine causes impotence, death and, ironically, paralysis. — Meher Ahmad, New York Times, "Pakistan Has Just One New Polio Case, but Isn’t Declaring Victory Yet," 20 May 2018 Fighting back, even as an exercise in impotence, did a lot for McCain. — Alex Horton, Washington Post, "John McCain rebelled at the Naval Academy — and as a POW — long before he was a Senate maverick," 3 May 2018 Feelings of desperation and impotence are being felt throughout Central America, where the lawlessness, endemic poverty and levels of gang violence akin to war zones that have driven so many families from their homes show little signs of abating. — Washington Post, "Violence keeps Central Americans coming to US despite Trump," 21 June 2018
A physical cause can be identified in about 80% of cases.[2] These include cardiovascular disease, diabetes mellitus, neurological problems such as following prostatectomy, hypogonadism, and drug side effects. Psychological impotence is where erection or penetration fails due to thoughts or feelings; this is somewhat less frequent, in the order of about 10% of cases.[2] In psychological impotence, there is a strong response to placebo treatment.
"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.
In comparison, 37% of men who had received external radiotherapy as their primary therapy reported the ability to attain functional erections suitable for intercourse, along with 43% of men who had received brachytherapy as primary treatment. Pretreatment sexual health-related quality of life score, age, serum prostate-specific antigen (PSA) level, race or ethnicity, body mass index, and intended treatment details were associated with functional erections 2 years after treatment. [45]
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.
What happens is that the blood vessels of the penis are rather small, and a small amount of plaque in the penile arteries is going to result in erectile dysfunction. You need more plaque before the person’s actually symptomatic from a heart problem, but they’re linked. And so when anybody, any man has an erectile issue, it’s incumbent upon the physician to make certain that their cardiac status is healthy.
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