Another study compared the response of surgically and medically castrated rabbits to vardenafil with that of control rabbits. [22] Castrated rabbits did not respond to vardenafil, whereas noncastrated rabbits did respond appropriately. This result suggests that a minimum amount of testosterone is necessary for PDE5 inhibitors to produce an erection.
Many factors can contribute to sexual dysfunction in older men, including physical and psychological conditions, comorbidities and the medications used to treat them. Aspects of an ageing man’s lifestyle and behaviour and androgen deficiency, most often decreasing testosterone levels, may affect sexual function as well. A study of men between the ages of 30 and 79 years showed that 24% had testosterone levels below 300 ng/dL and 5.6% had symptomatic androgen deficiency.2

Adverse effects related to PDE5i use with mild-moderate and transient (58). Furthermore, side effects usually attenuate if use is not discontinued. Autonomic dysreflexia, a life-threatening phenomenon characterized by bradycardia, hypertension, facial flushing and headaches associated with SCI lesions above T6, has not been reported with use. However, hypotension leading to dizziness in individuals treated with sildenafil has been noted with high thoracic and cervical levels of injury (72). No adverse events were noted within the study; however, the dizziness was reported by use of sildenafil 50 mg in the cervical LOI and 100 mg in the thoracic LOI patients. Headache is the most reported side effect of all PDE5i, followed by dyspepsia and flushing. Priapism, and death have not been reported after use of PDE5i by SCI patients.

These oral medications reversibly inhibit penile-specific PDE5 and enhance the nitric oxide–cGMP pathways of cavernous smooth muscle relaxation; that is, all prevent the breakdown of cGMP by PDE5. It is important to emphasize to patients that these drugs augment the body’s natural erectile mechanisms, therefore the neural and psychoemotional stimuli typically needed for arousal still need to be activated for the drugs to be efficacious.
Other factors leading to erectile dysfunction are diabetes mellitus, which is a well-known cause of neuropathy).[2] ED is also related to generally poor physical health, poor dietary habits, obesity, and most specifically cardiovascular disease, such as coronary artery disease and peripheral vascular disease.[2] Screening for cardiovascular risk factors, such as smoking, dyslipidemia, hypertension, and alcoholism is helpful.[2]
Erectile dysfunction (ED) related to compromise of the nervous system is an increasingly common occurrence. This may be due to the multifactorial nature of ED, the myriad of disorders affecting the neurotransmission of erectogenic signals, and improved awareness and diagnosis of ED. Nevertheless, neurogenic ED remains poorly understood and characterized. Disease related factors such as depression, decreased physical and mental function, the burden of chronic illness, and loss of independence may preclude sexual intimacy and lead to ED as well. The amount of data regarding treatment options in subpopulations of differing neurologic disorders remains scarce except for men with spinal cord injury. The treatment options including phosphodiesterase inhibitors, intracavernosal or intraurethral vasoactive agents, vacuum erection devices (VED) and penile prosthetic implantation remain constant. This review discusses the options in specific neurologic conditions, and briefly provides insight into new and future developments that may reshape the management of neurogenic ED.
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.
Erectile dysfunction may be the result of arterial and non-arteritic causes. Hardening of the arteries that bring blood into the penis, atherosclerosis, is a common cause of erectile dysfunction, particularly in men with cardiovascular disease. However, problems with the nerves that supply the penis as well as the veins that drain blood out of the penis can also cause troubles with erection. Erectile dysfunction may also have a psychological cause.
Injection therapy involves injecting a substance into the penis to enhance blood flow and cause an erection. The Food and Drug Administration (FDA) approved a drug called alprostadil (Caverject) for this purpose in July of 1995. Alprostadil relaxes smooth muscle tissue to enhance blood flow into the penis. It must be injected shortly before intercourse. Another, similar drug that is sometimes used is papaverine—not yet been approved by the FDA for this use. Either drug may sometimes cause painful erections or priapism (uncomfortable, prolonged erections) that must be treated with a shot of epinephrine.
Begot, I., Peixoto, T. C. A., Gonzaga, L. R. A., Bolzan, D. W., Papa, V., Carvalho, A. C. C., ... & Guizilini, S. (2015, March 1). A Home-Based Walking Program Improves Erectile Dysfunction in Men With an Acute Myocardial Infarction. The American Journal of Cardiology, 115(5), 5741-575. Retrieved from http://www.ajconline.org/article/S0002-9149(14)02270-X/abstract
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).
When it comes to boosting sexual performance, many men will walk all over God’s green earth looking for ways to maintain a good sex life. Luckily men, all you have to do is walk — not run — 2 miles a day. This, along with other healthier lifestyle interventions can help obese men reduce their risk of ED, or even “reverse” current impotence, according to a 2005 study. This comes of importance, since maintaining a trim waistline is a good defense for ED, as men with a 42-inch waist are 50 percent more likely to have ED than those with a 32-inch waist. Getting to a healthy weight and maintaining it is a good strategy for preventing and treating ED.
As is true in so many medical conditions, lifestyle modifications, considered first-line therapy, can have a salutary effect in ED management, and men should be encouraged to make the necessary changes to the benefit of their sexual function and to their overall health as well. Despite the benefits of behaviour modification, men presenting with ED want the physician to help with measures that can have an immediate impact.
The somatosensory pathways for erections originate in the penile skin, glans and urethra. Glans afferent sensory free nerve endings are 10-fold more than their corpuscular receptors, and are derived from Aδ and unmyelinated C fibers. The nerve endings coalesce to form the dorsal penile nerve along with other sensory nerve fibers. Through the pudendal nerve they enter the S2-4 nerve roots to terminate on spinal neurons and interneurons. The dorsal nerve is not purely somatic, however. Nerve bundles within the dorsal nerve contain nitric oxide (NO) synthase, found typically in autonomic nerves, and stimulation of the sympathetic chain can leak to evoked potentials from the dorsal nerve and vice versa (10-12).
Since the advent of PDE5i, many other selective and non-selective peripheral acting compounds have been developed or are in development. Avanafil has shown promising results in treating ED in post-prostatectomy patients with suspected cavernous nerve injury (111). Other PDE5i marked in Asia such as udenafil, and mirodenafil also effective at treating ED may minimize side effects due to shorter half-lives (112-114). Soluable guanylate-cyclase inhibitors and potassium channel activators are compounds that have induced erections in animal models but remain experimental requiring further investigation (115-117).
ED can also occur among younger men. A 2013 study found that one in four men seeking their first treatment for ED were under the age of 40. The researchers found a stronger correlation between smoking and illicit drug use and ED in men under 40 than among older men. That suggests that lifestyle choices may be a main contributing factor for ED in younger men.
In one study, 9.6% reported ‘occasional’ erectile dysfunction, 8.9% reported erectile dysfunction occurring ‘often’, and 18.6% reported erectile dysfunction occurring ‘all the time’. Of these, only 11.6% had received treatment.In another study, only 14.1% of men reported that they had received treatment, despite experiencing erectile dysfunction for longer than 12 months.
A study published in May 2014 in The Journal of Sexual Medicine found that some men can reverse erectile dysfunction with healthy lifestyle changes, such as exercise, weight loss, a varied diet, and good sleep. The Australian researchers also showed that even if erectile dysfunction medication is required, it's likely to be more effective if you implement these healthy lifestyle changes.
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).

Stress is your body responding to your environment. And it’s a good thing—in limited doses. When you get stressed out your body makes chemicals like adrenaline that make you stronger, faster, fitter, and even able to think more clearly. Most people call this reaction the “fight-or-flight” response, and it’s a life-saver in dangerous situations. In a very real sense, adrenaline makes you a part-time superhero. The problems happen when your body deals with constant stress.
This is one of many types of constricting devices placed at the base of the penis to diminish venous outflow and improve the quality and duration of the erection. This is particularly useful in men who have a venous leak and are only able to obtain partial erections that they are unable to maintain. These constricting devices may be used in conjunction with oral agents, injection therapy, and vacuum devices.
Psychosexual counselling, or sex therapy, is an appropriate recommendation especially for men who are experiencing discord with their partner especially if the conflict is related to the man’s ED. Counselling usually consists of 5–20 sessions with counsellor. It is our recommendation that referral doctors treating men with ED make a referral to a psychotherapist or sex therapist who is certified by AASECT (American Association of Sexuality Educators, Counselors and Therapists) of certified sexuality educator.43
Alteration of NO levels is the focus of several approaches to the treatment of ED. Inhibitors of phosphodiesterase, which primarily hydrolyze cGMP type 5, provided the basis for the development of the PDE5 inhibitors. Chen et al administered oral L-arginine and reported subjective improvement in 50 men with ED. [14] These supplements are readily available commercially. Reported adverse effects include nausea, diarrhea, headache, flushing, numbness, and hypotension.
All NOS subtypes produce NO, but each may play a different biologic role in various tissues. nNOS and eNOS are considered constitutive forms because they share biochemical features: They are calcium-dependent, they require calmodulin and reduced nicotinamide adenine dinucleotide phosphate for catalytic activity, and they are competitively inhibited by arginine derivatives. nNOS is involved in the regulation of neurotransmission, and eNOS is involved in the regulation of blood flow.
The Latin term impotentia coeundi describes simple inability to insert the penis into the vagina; it is now mostly replaced by more precise terms, such as erectile dysfunction (ED). The study of ED within medicine is covered by andrology, a sub-field within urology. Research indicates that ED is common, and it is suggested that approximately 40% of males experience symptoms compatible with ED, at least occasionally.[38] The condition is also on occasion called phallic impotence.[39] Its antonym, or opposite condition, is priapism.[40][41]
There are so many potential reasons a man might develop erectile dysfunction (ED), it's nearly impossible to generalize the best ways to treat it. What works for one man may not work for another simply because they are having problems for different reasons. That said, it may encouraging to hear that there are a variety of options that may be considered, from psychological counseling to lifestyle changes, medications to treatments and devices.
In fact, one common reason many younger men visit their doctor is to get erectile dysfunction medication. Often, men with erectile dysfunction suffer with diabetes or heart disease, or may be sedentary or obese, but they don’t realize the impact of these health conditions on sexual function. Along with erectile dysfunction treatment, the doctor may recommend managing the illness, being more physically active, or losing weight.

The Prostate Cancer Prevention Trial was a landmark study by Thompson et al that prospectively assessed the time to developing CVD after the diagnosis of ED. There were 4247 men with no ED at study entry; 2420 developed incident ED (defined as the first report of ED of any grade) over 5 years. Those men that developed ED had a 1.45-fold higher probability of experiencing a CV event compared with men who did not develop ED.27

If it is determined that ED is a problem, the patient evaluation should include a detailed sexual and medical history and a physical exam. In particular, it is important to evaluate the ED within the context of ejaculatory problems. There is a strong interplay between premature ejaculation (PE) and ED, with about a third of ED patients reporting PE. The relationship between the PE and ED is bidirectional and successful treatment of one often requires treatment of the other.14
This is one of many types of constricting devices placed at the base of the penis to diminish venous outflow and improve the quality and duration of the erection. This is particularly useful in men who have a venous leak and are only able to obtain partial erections that they are unable to maintain. These constricting devices may be used in conjunction with oral agents, injection therapy, and vacuum devices.
Research has even found possible links to frequent ejaculation and a lower risk of prostate cancer. In one study of 32,000 men published in 2016 in the journal European Urology, for example, men who ejaculated at least 21 times per month while in their 20s were less likely to be diagnosed with prostate cancer than those who ejaculated four to seven times per month. And men who ejaculated more often in their 40s were 22 percent less likely to get a prostate cancer diagnosis.
Herbal supplements such as ginkgo biloba, saw palmetto, and yohimbe have been touted as sexual enhancers, and some men have been tempted to try them to treat erectile dysfunction. Bennett warns, however, that none has been approved by the FDA or even shown by any reliable studies to prevent, treat, or improve erectile dysfunction. Moreover, supplements are unregulated and can have many side effects or interfere with prescribed medications you’re already taking. Don’t jeopardize your health by taking a supplement to treat erectile dysfunction without first talking with your doctor.
The medications are extremely effective, which is very good. And the medications are, for the most part, extremely well-tolerated. But there are, like with any medications, a potential downside. The one absolute downside to the use of any of these erection what we call PDE5 medications is if a patient is using a nitroglycerin medication. And nitroglycerins are used for heart disease and for angina, for the most part, although there are some recreational uses of nitrites. And that’s important because your blood vessels will dilate and your blood pressure will drop. And that is an absolute contraindication.
Nearly every primary care physician, internist and geriatrician now understand that many older men retain an interest in sexual activity as they age. Some primary care physicians think that sexual potency in older men is the norm, and that if it is lacking, it is ‘all in the head.’ This viewpoint has not been supported by current literature. The Massachusetts Male Aging Study (MMAS) found that 52% of men between 40 and 70 years old reported having some form of erectile dysfunction (ED).1 The reality is that ED is a natural part of ageing and that the prevalence increases with age. In the MMAS, they found that roughly 50% of men at 50 years old, 60% of men at 60 years old and 70% of men at 70 years old had ED. Thus, nearly all men who live long enough should develop ED. The myths that surround the problems of impotence or ED confound the attempts of patients to receive treatment and the attempts of physicians to help them.1
A variety of personal habits and lifestyle choices have been linked to ED. In some ways, this is a good thing, since habits can be broken and choices reconsidered. What's more, many of the lifestyle factors that contribute to sexual problems are ones that affect overall health and well-being, both physical and mental. Addressing these factors, therefore, can have benefits beyond improving erectile dysfunction.
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.
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