Erection is a neurovascular event that involves spinal and supra spinal pathways. The final common pathway involves the release of nitric oxide (NO) from both endothelial cells and neurons, which acts as a vasodilator causing penile engorgement and erection. NO is degraded by the enzyme phosphodiesterase (PDE) type 5 in the penis. Erectile dysfunction (ED), defined as the persistent inability to achieve and/or maintain an erection sufficient for satisfactory sexual performance, results when the neurovascular pathway is interrupted by medical conditions or drugs. A 15-item self-administered questionnaire, the International Index of Erectile Function (IIEF), is one of the most useful tools to evaluate erectile function (EF) in clinical trials, although of much less use in routine clinical practice. The MMAS (Massachusetts Male Aging Study) was the first major epidemiological investigation to study the prevalence of ED. The study found that ED was three times more common in patients with diabetes mellitus. The aetiopathogenesis of ED in diabetes is multifactorial, with vascular and neural factors being equally implicated. Hyperglycaemia is believed to give rise to biochemical perturbations that lead to these microvascular changes. In the MMAS, ED in diabetes was strongly correlated with glycaemic control, duration of disease and diabetic complications. The incidence increased with increasing age, duration of diabetes and deteriorating metabolic control, and was higher in individuals with type 2 diabetes than those with type 1.ED in men with diabetes often affects their quality of life and, as patients are often reluctant to come forward with their symptoms, a carefully taken history is one of the most useful approaches in identifying affected individuals. The PDE inhibitors have revolutionised the management of ED and oral drug therapy is currently first-line therapy for the condition. These agents act by potentiating the action of intracavernosal NO, thereby leading to a more sustained erection. Sildenafil was the first PDE5 inhibitor to undergo evaluation and has been studied extensively. More recently two other agents, vardenafil and tadalafil, have been introduced. All the drugs have been shown to be effective across a wide range of aetiologies of ED, including diabetes. The drugs have been shown to improve EF domain scores, penetration and maintenance of erection, resulting in more successful intercourse. Their effects are greater at higher doses. Sildenafil and vardenafil are shorter-acting agents, while tadalafil has a longer half-life allowing the user more flexibility in sexual activity. Common adverse effects include headache, nasal congestion and dyspepsia, all actions related to inhibition of PDE5. The drugs are generally well tolerated and withdrawal from the clinical studies as a result of drug-related adverse effects were rare. The use of PDE5 inhibitors in the presence of oral nitrates is absolutely contraindicated. The clinical studies to date have not evaluated the use of one drug in the case of treatment failure with another agent. Sublingual apomorphine, which stimulates central neurogenic pathways, is a new agent and may be a suitable alternative in those patients in whom PDE5 inhibitors are ineffective or contraindicated. In clinical trials, all IIEF domains except sexual desire were found to have improved after apomorphine. The median times to erection in these studies were 18.9 and 18.8 minutes for the 2 and 3mg doses, respectively. Intraurethral and intracavernosal alprostadil may be a useful alternative when oral drug therapy is ineffective or contraindicated. The management of ED in the diabetic patient may often involve a multidisciplinary approach where psychosexual counselling and specialist urologist advice is required in addition to the skills and expertise of the diabetologist. Finally, the introduction of the new oral agents have completely revolutionised the management of ED and allowed more individuals to come forward for treatment.
Although medication can help extend the lives of men with chronic heart failure, several factors associated with this disease can interfere with a person's ability to engage in and enjoy sexual activities. Fatigue, depression, medication side effects and the fear of damaging the heart can cause people with chronic heart failure to lose interest in sex or wonder whether this activity is safe for them.

Table 3Metabolic Equivalent (MET) Values for Various Physical Activities56x56Wallis, RM, Corbin, JD, Francis, SH, and Ellis, P. Tissue distribution of phosphodiesterase families and the effects of sildenafil on tissue cyclic nucleotides, platelet function, and the contractile responses of trabeculae carneae and aortic rings in vitro. Am J Cardiol. 1999; 83: 3C–12C

Some blood pressure medicines can also cause erectile dysfunction. Thiazide diuretics and beta-blockers are most likely to cause problems, but this is not a common effect of these medicines and will not happen to everyone. If you are taking either of these medicines and are worried about erectile dysfunction, your GP may be able to change your medicines.

Crossref | PubMed | Scopus (174) | Google ScholarSee all References This study concluded that patients who have stable coronary artery disease who can exercise to 4.5 metabolic equivalents (METs) with a negative or mildly positive stress test and without angina or hypotension can safely take sildenafil. Physicians who prescribe sildenafil should counsel their patients that, if they have chest pain or other cardiac symptoms with sexual intercourse, they should not take nitrates and should immediately call their physician.66x66Jackson, G. Sexual intercourse and stable angina pectoris. Am J Cardiol. 2000; 86: 35F–37F
The prevalence of erectile dysfunction is approximately 2-fold higher in hypertensive patients compared to normotensive individuals. However, erectile dysfunction remains under-reported, under-recognized, and under-treated in hypertensive patients. Hypertension per se and antihypertensive drug therapy may contribute to the development of erectile dysfunction in patients with arterial hypertension. The management of erectile dysfunction in hypertensive patients is tricky and should take into account the different effects of antihypertensive drug categories on erectile function. Lifestyle modification should be the mainstay of treating erectile dysfunction in patients with untreated hypertension. Switching antihypertensive therapy should be considered in treated hypertensive patients, unless administered drugs are absolutely indicated for the individual patient. Otherwise, PDE-5 inhibitors should be used, since they are both effective and safe in hypertensive patients. Finally, erectile dysfunction offers the opportunity to recognize asymptomatic cardiovascular disease and better characterize the relevant risk with obvious benefits for cardiovascular disease prevention.

Figure. Progression of atherosclerosis. Endothelial dysfunction occurs early in atherosclerosis and prevents blood vessels from dilating properly. When the blood vessels that supply the penis are not able to dilate during sexual stimulation because of endothelial dysfunction, the penis cannot fill with blood, and the man develops erectile dysfunction. As atherosclerosis progresses, plaques build up in blood vessels and blood flow is slowed, further worsening erectile function. A heart attack occurs when an atherosclerotic plaque in a coronary artery ruptures, a blood clot forms over the plaque, and blood flow to the heart muscle is completely blocked. Atherosclerotic risk factors (black arrows) worsen cardiovascular health; modification of these risk factors (red arrows) improves cardiovascular health.
But closer questioning often revealed a very different story—men would admit that struggles to achieve an erection usually preceded a heart attack or other cardiac event by one, two, or three years. Back then, the pattern of erectile dysfunction and cardiac disease was so widespread, that most in the medical profession attributed it to simple “aging,” as common as wrinkles and constipation.
The obvious risks are the same that accompany any surgery: infection, pain, bleeding, and scarring. If for some reason the prosthesis or parts become damaged or dislocated, surgical removal may be necessary. With a general success rate of about 90 percent, any of the devices will restore erections, but they will not affect sexual desire, ejaculation, or orgasm.
Abstract | PubMed | Scopus (136) | Google ScholarSee all References In a prospective review of 3250 men aged 26 to 83 years without ED at their first examination, total cholesterol and high-density lipoprotein (HDL) cholesterol levels were found to be strongly predictive of onset of ED after controlling for age, diabetes mellitus, stress level, cardiovascular disease, and prostate disease.25x25Wei, M, Macera, CA, Davis, DR, Hornung, CA, Nankin, HR, and Blair, SN. Total cholesterol and high density lipoprotein cholesterol as important predictors of erectile dysfunction. Am J Epidemiol. 1994; 140: 930–937
Yohimbe. Before Viagra and the other prescription erectile dysfunction drugs became available, doctors sometimes prescribed a derivative of the herb yohimbe (yohimbine hydrochloride) to their patients suffering from ED. But experts say the medication is not particularly effective, and it can cause jitteriness and other problems. "It's not a great drug," says McCullough. "And I suspect the herb is not as potent as the pharmaceutical version." What's more, evidence shows that yohimbe is associated with high blood pressure, anxiety, headache, and other health problems. Experts discourage its use.
Montorsi F,  Briganti A,  Salonia A,  Rigatti P,  Margonato A,  Macchi A,  Galli S,  Ravagnani PM,  Montorsi P. Erectile dysfunction prevalence, time of onset and association with risk factors in 300 consecutive patients with acute chest pain and angiographically documented coronary artery disease, Eur Urol , 2003, vol. 44 (pg. 360-364)https://doi.org/10.1016/S0302-2838(03)00305-1
A number of nonprescription products claim to be herbal forms of Viagra. Some of these products contain unknown amounts of ingredients similar to those in prescription medications, which can cause dangerous side effects. Some actually contain the real drug, which should be given by prescription only. Although the Food and Drug Administration has banned many of these products, some potentially dangerous erectile dysfunction remedies remain on the market.

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Abstract | Full Text | Full Text PDF | PubMed | Scopus (58) | Google ScholarSee all References Avoiding sexual activity between 6 AM and noon may be recommended to higher-risk patients because this is the time of peak incidence of most arrhythmias, myocardial ischemia, sudden cardiac death, and cerebrovascular accidents.1x1Muller, JE. Sexual activity as a trigger for cardiovascular events: what is the risk?. Am J Cardiol. 1999; 84: 2N–5N
Abstract | PubMed | Scopus (136) | Google ScholarSee all References In a prospective review of 3250 men aged 26 to 83 years without ED at their first examination, total cholesterol and high-density lipoprotein (HDL) cholesterol levels were found to be strongly predictive of onset of ED after controlling for age, diabetes mellitus, stress level, cardiovascular disease, and prostate disease.25x25Wei, M, Macera, CA, Davis, DR, Hornung, CA, Nankin, HR, and Blair, SN. Total cholesterol and high density lipoprotein cholesterol as important predictors of erectile dysfunction. Am J Epidemiol. 1994; 140: 930–937

What comes after an ED diagnosis in diabetic patients? Often, Dr. Eid will instantly refer these men to a cardiologist. “If a patient has diabetes and is newly diagnosed, a significant portion of these men are going to develop coronary artery disease in the next 2-3 years,” he said. “One of the things we do is recommend is that they see a cardiologist and perhaps have a stress test or some sort of evaluation.”
Based on this testing, EDDM patients were treated with behavioral therapy, intracavernosal (papaverine, PGE-1, or Trimix) or intraurethral PGE-1, a vacuum constriction device (VCD), or implantation of a penile prosthesis. Novel surgical procedures, ligation of incompetent cavernosal veins or penile revascularization, were seldom efficacious with EDDM and were soon abandoned. Although these nonsurgical therapies were efficacious, they were not widely requested because of their invasive or mechanical nature.
Abstract | Full Text | Full Text PDF | PubMed | Scopus (30) | Google ScholarSee all References Increased cGMP levels cause intracellular calcium levels to decrease, resulting in relaxation of the corporeal smooth muscle, active dilatation of the penile arteries, arterioles, and sinusoids, and finally, increased arterial inflow and passive compression of penile venous outflow.10x10Kloner, RA and Zusman, RM. Cardiovascular effects of sildenafil citrate and recommendations for its use. Am J Cardiol. 1999; 84: 11N–17N
Gazzaruso C,  Solerte SB,  Pujia A,  Coppola A,  Vezzoli M,  Salvucci F,  Valenti C,  Giustina A,  Garzaniti A. Erectile dysfunction as a predictor of cardiovascular events and death in diabetic patients with angiographically proven asymptomatic coronary artery disease: a potential protective role for statins and 5-phosphodiesterase inhibitors, J Am Coll Cardiol , 2008, vol. 51 (pg. 2040-2044)https://doi.org/10.1016/j.jacc.2007.10.069
The cardiovascular adverse effects of sildenafil use have been studied extensively. Phosphodiesterase type 5, although located primarily in the genitalia, also can be found throughout the systemic vasculature, although other PDEs predominate there10x10Kloner, RA and Zusman, RM. Cardiovascular effects of sildenafil citrate and recommendations for its use. Am J Cardiol. 1999; 84: 11N–17N

For patients who failed oral medical therapy or unable to tolerate the side effects, intracavernosal injection of vasoactive agents can often provide effective alternative. Various vasoactive agents such as alprostadil, papaverine or phentolamine have been used either as single agent or combination agents to potentiate the NO release and cavernosal smooth muscle vasodilation. However, intracavernosal injection therapy has high attrition rate and can be associated pain especially with alprostadil injection (2). The practice of isolating compounds and understanding its pharmacological attributes before using it as a drug therapy has been a strength of Western medicine.
The natural history of ED in people with diabetes is normally gradual and does not occur overnight. Both vascular and neurological mechanisms are most commonly involved in people with diabetes. Atherosclerosis in the penile and pudendal arteries limits the blood flow into the corpus cavernosum. Because of the loss of compliance in the cavernous trabeculae, the venous flow is also lost. This loss of flow results in the inability of the corpora cavernosae to expand and compress the outflow vessels.
Crossref | Google ScholarSee all References Other investigators have suggested these medications may exert a hormonal effect. β-Blockers have been associated with decreased free and total testosterone levels in placebo-controlled trials.39x39Rosen, RC and Weiner, DN. Cardiovascular disease and sleep-related erections. J Psychosom Res. 1997; 42: 517–530
Erectile dysfunction (ED) is a common disorder that affects the quality of life of many patients. It is prevalent in more than half of males aged over 60 years. Increasing evidence suggests that ED is predominantly a vascular disorder. Endothelial dysfunction seems to be the common pathological process causing ED. Many common risk factors for atherosclerosis such as diabetes, hypertension, smoking, obesity and hyperlipidaemia are prevalent in patients with ED and so management of these common cardiovascular risk factors can potentially prevent ED. Phosphodiesterase type 5 inhibitors provide short-term change of haemodynamic factors to help initiate and maintain penile erection. They have been shown to be an effective and safe treatment strategy for ED in patients with heart disease, including those with ischaemic heart disease and hypertension.
Preclinical and clinical trials of these oral agents have clearly demonstrated that they are well tolerated by most DM patients and have an efficacy rate superior to other oral agents. The ultimate result is an improved quality of life (QOL) in EDDM patients. With a greater willingness of DM patients to discuss and seek treatment for ED, it is highly probable that the use of these oral agents will continue to increase. The goal of this article is to provide the physician and pharmacist with a background and working knowledge of these oral agents and their present-day alternatives.
In many of these cases, a discussion between the physician, the man with erectile dysfunction, and possibly his partner can help to resolve the issues leading to treatment failure. For men who experience severe side effects, can’t take the drugs for other reasons (such as taking medicines such as nitroglycerin), or don’t respond in spite of further education on the correct use of the drugs, there are other treatment options that can help most men remain sexually active.
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