In subsequent clinical studies, a surprisingly high percentage of EDDM patients–10% to 20%–claimed that the placebo "improved my erections," thus indicating a psychological basis for their ED. In the latter half of the 1980s, objective means were developed that could help determine if a EDDM patient had organic or psychogenic ED. The absence of rigid sleep erections confirmed by penile monitors was one criterion for organic ED. The failure of vasoactive agents (papaverine, Trimix, or prostaglandin E-1 [PGE-1]) injected into the corpora cavernosa to induce penile rigidity was another criterion for organic disease. Intracavernosal maintenance flow rates during pharmacocavernosometry and maximum cavernosal arterial flow during penile Doppler ultrasonography were additional determinants.
Organic nitrates are drugs that widen arteries by increasing their supply of nitric oxide; that's how they open the partially blocked coronary arteries in patients with angina. But because nitrates and ED pills both act on nitric oxide, the drugs don't mix; healthy volunteers given Viagra followed an hour later by nitroglycerin see their blood pressures drop by 25–51 mm Hg, a potentially dangerous amount. All experts agree that men who are taking nitrates cannot use ED pills; this includes all preparations of nitroglycerin (short-acting, under-the-tongue tablets or sprays), long-acting nitrates (isosorbide dinitrate or Isordil, Sorbitrate, and others, and isosorbide mononitrate, Imdur, ISMO, and others), nitroglycerin patches and pastes, and amyl nitrite or amyl nitrate (so-called poppers, which some men use for sexual stimulation).
Abstract | Full Text | Full Text PDF | PubMed | Scopus (272) | Google ScholarSee all References Between 1987 and 1989, the Massachusetts Male Aging Study (MMAS), a community-based random sample observational study of 1709 men, used self-administered sexual activity questionnaires to gather information about noninstitutionalized men aged 40 to 70 years in cities near Boston.4x4Feldman, HA, Goldstein, I, Hatzichristou, DG, Krane, RJ, and McKinlay, JB. Impotence and its medical and psychosocial correlates: results of the Massachusetts Male Aging Study. J Urol. 1994; 151: 54–61
Abstract | Full Text | Full Text PDF | PubMed | Scopus (24) | Google ScholarSee all References Withdrawal of sexual stimulation causes a return of sympathetic tone and degradation of cGMP, predominantly by phosphodiesterase type 5 (PDE-5) within the trabecular smooth muscle.11x11Nehra, A. Intracavernosal therapy: when oral agents fail. Curr Urol Rep. 2001; 2: 468–472
The mechanisms of action by which antihypertensive medications cause ED are currently unknown. Some investigators have theorized that antihypertensive medications affect erectile function by decreasing blood pressure, which reduces the perfusion pressure needed to maintain sufficient blood flow for erections through atherosclerotic penile arteries.37x37Benet, AE and Melman, A. The epidemiology of erectile dysfunction. Urol Clin North Am. 1995; 22: 699–709
Most studies into the effect of beta-blockers on ED point to negative effects of first- and second-generation beta-blockers, while beta-blockers with vasodilating effects can improve erectile function. Alpha-blockers, calcium channel blockers, and angiotensin-converting enzyme inhibitors seem to have a neutral effect on erectile function. Multiple previous studies have demonstrated a beneficial effect of angiotensin receptor blockers on erectile function and they should probably be the favoured antihypertensive agents in patients with ED.29
Inflatable prostheses are complex mechanical devices that imitate the natural process of erection. Parts are inserted surgically into the penis and scrotum, and activated by squeezing. When erection is no longer desired, a valve on the pump is pressed, and the penis becomes flaccid. Self-contained single-unit prostheses are similar to the inflatable types, but more compact. The entire device is implanted into the penis. When erection is desired, the unit is activated by either squeezing or bending, depending on which of the two types of self-contained prostheses is used.
Counselling or sex therapy (58% of people find this works for them) –mind-related causes of erectile dysfunction can affect anyone. They are more likely if you experience erectile dysfunction at a younger age. Talking to a counsellor or therapist can help some people overcome erectile dysfunction related to these problems, possibly for good. They can also help you if your erectile dysfunction is causing you stress, as this can make matters worse.
Crossref | PubMed | Google ScholarSee all References Risk factors for cardiovascular disease include diabetes mellitus, obesity, physical inactivity, hyperlipidemia, tobacco use, and hypertension. Often, the relative risk of each of these factors in the development of ED is difficult to assess because many patients with ED and cardiovascular disease have more than 1 risk factor. Another important consideration is the effect of cardiac disease itself on erectile function. A history of a prior myocardial infarction was not found to be a significant independent risk factor for ED in a study comparing sexual function in 50 patients who had a prior myocardial infarction with a control group of 50 patients.14x14Dhabuwala, CB, Kumar, A, and Pierce, JM. Myocardial infarction and its influence on male sexual function. Arch Sex Behav. 1986; 15: 499–504
Olsson et al. conducted a randomised, double-blind, placebo-controlled, parallel group, and flexible dose study in 224 men with ED and one CVD, including IHD (20 %) and hypertension (80 %). This study reported that the sildenafil-treated group showed 71 % improvement in ED compared with the placebo-controlled group (24 %).64 Furthermore, no treatment-related cardiovascular adverse events were reported.65 Conti et al. showed in an early study that sildenafil is an effective treatment for ED in patients with IHD; the majority of patients reported improvement in penile erection with it.66 Another double-blind, placebo-controlled study of patients with ED and stable CAD showed statistically significant improvement with sildenafil versus placebo in both the frequency of penetration and frequency of maintained erections after penetration.67
Crossref | PubMed | Scopus (47) | Google ScholarSee all References Because of this perceived increase in risk, many couples are concerned about resuming sexual activity in the setting of cardiac disease. A study that monitored male patients after coronary artery bypass grafting found that 17% of patients and 35% of their partners were afraid of resuming sexual activity.1x1Muller, JE. Sexual activity as a trigger for cardiovascular events: what is the risk?. Am J Cardiol. 1999; 84: 2N–5N
Second-generation cardioselective beta-blockers (atenolol, metoprolol, bisoprolol, etc.) can also lead to ED. Atenolol was shown to cause significant reduction of sexual activity compared with placebo in a double-blind, parallel-arm study.22 The same study also showed a significant reduction in testosterone levels with atenolol versus valsartan. An open, prospective study of hypertensive men treated with atenolol, metoprolol and bisoprolol for at least 6 months showed high prevalence of ED – approaching 66 % – in these patients.23
medicines called alpha-blockers such as Hytrin (terazosin
HCl), Flomax (tamsulosin HCl), Cardura (doxazosin
mesylate), Minipress (prazosin HCl), Uroxatral (alfuzosin HCl),
 Jalyn (dutasteride and tamsulosin HCl), or Rapaflo (silodosin).
Alpha-blockers are sometimes prescribed for prostate
problems or high blood pressure. In some patients, the use
of Sildenafil with alpha-blockers can lead to a drop in blood pressure or to fainting

This form of therapy has a response rate of well over 70%. The sympathetic nervous system normally maintains the penis in a flaccid or non-erect state. All of the vasoactive drugs, when injected into the corpora cavernosae, inhibit or override sympathetic inhibition to encourage relaxation of the smooth muscle trabeculae. The rush of blood engorges the penile corpora cavernosae sinusoidal spaces and creates an erection.
A sexually competent male must have a series of events occur and multiple mechanisms intact for normal erectile function. He must 1) have desire for his sexual partner (libido), 2) be able to divert blood from the iliac artery into the corpora cavernosae to achieve penile tumescence and rigidity (erection) adequate for penetration, 3) discharge sperm and prostatic/seminal fluid through his urethra (ejaculation), and 4) experience a sense of pleasure (orgasm). A man is considered to have ED if he cannot achieve or sustain an erection of sufficient rigidity for sexual intercourse. Most men, at one time or another during their life, experience periodic or isolated sexual failures. However, the term “impotent” is reserved for those men who experience erectile failure during attempted intercourse more than 75% of the time.

Erectile dysfunction is an accurate predictor of heart attacks and strokes in the future. Psychogenic components play a role in erectile dysfunction, but the most common and primary cause in most men is organic vascular insufficiency, meaning not enough blood gets to the penis. Erectile dysfunction usually occurs one to five years before a male manifests overt signs of cardiovascular disease. The first sign may be death.

Abstract | Full Text | Full Text PDF | PubMed | Scopus (30) | Google ScholarSee all References Penile sympathetic stimulation flows through several pathways, including the sympathetic chain ganglia, which also supply such structures as the heart and vascular system. Sympathetic tone precipitates release of norepinephrine from penile adrenergic nerves, resulting in tonic contraction of cavernosal smooth muscle and its vasculature, thereby keeping the penis flaccid.9x9Andersson, K and Stief, C. Penile erection and cardiac risk: pathophysiologic and pharmacologic mechanisms. Am J Cardiol. 2000; 86: 23F–26F
Abstract | Full Text | Full Text PDF | PubMed | Scopus (66) | Google ScholarSee all References Overall, sexual intercourse does not lead to an extremely exaggerated heart rate or blood pressure level when performed in a familiar setting with one's usual partner.82x82Hellerstein, HK and Friedman, EH. Sexual activity and the postcoronary patient. Arch Intern Med. 1970; 125: 987–999
Penile prosthesis implant remains the most effective and permanent treatment for ED. Penile prosthesis implants can be broadly divided into malleable and inflatable prostheses (20). Malleable penile prosthesis, also known as semi-rigid prosthesis, does not allow for (physiological) flaccid state of the penis. The patient can bend the prosthesis upwards for sexual intercourse and downwards for concealment. Although the angle of prosthesis concealment has improved with recent devices, however due to the constant rigid state of the penis, they are still less comfortable compared to their inflatable counterparts, are more likely to cause social embarrassment and associated with higher risk of implant erosions (21). However, malleable prosthesis still has its place for the treatment of ED as these implants are easier to handle, easier to place and would benefit patients with impaired manual dexterity.

Some doctors prefer to start a man on the lowest dose of an oral medicine and increase the dose until an effective one is found. Others prefer to start with the highest dose and go to a lower dose only if a man complains of side effects. In either case, it’s important for a man to communicate with his doctor to let him know how the dose he’s using is working.
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