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.
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.
Levine GN,  Steinke EE,  Bakaeen FG,  Bozkurt B,  Cheitlin MD,  Conti JB,  Foster E,  Jaarsma T,  Kloner RA,  Lange RA,  Lindau ST,  Maron BJ,  Moser DK,  Ohman EM,  Seftel AD,  Stewart WJ. Sexual activity and cardiovascular disease: a scientific statement from the American Heart Association, Circulation , 2012, vol. 125 (pg. 1058-1072)https://doi.org/10.1161/CIR.0b013e3182447787
Abstract | Full Text | Full Text PDF | PubMed | Scopus (53) | Google ScholarSee all References Coital position has not been shown to play a role in increased cardiovascular risk; similar peak heart rates and blood pressure levels are evident with either the man or the woman in the superior position during intercourse.90x90Nemec, ED, Mansfield, L, and Kennedy, JW. Heart rate and blood pressure responses during sexual activity in normal males. Am Heart J. 1976; 92: 274–277
Abstract | Full Text | Full Text PDF | PubMed | Scopus (66) | Google ScholarSee all References Although some case studies have reported a relationship between calcium channel blockers and ED, most studies suggest that this effect is minimal and that any relationship is likely secondary to a decrease in blood pressure with consequent reflex sympathetic activation.42x42Weiss, RJ. Effects of antihypertensive agents on sexual function. Am Fam Physician. 1991; 44: 2075–2082
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.
Abstract | Full Text | Full Text PDF | PubMed | Scopus (259) | Google ScholarSee all References Sildenafil should be used with caution in patients with liver dysfunction or renal impairment, as well as in patients taking any medications that inhibit the P-450 pathway such as cimetidine or erythromycin.3x3Zusman, RM, Morales, A, Glasser, DB, and Osterloh, IH. Overall cardiovascular profile of sildenafil citrate. Am J Cardiol. 1999; 83: 35C–44C
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).
Normal penile erection is controlled by two mechanisms: reflex erection and psychogenic erection. Reflex erection occurs by directly touching the shaft of the penis, while psychogenic erection occurs by erotic or emotional stimuli. ED is a condition where erection does not take place by either mechanism. ED can occur because of hormonal imbalance, neural disorders or lack of adequate blood supply to the penis.54 Lack of blood supply can be a result of impaired endothelial function associated with CAD.54

Crossref | PubMed | Scopus (528) | Google ScholarSee all References Sildenafil also has good efficacy in patients with ischemic heart disease, as shown by a retrospective subanalysis of data from 11 double-blind, placebo-controlled studies involving 3672 patients with ED and ischemic heart disease who were not taking nitrates.59x59Kloner, RA. Cardiovascular risk and sildenafil. Am J Cardiol. 2000; 86: 57F–61F
The medications used to treat high blood pressure do not take into account the symptoms of erectile dysfunction, as their intention is to lower the blood pressure to a more manageable state, reducing the stress put on blood vessels. High blood pressure and ED are seen as separate entities, with the former taking priority for pharmaceutical treatment. This means that the medications used might do nothing to cure erectile dysfunction and may, in fact, prolong it. Medications that lower blood pressure might actually cause a low blood pressure state in the groin area and the arteries supplying the penis, making it near impossible to achieve an erection. The following are examples of such medications:

Now that we better appreciate the complex sequence of events necessary for erections to occur, it’s no surprise that testosterone alone yields less than perfect results. Erectile dysfunction represents more than just low testosterone, which is just one facet of the spectrum of dysfunctional phenomena that cause sexual dysfunction. Nonetheless, when testosterone is combined with popular drugs like Viagra®, success is enhanced to an even greater degree—orgasmic function improves, along with erectile capacity and libido.20 Testosterone also activates penile nitric oxide; ultrasound studies have demonstrated a 27% increase in arterial blood flow into the penis with testosterone supplementation.23
Sexual dysfunction refers to a problem during any phase of the sexual response cycle that prevents the individual or couple from experiencing satisfaction from the sexual activity. The sexual response cycle has four phases: excitement, plateau, orgasm, and resolution. Sexual dysfunction can be caused by physical and emotional factors, or a combination of both. The side effects of some medications also can lead to sexual dysfunction.
Abstract | Full Text | Full Text PDF | PubMed | Scopus (95) | Google ScholarSee all References Vision changes are described most frequently as an increased perception of bright lights, a blue-green tinge to observed colors, or blurred vision. Sildenafil has no direct effect on platelet function but potentiates the inhibitory effect of sodium nitroprusside on adenosine diphosphate–induced platelet aggregation ex vivo.56x56Wallis, 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
Sildenafil should be taken 1–2 h before intercourse. It is important to tell patients that the drug’s effectiveness requires sexual stimulation. One patient in our clinic recently complained that he had no effect from taking sildenafil. It was later discovered that he took the pill and then sat on his couch and read a book about how to grow tomatoes!
Experimental in vivo studies have implicated central and peripheral neuropathy, impaired neurotransmission, and endothelial dysfunction in the pathogenesis of diabetic ED.26,27 Copulatory behavior and penile reflexes are uniformly impaired 4–12 months after the onset of diabetes in the BB rat.26,27 McVary et al.26 found that peripheral neuropathy accounts for only part of the dysfunctional findings, and that spinal sexual reflexes were also severely impaired.
Men with diabetes tend to develop erectile dysfunction 10 to 15 years earlier than men without diabetes. As men with diabetes age, erectile dysfunction becomes even more common. Above the age of 50, the likelihood of having difficulty with an erection occurs in approximately 50% to 60% of men with diabetes. Above age 70, there is about a 95% likelihood of having some difficulty with erectile dysfunction.
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