Before a man concludes that oral drugs don’t work for him, he should have his testosterone levels checked to rule out hormone deficiency as the cause of (or as a contributor to) his sexual dysfunction. Other symptoms of low testosterone include a low sex drive and infertility. Checking testosterone levels requires a blood test. If a man’s levels of testosterone are decreased or at the lower end of normal, his doctor may prescribe supplemental testosterone therapy, either as testosterone injections or testosterone gel, which is applied daily to the skin. In some cases, testosterone therapy alone can resolve sexual dysfunction, or it can be combined with the use of oral erectile dysfunction drugs.

Neurological (nerve and brain) diseases: The nervous system plays a vital part in achieving and maintaining an erection. It is common for men with conditions such as stroke, multiple sclerosis (MS), Alzheimer’s disease, Parkinson’s disease, and spinal cord injuries to experience ED. This is due to an interruption in the transmission of nerve impulses between the brain and the penis.
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Penile Injection Medication: This is just what it sounds like. Injected at home directly into the penis, the medication alprostadil produces erection by relaxing certain muscles, increasing blood flow into the penis and restricting outflow. Although some sources report an 80 percent success rate, the therapy has disadvantages, such as risks of infection, pain, and scarring—fibrosis—in the penis, and it may also cause priapism. A popular version of this medication is Upjohn Corporation’s Caverject. The MUSE System, by VIVUS, involves the same medicine (a pellet of alprostadil) applied with an eye-dropper-like applicator, directly into the urethra.
Basaria S,  Coviello AD,  Travison TG,  Storer TW,  Farwell WR,  Jette AM,  Eder R,  Tennstedt S,  Ulloor J,  Zhang A,  Choong K,  Lakshman KM,  Mazer NA,  Miciek R,  Krasnoff J,  Elmi A,  Knapp PE,  Brooks B,  Appleman E,  Aggarwal S,  Bhasin G,  Hede-Brierley L,  Bhatia A,  Collins L,  LeBrasseur N,  Fiore LD,  Bhasin S. Adverse events associated with testosterone administration, N Engl J Med , 2010, vol. 36 (pg. 109-122)https://doi.org/10.1056/NEJMoa1000485
Abstract | Full Text PDF | PubMed | Scopus (16) | Google ScholarSee all References These medications cause intracavernosal pressure changes in animal models, and human studies have noted deleterious effects on erectile function, decreased libido, and ejaculatory problems.42x42Weiss, RJ. Effects of antihypertensive agents on sexual function. Am Fam Physician. 1991; 44: 2075–2082

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

Intracavernosal and intraurethral injections are second-line therapy for patients with ED. Alprostadil is the agent most commonly used for intracavernosal injections. The main adverse effects of intracavernosal injections are painful erection, priapism and development of scarring at the injection site.73 Alprostadil is also available as a topical cream in patients who cannot tolerate injections.75
Crossref | PubMed | Scopus (539) | Google ScholarSee all References Sleep studies in 175 patients with hypertension and erectile problems showed significantly lower penile rigidity measured by strain gauge plethysmography compared with 110 normotensive male controls with similar subjective erectile problems.33x33Hirshkowitz, M, Karacan, I, Gurakar, A, and Williams, RL. Hypertension, erectile dysfunction, and occult sleep apnea. Sleep. 1989; 12: 223–232
Crossref | PubMed | Scopus (539) | Google ScholarSee all References After adjusting for age, vascular disease, psychiatric disease, hormonal factors, and marital status, a study of 4462 US Army veterans aged 31 to 49 years found an odds ratio of 1.8 for the risk of developing ED in men who smoked.26x26Mannino, DM, Klevens, RM, and Flanders, WD. Cigarette smoking: an independent risk factor for impotence?. Am J Epidemiol. 1994; 140: 1003–1008
Relaxation of erectile tissue requires nitric oxide from nonadrenergic-noncholinergic neurons and the endothelium.21 Penile tissue from diabetic men with ED demonstrates impaired neurogenic and endothelium-mediated relaxation of smooth muscle,22 increased accumulation of advanced glycation end products (AGEs),23 and upregulation arginase, a competitor with nitric oxide synthase for its substrate L-arginine.24 Normal responses to direct smooth muscle relaxants in most of these studies implies that the impairments are due to decreased synthesis, release, or activity of nitric oxide. The fundamental mechanisms mediating these changes are thought to be the same as for other diabetic complications: increased polyol pathway flux, intracellular accumulation of AGEs, activation of protein kinase C, and increased flux through the hexosamine pathway.25
4. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Erectile dysfunction (updated Nov 2015). https://www.niddk.nih.gov/health-information/health-topics/urologic-disease/erectile-dysfunction/Pages/facts.aspx (accessed Nov 2016). myDr myDr provides comprehensive Australian health and medical information, images and tools covering symptoms, diseases, tests, medicines and treatments, and nutrition and fitness.Related ArticlesImpotence causesFind out the physical and psychological causes of impotence, also called erectile dysfunction or ED.Erectile dysfunction: visiting your doctorFind out what questions a doctor may ask when discussing erectile dysfunction (ED, or impotence8 Surprising causes of erectile dysfunctionOccasional erectile dysfunction is not uncommon, but if it's persistent, erectile dysfunction caAdvertisement
Erectile dysfunction is frequent in patients with established CAD with prevalence rates ranging between 47 and 75% in studies.2,4,14 The AssoCiatiOn Between eRectile dysfunction and coronary Artery disease (COBRA) trial tested the hypothesis that the ED rate differs in CAD patients according to the clinical presentation (acute vs. chronic coronary syndromes) and the extent of vessel involvement (one vs. two to three vessel disease)15 (Figure 3). The overall ED prevalence in CAD patients was 47%, whereas in the normal coronary angiography group the ED rate was 24%. When separately considered, the ED rate was 22% in patients with acute coronary syndromes (ACS) and one-vessel disease and 55 and 65% in patients with ACS and multi-vessel disease and with chronic coronary syndrome, respectively. The study also showed that both severity (IIEF <10) and duration (>24 months) of ED were predictive of severe coronary involvement at angiography. This study offers pathophysiological and mechanistic explanations related to the clinical setting. In patients with multi-vessel disease, regardless of the clinical presentation, the advanced coronary and systemic atherosclerosis is the reason for the high rate of ED. However, in the setting of acute myocardial infarction with one-vessel disease, ED is far less frequent because the atherosclerotic burden is modest (i.e. abrupt occlusion of a single non-obstructing plaque in the absence of extensive atherosclerosis) in both the coronary and penile circulations.15,16
Crossref | PubMed | Scopus (23) | Google ScholarSee all References In some elderly men, tadalafil could be detected in the bloodstream 6 days after oral ingestion.74x74Gresser, U and Gleiter, CH. Erectile dysfunction: comparison of efficacy and side effects of the PDE-5 inhibitors sildenafil, vardenafil and tadalafil—review of the literature. Eur J Med Res. 2002; 7: 435–446
Crossref | PubMed | Scopus (42) | Google ScholarSee all References Apomorphine does not appear to have any notable cardiovascular adverse effects and has been used successfully in Europe. However, apomorphine use has been associated with other unpleasant adverse effects such as nausea and emesis, and the drug has not been approved by the US Food and Drug Administration (FDA) for use in the United States.
Combination therapy has proven effective for some men who don’t respond adequately to oral medicines. The idea is to use two drugs with different mechanisms of action for better results. Commonly, sildenafil is used in combination with pellets of alprostadil (synthetic prostaglandin E1) that are inserted into the urethra (the tube in the penis that carries urine from the bladder to the outside of the body). Alprostadil also increases the blood supply to the penis, but by different means.
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