Penile arterial supply (top) and venous drainage (middle), longitudinal views. Bottom, Transverse and longitudinal views of venous return. From Lue TF. Physiology of penile erection and pathophysiology of erectile dysfunction and priapism. In: Walsh PC, Retik AB, Vaughan ED Jr, Wein AJ, eds. Campbell's Urology. Vol 2. 7th ed. Philadelphia, Pa: WB Saunders Co; 1998:1157-1179. With permission from Elsevier.
If you can't take one of these oral medications, your physician may have you try Caverject (alprostadil for injection), a hormone that you inject into your penis using a fine needle, or Muse (alprostadil urogenital), a tiny suppository that you insert into the tip of the penis. Both of these will bring on an erection within five to 15 minutes without sexual stimulation.

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
People sometimes refer to ED as "impotence," although the two aren't really the same condition. ED is the physical inability to develop or maintain an erection that is rigid enough for sex. Impotence is a broader term. While one cause of it is ED, impotence may also involve a lack of sexual desire, an inability to ejaculate, or problems with orgasm.
In some cases, however, these drugs may be unsuitable for patients with heart disease. If you are considering one of these drugs and you have heart disease, as many diabetics do, be sure to tell your doctor. In rare cases, the pills may create “priapism,” a prolonged and painful erection lasting six hours or more (although reversible with prompt medical attention).
Abstract | Full Text | Full Text PDF | PubMed | Scopus (58) | Google ScholarSee all References Theoretically, the risk of a cardiac event during sexual activity should be increased. Sexual activity is associated with an elevated heart rate, blood pressure level, and myocardial oxygen demand, and this increase in hemodynamic stress may result in myocardial ischemia.79x79Kimmel, SE. Sex and myocardial infarction: an epidemiologic perspective. Am J Cardiol. 2000; 86: 10F–13F
Abstract | PubMed | Scopus (136) | Google ScholarSee all References Another study evaluated 32 hypertensive men with ED and 78 normotensive men with ED with regard to age, body mass index, hormonal profile, penile arterial flow, risk factors for arterial disease, psychiatric disease, and neurologic disease measured by pudendal nerve conduction studies.30x30Jaffe, A, Chen, Y, Kisch, ES, Fischel, B, Alon, M, and Stern, N. Erectile dysfunction in hypertensive subjects: assessment of potential determinants. Hypertension. 1996; 28: 859–862
There are other treatment options for erectile dysfunction (ED). Alprostadil is a medication that improves blood flow to the penis and improves erections. It can be given either by injection (Caverject and other brands) at the base of the penis or by putting an alprostadil gel (brand name MUSE) directly into the urethra, using a thin tube and a little lubricant so it slides in easily. The medicine is absorbed from the lining of the urethra into the surrounding tissues. The shot is less appealing to most people, of course, but more effective.

Crossref | PubMed | Scopus (23) | Google ScholarSee all References, 73x73Rajagopalan, P, Mazzu, A, Xia, C, Dawkins, R, and Sundaresan, P. Effect of high-fat breakfast and moderate-fat evening meal on the pharmacokinetics of vardenafil, an oral phosphodiesterase-5 inhibitor for the treatment of erectile dysfunction. J Clin Pharmacol. 2003; 43: 260–267


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Crossref | Google ScholarSee all References Different classes of β-blockers have been postulated to have differential effects on erectile function, with the nonselective β-blockers (eg, propranolol) having more deleterious effects than the more cardioselective medications (eg, atenolol, metoprolol).42x42Weiss, RJ. Effects of antihypertensive agents on sexual function. Am Fam Physician. 1991; 44: 2075–2082
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.
The impact of third-generation cardioselective beta-blockers such as carvedilol and nebivolol has also been investigated. Fogari et al. investigated the effect of carvedilol on erectile function in a double-blind crossover study involving 160 men newly diagnosed with hypertension and found chronic worsening of sexual function in those treated with carvedilol compared with valsartan and placebo.24
Sexual intercourse is an infrequent cause of myocardial infarction. In a study of 1774 patients after myocardial infarction, only 1.5% of these events occurred within 2 hours of sexual intercourse, and sexual activity was considered a direct contributing factor in 0.9%.8x8Muller, JE, Mittleman, A, Maclure, M, Sherwood, JB, Tofler, GH, and Determinants of Myocardial Infarction Onset Study Investigators. Triggering myocardial infarction by sexual activity: low absolute risk and prevention by regular physical exertion. JAMA. 1996; 275: 1405–1409
PubMed | Google ScholarSee all References The risk of ED was 1.83 times higher in men with a total cholesterol level greater than 240 mg/dL as opposed to less than 180 mg/dL. Also, an HDL cholesterol level greater than 60 mg/dL was found to be protective against the development of ED. In the MMAS, HDL cholesterol levels were noted to have an inverse relationship with the presence of ED.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
For oral erectile dysfunction medicines to work as desired, they must be used properly in the first place. This means taking the medicine 30–45 minutes before engaging in sexual intimacy; taking the drug on an empty stomach or at least avoiding a heavy or high-fat meal before taking the drug (this is especially important when using sildenafil); and engaging in adequate genital stimulation before attempting intercourse. Drinking small amounts of alcohol (one to two drinks) should not compromise the effectiveness of erectile dysfunction medicines, but larger amounts of alcohol can diminish a man’s ability to have an erection.
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