Erectile dysfunction

Erectile dysfunction (ED) is the failure to achieve a penile erection suitable for sexual intercourse. Patients often refer to it as impotence. 

ED can result from an abnormality in one of the four systems necessary for a normal penile erection or from a combination of abnormalities. Vascular, nervous, or hormonal etiologies of ED are referred to as organic ED. Abnormality of the fourth system (i.e., patient s psychological receptivity to sexual stimuli) is referred to as psychogenic ED. 

The penis has two corpora cavernosa, which have many interconnected sinuses that fiU with blood to produce an erection. The penis also has one corpus spongiosum, which surrounds the urethra and forms the glans penis. Acetylcholine works with other neurotransmitters (i.e., cyclic guanylate monophosphate, cyclic adenosine monophosphate, vasoactive intestinal polypeptide) to produce penile arterial vasodilation and ultimately an erection. Causes of organic ED include diseases that compromise vascular flow to the corpora cavernosum (e.g., peripheral vascular disease, arteriosclerosis, essential hypertension), impair nerve conduction to the brain (e.g., spinal cord injury, stroke), and are associated with hypogonadism (e.g., prostate or testicular cancer, hypothalamic or pituitary disorders). 

Causes of psychogenic ED include malaise, reactive depression or performance anxiety, sedation, Alzheimer s disease, hypothyroidism, and mental disorders. Patients with psychogenic ED generally have a higher response rate to interventions than patients with organic ED. 

Social habits (e.g., cigarette smoking, excessive ethanol intake) and medications (Table 83-1) can also cause ED. 

UROLOGICAL DRUGS ERECTILE DYSFUNCTION Phosphodiesterase type 5 inhibitors 

Primary drug Secondary drug ERECTILE DYSFUNCTION Effect Mechanism Precautions 

ALPROSTADIL - Drugs Used in Obstetrics and Gynaecology, Prostaglandins  

PHOSPHODIESTERASE TYPE S INHIBITORS MACROLIDES t phosphodiesterase type 5 inhibitor levels with erythromycin, and possibly clarithromycin and telithromycin Inhibition of metabolism. 1 dose of these phosphodiesterase type 5 inhibitors (e.g. start vardenafil at 5 mg) 

TADALAFIL RIFAMPICIN L tadalafil levels Probable induction of metabolism Watch for poor response 

The approved drugs for erectile dysfunction (ED) all share the same mode of action, which is inhibition of phosphodiesterase type 5 (PDE5). PDE5 hydrolyzes the phosphodi-ester of cyclic GMP (cGMP). Elevated levels of cGMP relax the muscle tissue that lines the blood vessels of the corpus cavernosum in the penis. Blood freely enters the tissue, 

Although ED does not pose the same level of health risk as bacterial infections and diabetes, ED drugs have been hugely profitable for their manufacturers. The drugs have been widely advertised and even promoted by Bob Dole, a former U.S. senator and candidate for U.S. president. The drugs have also drawn criticism due to abuse by recreational users. 

Impotence—A variety of endocrine, vascular, neurological, and psychiatric diseases disrupt normal sexual and 

Cerebrovascular accidents Cervical spondylosis Multiple sclerosis Parkinson s disease Pelvic trauma 

Abdominoperineal resection Aortoiliac surgery Bilateral orchiectomy Cystectomy Genital trauma Inguinoscrotal surgery Internal urethrotomy  

Primary autonomic insufficiency Primary and metastatic tumors Spinal arachnoiditis Spinal cord trauma Syphilis 

Prostatectomy radical or simple Renal transplantation Retroperitoneal lymphadenectomy Spinal cord injury Sympathectomy 

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Therapeutic opportunities for NO synthons include angina, for which nitroglycerin is effectively used, as well as penile erectile dysfunction. NOS inhibitors have demonstrated some protection in cerebral ischemia models and may be potentially beneficial in alleviating cell death associated with cerebral ischemia. l-NMA is under clinical study for treatment of sepsis. 

Nitric oxide (NO) is a minor but villainous component of the atmosphere. It is involved in the formation of both smog (Chapter 11) and acid rain (Chapter 14). You may be surprised to learn that small amounts of NO are also produced in the human body, where it has a generally beneficial effect. In particular, it has the ability to dilate blood vessels, lowering blood pressure and reducing the likelihood of strokes or heart attacks. Beyond that, NO is effective in treating what television commercials refer to as erectile dysfunction it increases blood flow to the penis. 

Erectile dysfunction is treated by local or systemic application of vasodilator drugs. The most effective is sildenafil, a phosphodiesterase-type 5 inhibitor. 

ErbB Receptor Family Erectile Dysfunction ERGIC... 

Recent use (within 24 h of sildenafil or vardenafil or within 48 h of tadalafil) of a phosphodiesterase-5 inhibitor for erectile dysfunction (or pulmonary hypertension)... 

Phosphodiesterase type 5 inhibitors are commonly prescribed for erectile dysfunction and include sildenafil, vardenafil,... 

Phosphodiesterase 5 inhibitors such as sildenafil are effective for MS-induced erectile dysfunction.14 In women, vaginal dryness or dyspareunia may respond to lubricating jellies. 

Decreased libido, decreased energy, erectile dysfunction, impotence, decreased sperm production, infertility, gynecomastia, and rarely, galactorrhea. 

Differentiate between organic and psychogenic erectile dysfunction (ED) and describe the etiology and pathophysiology of each. 

Identify the drug classes most likely to contribute to erectile dysfunction. 

Erectile dysfunction (ED) is defined as the inability to achieve or maintain an erection sufficient for sexual intercourse. The definition is very subjective due to differences in desired or needed rigidity in patients of different ages and in different types of relationships. Patients may refer to their dysfunction as impotence, but the National Institutes of Health Consensus Development Conference recommends that the term erectile dysfunction replace the term impotence due to confusion with other forms of sexual dysfunction and the negative connotation associated with the term impotence.1 Patients may also develop libido or ejaculatory disorders, but these are not considered erectile dysfunction. 

The International Index of Erectile Dysfunction (IIED) is the most widely used questionnaire to assess the severity of ED.10 It consists of 15 questions with 5 domains erectile function, libido, orgasmic function, sexual satisfaction, and overall satisfaction. The erectile function domain has a maximum score of 30 with a score of less than 26 indicating some degree of ED. 

TABLE 48-1. Factors Associated with Erectile Dysfunction... 

FIGURE 48-2. Available devices and prostheses used to treat erectile dysfunction. (From Wagner G, Saenz de Tejada I. Update on male erectile dysfunction. BMJ 1998 316 681, with permission.)... 

From Lee M. Erectile dysfunction. In DiPiro JT, Talbert RL, Yee GC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 1524, with permission. 

American Urological Association. The management of erectile dysfunction an update, 2005 (www.auanet.org/guidelines /edmgmt.cfm). 

Gresser U, 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. 

Ralph D, McNicholas T. UK management guidelines for erectile dysfunction. BMI 2000 321 499-503. 

Wagner G, Saenz de Tejada I. Update on male erectile dysfunction. BMI 1998 316 678-682. 

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