Erectile Dysfunction

Source: Lee M. Erectile Dysfunction. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th edition. http://accesspharmacy.com/content.aspx?aid=7994506. Accessed July 10, 2012.

Impotence

Failure to achieve penile erection suitable for sexual intercourse

Abnormality in system necessary for penile erection
- Organic erectile dysfunction (ED): Vascular, nervous, or hormonal systems—80% of patients
- Psychogenic ED: Psychological etiology

Interconnected sinuses in two corpora cavernosa in penis fill with blood to produce erection.
Acetylcholine works with other neurotransmitters (i.e., cyclic guanylate monophosphate, cyclic adenosine monophosphate, and vasoactive intestinal polypeptide) to produce penile arterial vasodilation and ultimately erection.
Organic ED associated with diseases that:
- Compromise vascular flow to corpora cavernosum (e.g., peripheral vascular disease, arteriosclerosis, and essential hypertension)
- Impair nerve conduction to brain (e.g., spinal cord injury and stroke)
- Impair peripheral nerve conduction (e.g., diabetes mellitus)
Secondary ED associated with hypogonadism.
Psychogenic ED associated with:
- Malaise
- Reactive depression
- Performance anxiety
- Sedation
- Alzheimer’s disease
- Hypothyroidism
- Mental disorders
Social habits (e.g., cigarette smoking and excessive ethanol intake) and medications (Table 1) can also cause ED

Table 1. Medication Classes that Can Cause Erectile Dysfunction

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Table 1. Medication Classes that Can Cause Erectile Dysfunction

Drug Class

Proposed Mechanism by Which Drug Causes Erectile Dysfunction

Special Notes

Anticholinergic agents (antihistamines, antiparkinsonian agents, tricyclic antidepressants, phenothiazines)

Anticholinergic activity

• Second-generation nonsedating antihistamines (e.g., loratadine, fexofenadine, or cetirizine) associated with less erectile dysfunction than first-generation agents

• Selective serotonin reuptake inhibitor (SSRI) antidepressants cause less erectile dysfunction than tricyclic antidepressants. Of SSRIs, paroxetine, sertraline, and fluoxetine cause erectile dysfunction more commonly than venlafaxine, nefazodone, trazodone, or mirtazapine.

• Phenothiazines with less anticholinergic effect (e.g., chlorpromazine) can be substituted in some patients if erectile dysfunction a problem

Dopamine antagonists (e.g., metoclopramide, phenothiazines)

Inhibit prolactin inhibitory factor, increasing prolactin levels

• Increased prolactin levels inhibit testicular testosterone production; depressed libido results

Estrogens, antiandrogens (e.g., luteinizing hormone–releasing hormone superagonists, digoxin, spironolactone, ketoconazole, cimetidine)

Suppress testosterone-mediated stimulation of libido

• With decreased libido, secondary erectile dysfunction develops because of diminished sexual drive

Central nervous system depressants (e.g., barbiturates, narcotics, benzodiazepines, short-term use of large doses of alcohol, anticonvulsants)

Suppress perception of psychogenic stimuli

Agents that decrease penile blood flow (e.g., diuretics, peripheral β-adrenergic antagonists, or central sympatholytics [methyldopa, clonidine, guanethidine])

Reduce arteriolar flow to corpora

• Any diuretic that produces significant decrease in intravascular volume can decrease penile arteriolar flow

• Safer antihypertensives include angiotensin-converting enzyme inhibitors, postsynaptic α1-adrenergic antagonists (terazosin, doxazosin), calcium channel blockers, and angiotensin II receptor antagonists

Miscellaneous

Unknown mechanism

• Finasteride, dutasteride

• Lithium carbonate

• Gemfibrozil

• Interferon

• Clofibrate

• Monoamine oxidase inhibitors

Data from Thomas A, Woodard C, Rovner ES, Wein AJ. Urologic complications of nonurologic medications. Urol Clin North Am 2003;30:123–131; and Lee M, Sharifi R. Sexual dysfunction in males. In: Tisdale JE, Miller DA, eds. Drug-Induced Diseases: Prevention, Detection, and Management. Bethesda, MD: ASHP, 2005:455–467.

Incidence increases as men age
Often associated with concurrent medical conditions
- Diabetes mellitus
- Hypertension—medications may contribute to ED
- Arteriosclerosis
- Hyperlipidemia
- Psychiatric disorders

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