Medical Conditions.-Any medical condition that can cause general debility has the potential to decrease sexual desire and performance. Pain, shortness of breath, angina, muscle weakness, or a CVA may be responsible for the dysfunction. The most common medical conditions associated with sexual difficulties are diabetes mellitus and hypertension, possibly because of the microvascular and neurovascular changes that are inherent in these conditions. In patients with diabetes, these factors may lead to a decrease in nerve stimulation and in nitric oxide generation. Some investigators have found hypogonadism to be commonly associated with diabetes mellitus. Poorly controlled plasma glucose levels add a separate risk factor, as does the presence of diabetic neuropathy. Not only is hypertension a separate risk factor for sexual problems but hypertension and diabetes often coexist in the patient. Generalized atherosclerosis and peripheral vascular disease may impede blood flow to the penis, as may a damaged vessel from pelvic injury or radiation therapy to the groin. Tobacco (cigarette smoking) can cause vascular insufficiency as well as a decrease in intrapenile nitric oxide levels. Excessive consumption of alcohol or use of other recreational drugs may cause sexual dysfunction, either by a direct effect on the penile neurovascular system or by causing increased prolactin or decreased testosterone production (or both). Peyronie's disease is a condition in which collagen tissue is converted to fibrous tissue, for unknown reasons; a palpable fibrous plaque created in the tunica albuginea causes bending of the penile shaft. The usual manifestation is a bend to one side during erection, which can occasionally be painful.

Drug-Related Causes.-Both prescription and over-the-counter medications have been shown to be the cause of erectile problems in as many as 25% of cases (Table 1). Although single medications can induce erectile dysfunction, the adverse medication effects are often additive. This situation is particularly frequent in older men who are taking multiple medications and in whom partial or complete erectile dysfunction often results. A psychologic component can make partial erectile dysfunction progress to complete erectile dysfunction. Some medications can affect libido, whereas others affect erectile function or ejaculation. Nonprescription medications, such as antihistamines or decongestants, may affect erectile function. Most psychotropic drugs can affect libido or erectile function, through either a direct action or an increased prolactin or a decreased testosterone level. Although antidepressants may cause dysfunction in susceptible patients, they may also be beneficial in improving libido in depressed men. Antihypertensive medications may cause erectile dysfunction either by drug-specific effects or by decreasing the systolic pressure and thereby decreasing the intracavernosal penile pressure. This result is especially prevalent in patients with diabetes or hypertension who have an underlying microvascular disease. Ketoconazole, aminoglutethimide, and similar drugs actually decrease the production of testosterone. Most of the earlier antihypertensive agents-such as reserpine, guanethidine, and hydralazine-caused sexual dysfunction. Some b-adrenergic blocking agents may cause sexual problems, but dysfunction with angiotensin-converting enzyme inhibitors or calcium channel blockers is less common. Some drugs (spironolactone, cimetidine, flutamide, or cyproterone acetate) may block the peripheral androgen receptors. Cimetidine may assume a greater importance because it can now be purchased without a prescription. Drugs such as a-methyldopa, spironolactone, digoxin, metoclopramide, and many psychotropic agents may raise prolactin levels. Thiazide diuretics, finasteride, anticholinergics, and pain medications cause dysfunction in a certain percentage of patients.