Male Sexual Dysfunction Other Causes

Other causes may affect one or more of the factors controlling the erectile mechanism. Because of the lack of scientific studies, however, their precise pathogenetic relationship remains speculative.

A. Drugs

Many drugs have been reported to cause ED, although the mechanism of action is largely unknown and there are few controlled studies on the sexual effects of a particular drug. In general, drugs that interfere with central neuroendocrine or local neurovascular control of penile smooth muscle have the potential to cause ED. Central neurotransmitter pathways, including serotonergic, noradrenergic, and dopaminergic pathways involved in sexual function, may be disturbed by antipsychotics, antidepressants, and centrally acting antihypertensive drugs.

Alpha-adrenergic blocking drugs, such as prazosin, terazosin, and doxazosin, may cause retrograde ejaculation owing to relaxation of the bladder neck. Beta-adrenergic blocking drugs may cause ED by potentiating α-1 adrenergic activity in the penis. Thiazide diuretics have been reported to cause ED, but the cause is unknown. Spironolactone can cause erectile failure as well as decrease in libido and gynecomastia.

Cigarette smoking may induce vasoconstriction and penile venous leakage because of its contractile effect on the cavernous smooth muscle. Alcohol in small amounts improves erection and increases libido because of its vasodilatory effect and the suppression of anxiety; however, large amounts can cause central sedation, decreased libido, and transient ED. Chronic alcoholism may cause hypogonadism and polyneuropathy, which may affect penile nerve function. Cimetidine, a histamine-H2 receptor antagonist, has been reported to decrease libido and cause erectile failure; it acts as an antiandrogen and can cause hyperprolactinemia. Other drugs known to cause ED are estrogens and drugs with antiandrogenic action, such as ketoconazole and cyproterone acetate.