The Sexual Impotence
Until now we only enumerated a part of the means of the therapeutic arsenal with harmful action over the sexual behavior, as it results from the observations of the medical practice, but it is to assume that other medicines can have this kind of actions. Looking at the pathogenic mechanisms that determine, at some groups of medicines, an inhibitory action over the sexual behavior, only for some of them we have an explanation. It is known that in the adjustment mechanisms of the sexual behavior, a very important role has the existence of a certain balance of the vegetative nervous system sympathetic and parasympathetic. 
It is considered that a normal sexual behavior necessitates a certain balance and mutual conditioning between the cholinergic neuromediation (acetil-choline) on one side and the adrenergic and serotoninergic on the other side. A certain tonus of the noradrenergic neuromediation, adrenergic and serotoninergic is indispensable for accomplishing the sexual motion activity, in the presence of a cholinergic mediation tonus, of which depends trigger action of the sexual motivation.
Alternating to this balance, either through the net growth of the adrenergic tonus and serotoninergic, either through the net drop of the cholinergic tonus as well as the reverse situation, the net growth of the cholinergic tonus or the net drop of the adrenergic tonus and serotoninergic are factors that inhibit the sexual behavior.
This way we explain the inhibitory action over the sexual behavior of the central pympaticolitics (aldomet, reserpine, cataprasam) and peripheral (the alpha-blockers and beta-blockers) or of the parasimpatheticolitics (neuroleptics and tricycle antidepressants) or the anticholimergics (cimetidine). (two). In the case of the iatrogenic hyperprolactinemias induced by certain medicines, as well as in the lesional hyperprolactinemia from prolactinoma, it is known for sure that the excess of prolactine inhibits the sexual behavior, until the sexual impotence and also diminishes net the plasmatic testosterone and the spermatogenesis.
Stopping the medication that induces the hyperprolactinemia or correcting the pathological hyperprolactinemia (treatment with bromocriptine) determines a return to normal of the sexual behavior.
A therapy with anti-androgen hormones (estrogens, cyproteron acetate) or medicines with antiandrogenic action (digitalics, aldactone, aldactasine) determine hypogonadism and the inhibition of the sexual behavior, through the drop of the testosteronic level under the minimal level needed for erotizing the nervous central system. For some of the medicines stated before, it is not yet known the mechanism through which they inhibit the sexual behavior and are necessary supplementary studies for this purpose.
