The descriptions of the effects of ADEs on male sexual function are generally scarce and restricted to few topics. Any intervention which influences the sexual hormone system obviously also influences male sexual functions, e.g. antian-drogenic compounds, which depress sexual libido and other sexual functions. In some circumstances, it may be questionable as to whether the effect of a drug on male sexual functions is a desired therapeutic effect, or whether it is an untoward effect. For example, the depression of pituitary hormone secretion by the gonadotropin-releasing hormone (GnRH) analogues in the treatment of prostate carcinoma is important in order to achieve androgen deprivation and prolong the remission of the disease. On the other hand, the depression of gonadotropin secretion in these men by GnRH leads to impotence and infertility, which is definitely an untoward effect.
Some sexual ADEs which occur during treatment of other diseases are broadly recognized, e.g. erectile dysfunction as an ADE of p-blockers, which seems to be an unavoidable consequence of treating hypertension. It appears to be well explainable from the pathophysiology, although the clinical database is not so clear, as suggested in lay media. Other ADEs mentioned in the literature become clear only with expanded insight into the pharmacodynamics of the drug concerned, e.g. the unexpected antiandrogenic effect of ke-toconazole, an antifungal drug.
The ADEs on sexual functions are usually mild or moderate. They rarely prompt hospital admissions, which are classified as resulting from severe ADEs. This fact may explain why standard textbooks of pharmacology note sexual side effects of drugs only marginally. Entries of the 11 th edition (2005) of standard textbook Goodman & Gilman's Pharmacological Basis of Therapeutics can be quoted as examples of the unsatisfactory consequences of sexual side effects. Concerning the interaction of p-receptor antagonists with erectile function, which is considered an important cause of sexual dysfunction in elderly men, the textbook contains only two sentences: "The incidence of sexual dysfunction in men with hypertension who are treated with p-adrenoreceptor antagonists is not clearly defined. Although experience with the use of p-adrenoreceptor antagonists in pregnancy is increasing, information about the safety of those drugs during pregnancy is still limited [Widerhorn et al., 1987]". Specific serotonin reuptake inhibitors (SSRI), which delay ejaculation as an important sexual side effect, and thus are also used in the treatment of premature ejaculation, are considered also with only one sentence: "The SSRIs, as a group, have a high risk of nausea and vomiting, headache, and sexual dysfunction, including inhibited ejaculation in men and impaired orgasm in women." The chapter "Contraceptives" contains only 15 lines on the topic "Contraception, male". In the index, the entry "sexual function" is associated with the sub-entries "p-adrenoreceptor blockers, amylnitrite, androgens, antidepressants, antipsychotics, clonidine, cocaine, ethanol, gua-nandrel, PDE 5-inhibitors, phenoxylamin, phentolamin, prostaglandin, yohimbine". The entry "impotence" is associated with the sub-entries "p-adrenoreceptor blockers, alprostadil, ethanol, phentoalmin, PDE 5-inhibitors, prolactin, 5-a-reduc-tase inhibitors, thiazide, yohimbine". The entries "sperm" or "spermatogenesis" are not included.
The standard textbook of drug side effects, Meyler's side effects of drugs, in its 13th edition, contains a list of side effects on organs and systems, which includes "sexual functions" but not "fertility" (Dukes et al. 1996).
Although ADEs on sexual functions undoubtedly may impair the quality of life, it becomes evident that sexuality is among the less important spheres of quality of life. In a survey, all people interviewed (men, women, young people, elderly people) placed sexual life at position 25 of 25 life spheres concerning importance (Angermeyer et al. 2000).
Only a small number of drugs have been developed to improve male sexual health up to now, e.g. phosphodiesterase-5 inhibitors, in order to treat insufficient erectile function. These drugs compromise male sexual health owing to their adverse effects in other organ systems. As an example, the reports in the international press on heart attacks in patients using Viagra may be considered, which prompted many impotent patients to abstain from this drug. Today we know that Viagra, on the contrary, exerts favourable effects in coronary heart disease and pulmonary hypertension.
The description of sexual side effects of specific drugs, however, does not allow definitive statements on the cause of sexual dysfunction by drugs in a individual patient. There are only a few published articles which report the incidence of drug use in patients with sexual dysfunction. They describe the frequency with which men with erectile dysfunction use a drug and the extent of sexual dysfunction. The Massachusetts Male Aging Study conducted by the New England Research Institute identified a number of drugs used in ageing men for different purposes, which was associated with sexual dysfunction, but the question remained unanswered as to whether these associations are independent of the underlying health conditions (Derby et al. 2001). The answer to this question is complex and may be facilitated by a comprehensive database on sexual side effects of distinct drugs.
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