Medical brain notes 47

  Drugs Used in the Treatment  of Erectile Dysfunction The term impotence has been used to indicate the inability of the male to attain and maintain erection of the penis sufficient to permit satisfactory sexual inter-course. Erectile dysfunction (ED) is the preferred term. ED is a common problem, especially among older men. Perhaps a more precise term for ED is that used to sig-nify inability of the man to achieve an erect penis as part of the multifaceted process of male sexual func-tion. Overall, the process encompasses a variety of physical aspects with significant psychological and be-havioral components.   In the United States approximately 10 million men have ED. While erectile function may not be the most important indicator of sexual satisfaction, ED may con-tribute to mental stress that affects interactions with family and associates. While many advances have oc-curred in the diagnosis and treatment of ED, other aspects remain poorly understood by the general po...

  PHYSIOLOGY OF PENILE ERECTION   The physiology of penile erection involves an interplay of anatomical, hemodynamic, neurophysiological, and sex hormone interaction. Penile erection is the result of a complex interaction between the central nervous sys-tem and other local factors. This physical event also can be influenced by psychological factors.   The penis is mainly supplied by the internal puden-dal artery, and three major sets of veins, superficial, in-termediate, and deep veins, drain it. Drug-induced changes in neurotransmitter action can affect local blood flow. Vascular supply, intrinsic smooth muscles of the penis, and adjacent striated muscles are controlled by nerves arising from the thoracolumbar sympathetic, the lumbosacral parasympathetic, and the lumbosacral somatic systems. The pudendal nerve is the major so-matic pathway innervating the male genitalia.   In addition to the integrated participation of the pe-ripheral nerves, central neural pathways...

  INDIVIDUAL AGENTS   The pharmacological agents useful in this disorder may be grouped under five broad categories of treatment (Table 64.2). Such a classification system takes into ac-count the mode of drug action, the route of administra-tion, and the means by which target organ selectivity is achieved.   Oral medication for treatment of ED is relatively new. Earlier measures often employed the intracaver nosal injection of a vasoactive agent or a systemic mode of drug administration.   Local injections or dermal ap-plications were frequently required for satisfactory pharmacological actions upon the vascular smooth mus-cles of the penis. Compounds with relatively short dura-tion of action were found to be less than satisfactory in maintaining penile erections.   Combinations of drugs have sometimes been used to take advantage of the differing onset and duration of action of the individual compounds. A rapid onset of ac-tion and a sufficient duration are impo...