Antiandrogens finasteride

Finasteride (5.58), a steroid-like enzyme inhibitor, represents an alternative approach to antiandrogens. Finasteride inhibits the 5a-reductase-catalyzed conversion of testosterone to DHT. In those tissues in which DHT is the active androgenic species (e.g., prostate), the androgenic stimulus is reduced in those tissues in which testosterone is the active androgenic species (e.g., muscle), the androgenic influence is minimally affected. 

Finasteride (Proscar) Antiandrogen Flecainide (T ambocor) Antiarrhythmic Fluconazole (Diflucan) Antifungal... 

B. Finasteride is a 5a-reductase inhibitor, which essentially makes dihydrotestosterone unavailable to the prostate but does not reduce serum testosterone levels. The decreased prostatic levels of dihydrotestosterone frequently result in a size regression of the prostate, while the relatively normal testosterone levels minimize a depressed libido. Flutamide and spironolactone exhibit antiandrogen effects by competing for the androgen receptor ketoconazole inhibits testosterone synthesis and stanozolol is an oral anabolic androgen preparation. 

Flutamide and bicalutamide are nonsteroidal antiandrogens available for use in conjunction with the gonadorelins (e.g. goserelin) in the treatment of prostatic carcinoma. Finasteride (p. 544), which inhibits conversion of testosterone to dihydrotestosterone, has localised antiandrogen activity in tissues where dihydrotestosterone is the principal androgen this makes it a useful drug in the treatment of benign prostatic hypertrophy. 

Antiandrogens Flutamide Bicalutamide Nilutamide Cyproterone acetate Progesterones 5-Of-Reductase inhibition Finasteride ... 

K., Parlow, A.F., Miller, D.D. and Dalton, J.T. (2004) Comparison of the pharmacological effects of a novel selective androgen receptor modulator, the 5a-reductase inhibitor finasteride, and the antiandrogen hydroxyflutamide in intact rats new approach for benign prostate hyperplasia. Endocrinology, 145, 5420-5428. 

C. 5a-Reductase Inhibitors Testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5a-reductase some tissues, most notably prostate cells and heur follicles, depend upon DHT rather than testosterone for androgenic stimulation. This enzyme is inhibited by finasteride, a drug used to treat benign prostatic hyperplasia and, at a lower dose, to prevent hair loss in men. Because the drug does not interfere with the action of testosterone, it is less likely than other antiandrogens to cause impotence, infertility, and loss of libido. 

Figure 1-15. Chemical structures of the active androgens, testosterone and DHT, some examples of antiandrogens, an estrogen, and finasteride.

The use of saw palmetto in BPH has continued as the main focus of numerous reports over the last decade. Such reports include in vivo experiments in animal models, in vitro experiments in prostate cells, and human clinical trials. The majority of these reports were in favor of saw palmetto s efficacy in improving lower urinary tract symptoms. Some studies showed that it favorably compared with finasteride and tamsulo-sin, the first-line treatments for There is no consensus yet on the mechanism of action of saw palmetto, but one or more of the following may be involved 5-a-reductase inhibition, indirect sympathomimetic effect (tti-adrenergic receptor binding), anti-inflammatory and/or hormonal antiandrogenic effects.2 2 3° 3i... 

One final area where steroids are used is as antiandrogens in the treatment of benign prostatic hyperplasia, prostate cancer and male hypersexuality. Dutasteride and finasteride (Fig. 20.34) are specific inhibitors of 5a-reductase, which is involved in the metabolism of testosterone. These two compounds are indicated for the treatment of benign prostatic hyperplasia, with finasteride also being indicated for male-pattern baldness. 

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