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PubMed2006

Dutasteride improves objective and subjective disease measures in men with benign prostatic hyperplasia and modest or severe prostate enlargement.

PURPOSE: We determined whether the effect of dutasteride for benign prostatic hyperplasia is influenced by baseline prostate volume using data from 3 phase III clinical trials. MATERIALS AND METHODS: Patients randomized to dutasteride or placebo in the double-blind portion of the phase III studies were eligible to receive 0.5 mg dutasteride daily in a 2-year open label extension in dutasteride/dutasteride and placebo/dutasteride groups. Patients were prospectively stratified according to baseline prostate volume 30 to less than 40 and 40 cc or greater. RESULTS: In patients treated with dutasteride throughout the study (dutasteride/dutasteride group) the mean reduction in prostate volume from baseline to month 48 was 30.3% in those with a baseline prostate volume of 30 to less than 40 cc and 26.2% in those with a prostate volume of 40 cc or greater. Mean improvements in peak urinary flow from baseline to month 48 were 2.7 ml per second regardless of baseline prostate volume. Improvements in the American Urological Association symptom index score were 6.3 in men with a prostate volume of 30 to less than 40 cc and 6.5 in those with a prostate volume of 40 cc or greater. No significant relationships between treatment effect and baseline prostate volume were observed for these parameters. In dutasteride/dutasteride treated patients the risk of acute urinary retention was decreased by 60% in those with a prostate volume of 30 to less than 40 cc and 55% in those with a prostate volume of 40 cc or greater vs values in placebo/dutasteride treated patients (p = 0.036 and <0.001, respectively). The corresponding values for benign prostatic hyperplasia related surgery were 27% and 48% (p = 0.35 and <0.001, respectively). CONCLUSIONS: This analysis demonstrates that dutasteride significantly improves objective (prostate volume and peak urinary flow) and subjective (symptom scores) measures even in patients with only a slightly enlarged prostate (30 to less than 40 cc). The risks of acute urinary retention and benign prostatic hyperplasia related surgery were decreased regardless of baseline prostate volume.

Aged↗
PubMed2006

Actions of 5alpha-reductase inhibitors on the epididymis.

Testosterone is converted to the more biologically active androgen, dihydrotestosterone (DHT), by steroid 5alpha-reductase. Two isozymes of 5alpha-reductase, types 1 and 2, are abundantly expressed in the epididymis. DHT is the androgen found in the nuclei of epididymal cells and is essential for the maturation of spermatozoa. Thus, one approach to block androgen action in the epididymis is to inhibit DHT formation. Several compounds have been reported to inhibit either one or both forms of 5alpha-reductase in many tissues. The first commercially available inhibitor of 5alpha-reductase, finasteride, has a predominant effect on the type 2 isozyme, while more recently developed agents, such as dutasteride, PNU157706 and FK143, act as dual inhibitors. We found that the treatment of adult rats with such agents results in pronounced effects on the expression of genes essential to the formation of the optimal luminal microenvironment that is required for proper sperm maturation. Furthermore, drug treatment caused a significant decrease in the percentage of progressively motile and morphologically normal spermatozoa in the cauda epididymides. Mating females to treated males resulted in fewer successful pregnancies and a higher rate of pre-implantation loss. Thus, there may be a role for dual 5alpha-reductase inhibitors as potential components of a male contraceptive.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed2006

Steroid requirements for regulation of the alpha4 subunit of the GABA(A) receptor in an in vitro model.

The alpha4 subunit of the GABA(A) receptor (GABAR) has relatively low expression in the CNS, but is increased in vivo following 48 h administration of the GABA-modulatory steroid 3alpha-OH-5alpha[beta]-pregnan-20-one (THP or [allo]pregnanolone) to female rats. The purpose of the following study was to determine the optimal conditions for steroid-induced upregulation of alpha4 expression in an in vitro model. To this end, we used the IMR-32 cell, a neuroblastoma cell line, which normally expresses alpha4 mRNA at low levels. In undifferentiated IMR-32 cells, 48 h administration of THP increased alpha4 expression when ambient THP levels were reduced by the 5alpha-reductase blocker 4MA, suggesting that the background steroid milieu affects steroid regulation of this subunit. Following neuronal differentiation in serum-free medium, 48 h THP treatment significantly increased alpha4 expression two-fold following application of nerve growth factor (NGF) suggesting that development of neuronal processes facilitates this effect of the steroid. In the absence of NGF treatment, combined administration of 17beta-estradiol (E2) plus THP also increased alpha4 expression to a similar extent as THP following NGF treatment. In addition, E2 alone effectively increased alpha4 expression to maximal levels following NGF treatment. In contrast, neuronal differentiation in the absence of serum deprivation did not increase alpha4 levels. These results suggest that both THP and E2 can increase expression of the GABAR alpha4 subunit, but that this effect is dependent upon the background steroid milieu as well as the degree of neuronal development. These findings demonstrate optimal conditions for steroid-induced upregulation of the alpha4 subunit in an in vitro system.

Analysis of Variance↗
PubMed2004

In vitro antigenotoxic potential of acitretin in human lymphocytes treated with the antineoplastic alkylating agent ASE (NSC-71964).

Acitretin is widely used in the systemic treatment of severe forms of psoriasis and other skin disorders. ASE, namely 3beta-hydroxy-13alpha-amino-13,17-seco-5alpha-androstan-17-oic-13,17-lactam-p-bis(2-chloro-ethyl)amino phenylacetate (AzaSteroidalEster, NSC-71964), is an alkylating agent with antineoplastic activity and mutagenic properties. The aim of this study was to investigate the possible genotoxic and/or antigenotoxic effects of acitretin in human lymphocyte cultures in vitro, using sister chromatid exchange (SCE) and cytokinesis-blocked micronucleus (CBMN) assays. Micronucleus (MN) analysis was achieved in combination with fluorescence in situ hybridization (FISH), using an alpha-satellite DNA pancentromeric probe. It was found that acitretin alone demonstrated no clastogenic or aneugenic activity. However, simultaneous incubation of lymphocyte cultures with ASE and acitretin resulted in a reduction of ASE-induced SCEs. For MN analysis lymphocytes were treated with ASE and acitretin at 21 and 41 h after culture initiation, corresponding to G1 and G2 phases, respectively, and lasted until cell harvest. Acitretin caused a decrease in ASE-induced MN when treatment of cells started at 41 h, but exerted no effect on them when treatment started at 21 h. These findings suggest that acitretin exerts antigenotoxic effects in human lymphocyte cultures, the expression of which may be related to the cycle phase of the cells upon onset and duration of the treatment, at least as far as MN frequency is concerned.

Acitretin↗
PubMed2005

Variability of alkaloids in the skin secretion of the European fire salamander (Salamandra salamadra terrestris).

The two major alkaloids, samandarine and samandarone, were identified in the skin secretion of individual specimens from two populations of the European fire salamander (Salamandra salamandra terrestris) by gas chromatography/mass spectrometry. High intraspecific variability in the ratio of both alkaloids was observed, but also in individual specimens over a period of 4 months suggesting separate metabolic pathways of the compounds. Alkaloid synthesis appears to take place also in liver, testes and ovaries, whereas the larvae of the salamanders are entirely free of alkaloids.

Alkaloids↗
PubMed2004

Efficacy and safety of dutasteride in the four-year treatment of men with benign prostatic hyperplasia.

OBJECTIVES: To assess the long-term safety and efficacy of dutasteride, a dual type 1 and type 2 5-alpha-reductase inhibitor, in the treatment of symptomatic benign prostatic hyperplasia and associated lower urinary tract symptoms. METHODS: Data from two Phase IIIa multicenter, randomized, placebo-controlled trials of 2-year duration plus a 2-year open-label extension were pooled and analyzed. The entry criteria included age 50 years old or older, clinical diagnosis of benign prostatic hyperplasia, prostate volume of 30 cm3 or greater, American Urological Association symptom score of 12 or greater, peak urinary flow rate of 15 mL/s or less, and prostate-specific antigen level of 1.5 ng/mL or greater but less than 10 ng/mL. RESULTS: A total of 2802 men were randomized into the double-blind phase of the two studies with 1908 patients (68%) completing the study. Of these, 1570 subjects were enrolled in the open-label phase, and 569 subjects received dutasteride for 48 months. Changes at the 48-month visit for dutasteride/dutasteride-treated subjects included improvement in prostate volume (-26.2%), American Urological Association Symptom Index (-6.1 points), and peak urinary flow rate (+2.8 mL/s). Changes for the placebo/dutasteride group included prostate volume (-20.7%), American Urological Association Symptom Index (-5.3 points), and peak urinary flow rate (+1.8 mL/s). Acute urinary retention and surgery occurred in a small percentage of subjects (less than 2% and less than 1%) in the open-label extension phase. Dutasteride was well tolerated with no statistically significant increase in drug-related adverse events during the open-label extension and no adverse laboratory trends. CONCLUSIONS: Dual inhibition of 5-alpha-reductase with dutasteride provided sustained efficacy in subjects with symptomatic benign prostatic hyperplasia treated for 48 months. Near-complete, long-term suppression of dihydrotestosterone (93% at 48 months) with dutasteride did not lead to an increase in adverse events compared with that reported in the 2-year period.

5-alpha Reductase Inhibitors↗
PubMed2004

Effect of dutasteride on the detection of prostate cancer in men with benign prostatic hyperplasia.

OBJECTIVES: To examine the rate of prostate cancer detection in three large randomized placebo-controlled benign prostatic hyperplasia trials of dutasteride. Dutasteride, which lowers serum dihydrotestosterone more than 93% by inhibiting type 1 and type 2 5-alpha-reductase, is effective in the treatment of benign prostatic hyperplasia. However, its effect on the development of prostate cancer is unknown. METHODS: A total of 4325 men with benign prostatic hyperplasia but without a history, or evidence, of prostate cancer, and a serum prostate-specific antigen level of 1.5 to 10 ng/mL, were randomized to 0.5 mg/day dutasteride or placebo for 24 months. The prostate cancer detection rates for subjects were determined by non-protocol-mandated biopsies, either during the double-blind phase of the study or during the first 3 months of the open-label extension. A follow-up questionnaire was administered to a subset of consenting subjects to ascertain the number, outcomes, and reasons for the prostate biopsies. RESULTS: The cumulative incidence of prostate cancer as an adverse event was significantly lower in the dutasteride versus placebo group at 24 months (1.1% versus 1.9%, P = 0.025) and 27 months (1.2% versus 2.5%, P = 0.002). There were no differences in the diagnosis rates of prostate cancer during the first 15 months, after which time the detection rate of prostate cancer increased in the placebo group and remained low in the dutasteride group. CONCLUSIONS: Prostate cancer detection was significantly lower in subjects randomized to dutasteride compared with the placebo group. These results have prompted the initiation of the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) study, which was designed and powered to test the hypothesis that treatment with dutasteride decreases the incidence and progression of prostate cancer.

5-alpha Reductase Inhibitors↗
PubMed2005

The dual 5-alpha-reductase inhibitor dutasteride induces atrophic changes and decreases relative cancer volume in human prostate.

OBJECTIVES: To perform the first evaluation of the effects of the 5-alpha-reductase inhibitor class of drugs on cancer histopathologic features at radical prostatectomy in a placebo-controlled multicenter trial. METHODS: We analyzed prostatectomy slides in a blinded manner from 17 men treated with dutasteride, an inhibitor of types 1 and 2 isoenzymes of 5-alpha-reductase, and 18 men treated with placebo for 5 to 11 weeks before radical prostatectomy. The histopathologic features of benign epithelium, high-grade prostatic intraepithelial neoplasia, and cancer were recorded, and the treatment effect was scored. Digital imaging analysis was used to measure the stroma/epithelium ratio and epithelial height, as well as the nuclear area in cancer. RESULTS: In benign epithelium, treatment caused distinctive cytoarchitectural changes of atrophy and a decrease in the epithelial height (P = 0.053). The peripheral zone showed the most marked response to treatment. In cancer tissue, the tumor volume was significantly lower in the dutasteride-treated men than in the placebo-treated men (mean 15% versus 24%, respectively, P = 0.025), the percentage of atrophic epithelium was increased (P = 0.041), and the stroma/gland ratio was doubled (P = 0.046). The treatment alteration effect score was doubled (P = 0.055) and did not correlate with any Gleason score changes. CONCLUSIONS: After short-term dutasteride treatment, benign epithelium showed involution and epithelial shrinkage, and prostate cancer tissue demonstrated a decrease in epithelium relative to stroma. These findings indicate that dutasteride induces significant phenotypic alterations in both the benign and the neoplastic prostate, supportive of a chemopreventive or chemoactive role.

5-alpha Reductase Inhibitors↗
PubMed2006

Development of nomogram to predict acute urinary retention or surgical intervention, with or without dutasteride therapy, in men with benign prostatic hyperplasia.

OBJECTIVES: To develop a prediction model, or nomogram, that would predict the probability that a man with benign prostatic hyperplasia would experience acute urinary retention (AUR) or require surgical intervention (SI) within 2 years, with or without dutasteride therapy. METHODS: We modeled 4294 men treated in the Phase III dutasteride benign prostatic hyperplasia trials. These men were characterized at baseline by a number of parameters, including the American Urological Association Symptom Index, Benign Prostatic Hyperplasia Impact Index questionnaire, prior use of selective alpha1-blockers, prostate volume, prostate-specific antigen level, and maximal flow rate. Cox proportional hazards regression analysis was used to relate these baseline variables to their future probability of AUR/SI within 2 years. The nomogram was internally validated with bootstrapping to assess its discrimination and calibration. Discrimination was quantified as the concordance index. RESULTS: The nomogram appeared to be accurately calibrated and discriminating (concordance index 0.71, P <0.001). CONCLUSIONS: We constructed a nomogram for predicting the probability that a man would experience AUR or require SI within 2 years of benign prostatic hyperplasia diagnosis. At 24 months of follow-up, 7.4% of placebo patients and 3.7% of dutasteride patients had experienced AUR and/or SI, representing a 50% relative risk reduction and a 3.7% absolute risk reduction. For the greatest risk patient randomized to the Phase III dutasteride trial, the nomogram predicted a maximal risk of 27%, significantly greater than the median risk of the placebo-treated patients.

Acute Disease↗
PubMed2006

Efficacy of neoadjuvant bicalutamide and dutasteride as a cytoreductive regimen before prostate brachytherapy.

OBJECTIVES: To evaluate the cytoreductive effectiveness of combined neoadjuvant bicalutamide and dutasteride before prostate brachytherapy for clinically localized prostate cancer. METHODS: From April 2003 to May 2005, 31 patients opted for cytoreduction with bicalutamide (50 mg daily) and dutasteride (0.5 mg daily). Before, and at 3 months (90 +/- 5 days) after, the initiation of medical therapy, all patients underwent a transrectal ultrasound volumetric study of the prostate gland, with ellipsoid volume determination of the prostate gland and transition zone. The variables analyzed included pretreatment and posttreatment prostate and transition zone volumes and changes in width, height, and length of the prostate gland and transition zone. A multivariate analysis was performed to identify predictors for prostate gland and transition zone volume reduction. RESULTS: Before the initiation of bicalutamide and dutasteride, the mean prostate volume was 54.3 cm3 by planimetric summation and 49.7 cm3 by ellipsoid volume calculation. After a 3-month course of combination medical therapy, the average prostate volume was 36.1 cm3 (33.6% reduction) and 32.5 cm3 (34.6% reduction) using the volumetric and ellipsoid volume determinations, respectively. Bicalutamide and dutasteride resulted in a 39.8% reduction in transition zone volume (20.8 cm3 versus 12.4 cm3). The prostate gland and transition zone dimensions (width, height, and length) decreased about 11.4% to 19.9%. CONCLUSIONS: The prostate gland and transition zone volume reductions after a 3-month course of neoadjuvant bicalutamide and dutasteride are comparable to previous reports of volume reduction using a luteinizing hormone-releasing hormone agonist with or without an antiandrogen.

5-alpha Reductase Inhibitors↗
PubMed2004

[Use of 5-alpha-reductase inhibitors in the prevention of prostate cancer].

5-alpha-reductase inhibitors are now in widespread use for the treatment of benign prostatic hyperplasia (BHP) and these molecules have recently come under the spotlight in prostate cancer. Their peripheral "hormonal" action inducing reduced intraprostatic DHT synthesis seems to involve them in this hormone-dependant disorder. Finasteride evaluated in the treatment of BPH (PLESS study) was found to have a preventive effect on the incidence of cancer and this activity was assessed in a specific trial (PCPT study). Nevertheless, in the latter randomized study with a 7-year follow-up period, a reduction in the global incidence of the number of cases of cancers was associated with an increase in the number of high-grade cancers. A slight reduction in prostate cancer was also noted in the studies with dutasteride in BPH (ARIA3001, ARIA3002 and ARIB3003). An international multicenter study (REDUCE) is currently being conducted to confirm the preventive value of this molecule which has a more complete activity than finasteride with its inhibitory action on the two 5-alpha-reductase iso-enzymes, and may therefore have a clearer efficiency and rule out the risk of onset of high-grade cancer.

Aged↗
PubMed2004

[Dutasteride: main results in the treatment of benign prostatic hyperplasia].

Benign prostatic hyperplasia (BPH) is a progressive disease characterized by an increase in prostatic volume. The resulting urinary irritative and/or obstructive symptoms, when present, often reduce the patient's quality of life. Prostatic dihydrotestosterone, the androgen produced following transformation of testosterone by the enzyme 5-alpha-reductase, is responsible for these changes. Among various products used for drug therapy, 5-alpha-reductase inhibitors play a specific role in the long-term management of BPH. Between the two currently available products, dutasteride is the only dual 5-alpha-reductase inhibitor (types 1 and 2). The efficacy of dutasteride was tested in several scientific studies and the cumulative results of three controlled, double-blind pivotal studies, showed at 2-year a clear improvement in all parameters modified during this disorder. A significant decrease in the severity and frequency of the urinary symptoms, in prostate volume, the risk of urine retention, the necessity to resort to surgery and an increase in peak urinary flow were observed with dutasteride. These results were confirmed in the 4-year-open label extension of these pivot studies both for tolerability of the product and the maintenance of its efficacy over time.

Azasteroids↗
PubMed1987

The inhibition of 3 beta HSD activity in porcine granulosa cells by 4-MA, a potent 5 alpha-reductase inhibitor.

Addition of 17 beta-N,N,-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstane-3-one, a potent 5 alpha-reductase inhibitor, to granulosa cell cultures inhibited the FSH-stimulated progesterone synthesis during both the initial 48 h induction period and the subsequent 6h test period in a dose-dependent fashion. Besides being a more potent inhibitor of FSH-stimulated progesterone synthesis than testosterone, 4-MA also synergized with the androgen to inhibit progesterone synthesis. These results indicate that 4-MA has a direct inhibitory action on 3 beta-HSD.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Pharmacokinetic parameters and mechanisms of inhibition of rat type 1 and 2 steroid 5alpha-reductases: determinants for different in vivo activities of GI198745 and finasteride in the rat.

The interaction of baculovirus expressed rat steroid 5alpha-reductase types 1 and 2 (r5AR1 and r5AR2) with 17beta-N-(2,5-bis(trifluoromethyl)phenyl)carbamoyl-4-aza-5alpha-androst-1-en-3-one (GI198745) was investigated at pH 7 and 37 degrees. This 5alpha-reductase inhibitor was found previously to be a time-dependent inhibitor of the two human 5alpha-reductase isozymes. In contrast, we demonstrate in the present study that although GI198745 is a potent time-dependent inhibitor of r5AR2, it is a classical rapid-equilibrium inhibitor of r5AR1. This type of behavior with human and rat 5alpha-reductases has been shown for the inhibitor 17beta-(N-tert-butylcarbamoyl)-4-aza-5alpha-androst-1-en-3-one (finasteride), a current therapy for benign prostatic hyperplasia. Inhibition of r5AR1 by GI198745 was competitive with testosterone and followed Michaelis-Menten kinetics with a K(i) value of 0.3 +/- 0.02 nM. Data for the inhibition of r5AR2 by GI198745 were consistent with a two-step mechanism, where K(i) is the dissociation constant for an initial enzyme-inhibitor complex and k(3) is the rate constant for the second slow step. The pseudo-bimolecular rate constant (k(3)/K(i)) for the association of GI198745 with r5AR2 was (2.0 +/- 0.4) x 10(7) M(-1) sec(-1). The high affinity of this inhibitor for r5AR2 was further demonstrated by the inability of the enzyme-inhibitor complex to dissociate after approximately 7 days of dialysis at 4 degrees. Both GI198745 and finasteride appear to inactivate r5AR2 by apparent irreversible modification, but are classical, reversible inhibitors of r5AR1. Therefore, we hypothesize that because of its pharmacokinetic parameters and increased potency against r5AR1, GI198745 is more effective than finasteride in preventing the growth of the rat prostate.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1999

Interaction of anisatin with rat brain gamma-aminobutyric acidA receptors: allosteric modulation by competitive antagonists.

Anisatin, a toxic sesquiterpene isolated from the Japanese star anise (Illicium anisatum L.), competitively inhibited the specific binding of [3H]4'-ethynyl-4-n-propylbicycloorthobenzoate ([3H]EBOB), a non-competitive antagonist of gamma-aminobutyric acid (GABA)A receptors, to rat brain membranes with an IC50 value of 0.43 microM. R 5135, a competitive GABA antagonist, decreased the potency of anisatin in inhibiting [3H]EBOB binding in a negatively cooperative manner. Two other competitive antagonists, SR 95531 (gabazine) and (-)-bicuculline methiodide, had similar effects. On the other hand, R 5135 exerted little influence on the potencies of the other non-competitive antagonists tested: EBOB, picrotoxinin, isopropylbicyclophosphate, and dieldrin. Thus, anisatin was clearly different from the other non-competitive antagonists in responding to the action of competitive antagonists on (GABA)A receptors. These findings suggest that the binding region of anisatin might overlap with that of the other non-competitive antagonists, but that anisatin must interact with other specific region(s).

Affinity Labels↗
PubMed1998

A model for the turnover of dihydrotestosterone in the presence of the irreversible 5 alpha-reductase inhibitors GI198745 and finasteride.

OBJECTIVE: To develop a pharmacokinetic-pharmacodynamic model that characterizes the conversion of testosterone to dihydrotestosterone (DHT) by 5 alpha-reductase types 1 and 2 and the irreversible inhibition of 5 alpha-reductase by finasteride, a 5 alpha-reductase type 2 inhibitor and by GI198745 (dutasteride), a potent and specific dual 5 alpha-reductase inhibitor. METHODS: Healthy men (n = 48) received doses of 0.1 to 40 mg GI198745 (n = 4 subjects per dose), 5 mg finasteride (n = 8), or placebo (n = 8) in a parallel-group study. Plasma concentrations of GI198745, finasteride, and DHT were measured frequently up to 8 weeks after dosing. Models were fitted with mixed-effects modeling with the NONMEM program. RESULTS: The pharmacodynamics were well described with a model that accounted for the rates of DHT formation and elimination, 5 alpha-reductase turnover, relative capacity of the 2 5 alpha-reductase isozymes, and the rates of irreversible inhibition of one (finasteride) or both (GI198745) types of 5 alpha-reductase. The model indicated that type 2 5 alpha-reductase contributed approximately 80% of plasma DHT. GI198745 was about 3-fold more potent than finasteride on 5 alpha-reductase type 2. Nearly full blockade of both isozymes was achieved at doses of 10 mg or more GI198745, although the potency of this agent on 5 alpha-reductase type 1 was less than on type 2. CONCLUSIONS: A physiologically based model for the turnover and irreversible inhibition of 5 alpha-reductase and for formation and elimination of DHT described the data well. This model helps explain differences in the rates of onset and offset of effect and offers a way to determine the relative potency of the irreversible 5 alpha-reductase inhibitors.

5-alpha Reductase Inhibitors↗
PubMed1983

12. Androgens: Pharmacodynamics and antagonists. Biochemical and biological studies with 4-aza-steroidal 5 alpha-reductase inhibitors.

A series of 4-aza-3-oxosteroids were found to be good inhibitors of steroid 5 alpha-reductase. Two of these compounds. 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (4-MA) and 4-methyl-4-aza-5 alpha-pregnan-3-one-20(s)-carboxylate, inhibit 5 alpha-reductase competitively with testosterone (T) with Ki values of 5 and 1.7 nM, respectively. These 5 alpha-reductase inhibitors also have an affinity to the androgen receptor which is orders of magnitude lower than that of 5 alpha-dihydrotestosterone (DHT), spironolactone and cyproterone acetate. 4-MA decreases the prostatic concentration of DHT and increases that of T in intact male rats and in castrates given T or its propionate derivative. 4-MA is a better inhibitor of T-induced growth than of DHT-induced growth of the prostate and seminal vesicles in castrated rats. It decreases the weight of the prostate and seminal vesicles in intact rats and that of the prostate in dogs. It has no significant antifertility activity in rats. In pregnant rats, 4-MA reduces the ano-genital distance of male fetuses. 4-MA has no significant androgenic, estrogenic, progestational, antiprogestational or antigonadotrophic activity.

5-alpha Reductase Inhibitors↗