Protective role of hesperidin in finasteride-induced testicular toxicity in adult male Wistar rats: Insights into oxidative stress, apoptosis, and ultrastructure of seminiferous tubules

A negative impact of finasteride on fertility has been reported, in which over production of reactive oxygen species and apoptosis were implicated. Hesperidin, a plant-derived bioflavonoid with antioxidant and anti-apoptotic effects, may mitigate these adverse effects. In order to investigate the possible protective role of hesperidin against finasteride-induced seminiferous tubules toxicity in adult male Wistar rats, 60 rats were randomized into five groups (I-V) receiving distilled water, 0.5% sodium carboxymethylcellulose solution, hesperidin, finasteride, and combined hesperidin and finasteride respectively. Testicular weight, sperm count and motility were determined. Testicular tissue homogenates were prepared to measure the level of malondialdehyde (MDA), total antioxidant capacity (TAC), reduced glutathione (GSH) and the gene expression of caspase-3 and B-cell lymphoma 2 (Bcl2). Testes were processed for light and electron microscopic evaluation. Johnsen score was calculated. Administration of finasteride resulted in significantly decreased testicular weights, sperm count and motility, Johnsen score, tissue levels of TAC and GSH together with significant increase in tissue MDA. Gene expression revealed significantly increased caspase-3 and decreased Bcl2. Furthermore, finasteride disrupted the seminiferous tubules, causing degenerative changes affecting Sertoli cells and spermatogenic cells. Co-administration of hesperidin with finasteride resulted in improvement in testicular weights, TAC, GSH, Bcl2, Johnsen score, sperm count and motility as well as preservation of the structure of the seminiferous tubules. To conclude, hesperidin was found to have a protective potential on finasteride-induced oxidative stress, apoptosis and testicular structural damage.

A Systematic Review of Topical Finasteride in the Treatment of Androgenetic Alopecia in Men and Women

INTRODUCTION

Currently, only topical minoxidil (MNX) and oral finasteride (FNS) are approved by the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of androgenetic alopecia. Although FNS is efficacious for hair regrowth, its systemic use is associated with side effects limiting long-term utilization. Exploring topical FNS as an alternative treatment regimen may prove promising.

METHODS

A search was conducted to identify studies regarding human in vivo topical FNS treatment efficacy including clinically relevant case reports, randomized controlled trials (RCTs), and prospective studies.

RESULTS

Seven articles were included in this systematic review. In all studies, there was significant decrease in the rate of hair loss, increase in total and terminal hair counts, and positive hair growth assessment with topical FNS. Both scalp and plasma DHT significantly decreased with application of topical FNS; no changes in serum testosterone were noted.

CONCLUSION

Preliminary results on the use of topical FNS are limited, but safe and promising. Continued research into drug-delivery, ideal topical concentration and application frequency, side effects, and use for other alopecias will help to elucidate the full extent of topical FNS' use. <p><em>J Drugs Dermatol. 2018;17(4):457-463.</em></p>.

Production of biologically active oxidized derivatives of finasteride through metabolism by Aspergillus niger culture

CONTEXT

Among the 4-azasteroids, finasteride is biologically the most important compound having preventive effect against male pattern baldness (MPH) and benign prostatic hyperplasia commonly called enlargement of prostate gland.

OBJECTIVE

The microbial transformation of finasteride by fungus Aspergillus niger (ATCC 10549) has been investigated to obtain biologically more potent derivatives.

MATERIALS AND METHODS

Fermentation of finasteride was performed with filamentous fungus Aspergillus niger (ATCC 10549). This transformation resulted in the production of two transformed products, which were purified through column chromatography. In vitro lipoxygenase inhibitory potential was determined by incubating 20 mL of the enzyme with 10 mL of test sample (100 μM) in 0.1 mM (pH 7.0) phosphate buffer for 5 min at 258 °C followed by addition of 10 μL of substrate (linolenic acid) to reaction mixture and measuring the formation of complex spectrophotometrically.

RESULTS

Structure elucidation of biotransformed metabolites was ascertained through extensive 1D and 2D spectroscopic techniques. This study established the fact that A. niger promoted stereospecific dihydroxylation at C-11 and C-15 of finasteride. The resulting biotransformed metabolites were characterized as 11α-hydroxyfinasteride and 15β-hydroxyfinasteride, respectively. Finasteride along with transformed metabolites were analyzed for their in vitro lipoxygenase (LOX) inhibition assay. Among the tested compounds 15β-hydroxyfinasteride showed good activity with IC₅₀ value 112.56 ± 2.23 μM while inhibitory effect in case of 11α-hydroxyfinasteride was low with IC₅₀ value 186.05 ± 1.34 μM. Standard compound baicalein revealed IC₅₀ value being 22.0 ± 0.05 μM.

CONCLUSION

The present investigation highlighted the fact that potentially active compound can be produced through the technology of biotransformation.

Equine 5α-reductase activity and expression in epididymis

The 5α-reductase enzymes play an important role during male sexual differentiation, and in pregnant females, especially equine species where maintenance relies on 5α-reduced progesterone, 5α-dihydroprogesterone (DHP). Epididymis expresses 5α-reductases but was not studied elaborately in horses. Epididymis from younger and older postpubertal stallions was divided into caput, corpus and cauda and examined for 5α-reductase activity and expression of type 1 and 2 isoforms by quantitative real-time polymerase chain reaction (qPCR). Metabolism of progesterone and testosterone to DHP and dihydrotestosterone (DHT), respectively, by epididymal microsomal protein was examined by thin-layer chromatography and verified by liquid chromatography tandem mass spectrometry (LC-MS/MS). Relative inhibitory potencies of finasteride and dutasteride toward equine 5α-reductase activity were investigated. Pregnenolone was investigated as an additional potential substrate for 5α-reductase, suggested previously from in vivo studies in mares but never directly examined. No regional gradient of 5α-reductase expression was observed by either enzyme activity or transcript analysis. Results of PCR experiments suggested that type 1 isoform predominates in equine epididymis. Primers for the type 2 isoform were unable to amplify product from any samples examined. Progesterone and testosterone were readily reduced to DHP and DHT, and activity was effectively inhibited by both inhibitors. Using epididymis as an enzyme source, no experimental evidence was obtained supporting the notion that pregnenolone could be directly metabolized by equine 5α-reductases as has been suggested by previous investigators speculating on alternative metabolic pathways leading to DHP synthesis in placenta during equine pregnancies.

Finasteride, not tamsulosin, increases severity of erectile dysfunction and decreases testosterone levels in men with benign prostatic hyperplasia

BACKGROUND

5α-reductase inhibitors (5α-RIs) (finasteride and dutasteride) have been proven useful in treatment of lower urinary tract symptoms (LUTS) related to benign prostatic hyperplasia (BPH). However, these inhibitors exert undesirable sexual side effects and, in some cases, these effects are persistent. There is considerable disagreement with regard to whether the adverse side effects resolve with continuous treatment.

AIM

To investigate the long-term adverse effects of finasteride treatment in men with BPH on erectile function and to compare these adverse effects in men treated with the α1-adrenergic receptor blocker, tamsolusin.

METHODS

In this retrospective registry study, a cohort of 470 men aged between 47 and 68 years (mean 57.78±4.81) were treated with finasteride (5 mg/day). A second cohort of 230 men aged between 52 and 72 years (mean 62.62±4.65) were treated with tamsulosin (0.4 mg). All men were followed up for 45 months. At intervals of 3 months and at each visit, plasma testosterone (T) levels and the international index of erectile function (IIEF-EF) questionnaire scores were determined.

RESULTS

Long-term treatment with finasteride therapy is associated with worsening of erectile dysfunction (ED) as shown by the significant decrease in the IIEF-EF scores in men treated with finasteride. No worsening of ED was observed in men treated with tamsulosin. The increase in ED due to finasteride did not resolve with continued treatment with finasteride. Most importantly, long-term finasteride therapy resulted in reduction in total T levels, contributing to a state of hypogonadism. On the contrary, no changes in T levels were noted in men treated with tamsolusin.

CONCLUSION

Our findings suggest that in men with BPH, long-term finasteride therapy but not tamsulosin results in worsening of ED and reduces total T concentrations. Clinicians are urged to discuss the impact of 5α-RIs therapy on sexual function with their patients before commencing this therapy.

Biotransformation of finasteride by Ocimum sanctum L., and tyrosinase inhibitory activity of transformed metabolites: experimental and computational insights

Transformation of Finasteride (I) by cell suspension cultures of Ocimum sanctum L. was investigated. Fermentation of compound (I) with O. sanctum afforded three oxidized derivatives, 16β-hydroxyfinasteride (II), 11α-hydroxyfinasteride (III) and 15β-hydroxyfinasteride (IV). Among these metabolites, compound (II) was a new metabolite. Compound (I) and its derivatives were studied for their tyrosinase inhibition assay. All test compounds exhibited significant activity compared to standard drug kojic acid, with compound IV being the most potent member with an IC50 of 1.87μM. Molecular docking revealed significant molecular interactions behind the potent tyrosinase inhibitory activity of the tested compounds.

Molecular interactions of progesterone derivatives with 5 alpha-reductase types 1 and 2 and androgen receptors

The aim of this study was to ascertain the inhibitory effect of several progesterone derivatives for 5 alpha-reductase types 1 and 2 isozymes and to determine the binding to the androgen receptor. The 3,20-dioxopregna-4-ene-17 alpha-yl acetate 4 containing an acetoxy group in C-17 and steroid 17 alpha-hydroxypregn-4-ene-3,20-dione 5 having a hydroxyl group in the same position inhibited both isozymes. On the other hand, 17 alpha-hydroxy-4,5-epoxypregnan-3,20-dione 6 with an epoxy function at C-4, inhibited only the type 1 enzyme. Steroid 4-chloro-17 alpha-hydroxypregn-4-ene-3,20-dione 7a and 4-bromo-17 alpha-hydroxypregn-4-ene-3,20-dione 7b having the C-4 conjugated system and a chlorine or a bromine atom at C-4 respectively, inhibited both types of 5 alpha-reductase. These results indicate that an increase in the electronegativity of ring A produces a major inhibitory activity for 5 alpha-reductase type 1; however this increase was not observed for type 2 enzyme. When the free hydroxyl group of 7a or 7b was esterified, compounds 3,20-dioxo-4-chloropregn-4-ene-17 alpha yl-4-ethylbenzoate 8a and 3,20-dioxo-4-bromopregn-4-ene-17 alpha yl-4-ethylbenzoate 8b were obtained; these steroids inhibited only the 5 alpha-reductase type 2 enzyme. Finasteride and steroids 4, 5, 7b, 8a showed a comparable in vivo pharmacological activity, however the IC(50) values of these compounds were higher as compared to that of finasteride. These results indicated also that steroids 4, 5, 7a, and 7b bind to the androgen receptor whereas compounds 6, 8a and 8b failed to do so. The overall data from this study showed that steroids 5 and 7b bind to the AR and decreased of the growth of prostate and seminal vesicles. Moreover, 4 decreased also the growth of seminal vesicles.

Steroidogenesis inhibitors alter but do not eliminate androgen synthesis mechanisms during progression to castration-resistance in LNCaP prostate xenografts

In castration-resistant prostate cancer (CRPC) many androgen-regulated genes become re-expressed and tissue androgen levels increase despite low serum levels. We and others have recently reported that CRPC tumor cells can de novo synthesize androgens from adrenal steroid precursors or cholesterol and that high levels of progesterone exist in LNCaP tumors after castration serving perhaps as an intermediate in androgen synthesis. Herein, we compare androgen synthesis from [(3)H-progesterone] in the presence of specific steroidogenesis inhibitors and anti-androgens in steroid starved LNCaP cells and CRPC tumors. Similarly, we compare steroid profiles in LNCaP tumors at different stages of CRPC progression. Steroidogenesis inhibitors targeting CYP17A1 and SRD5A2 significantly altered but did not eliminate androgen synthesis from progesterone in steroid starved LNCaP cells and CRPC tumors. Upon exposure to inhibitors of steroidogenesis prostate cancer cells adapt gradually during CRPC progression to synthesize DHT in a compensatory manner through alternative feed-forward mechanisms. Furthermore, tumors obtained immediately after castration are significantly less efficient at metabolizing progesterone ( approximately 36%) and produce a different steroid profile to CRPC tumors. Optimal targeting of the androgen axis may be most effective when tumors are least efficient at synthesizing androgens. Confirmatory studies in humans are required to validate these findings.

In vivo and in vitro effect of novel 4,16-pregnadiene-6,20-dione derivatives, as 5alpha-reductase inhibitors

In this study, we report the synthesis and biological evaluation of several new 3-substituted pregna-4,16-diene-6,20-dione derivatives (11a-11d). These compounds were prepared from the commercially available 16-dehydropregnenolone acetate. The biological effect of these steroids was demonstrated in in vivo and in vitro experiments. In the in vivo experiments, we measured the activity of the 11a-11d on the weight of the prostate gland of gonadectomized hamsters treated with testosterone plus finasteride or with the new steroids. For the studies in vitro, we determined the IC50 values by measuring the steroid concentration that inhibits 50% of the activity of 5alpha-reductase present in human prostate. In order to study the mechanism of action of 11a-11d, we also determined the capacity of these steroids to bind to the androgen receptor (AR) present in the rat prostate cytosol using labeled mibolerone as a tracer. The results from this work indicated that compounds 11a-11d significantly decreased the weight of the prostate as compared to testosterone treated animals and this reduction of the weight of the prostate was comparable to that produced by the finasteride. On the other hand 11a-11d exhibited a high inhibitory activity for the human 5alpha-reductase enzyme with IC50 values of 1.4 x 10(-8), 1.8 x 10(-9), 1.0 x 10(-8) and 4 x 10(-5) respectively. However the IC50 value of 11a (1.8 x 10(-9)) was the only one lower than that of finasteride (8.5 x 10(-9)). Nevertheless this compound did not show a higher potency in vivo as compared to that of compounds 11b-11d. The competition analysis for the androgen receptor indicated that the IC50 value of non-labeled mibolerone used in this experiment was 1nM, whereas steroids 10, 11a-11d did not inhibit the labeled mibolerone binding to the androgen receptor. On the other hand, steroid 10 did not show any activities in vitro or in vivo, and for this reason these steroidal derivatives (11a-11d) cannot be considered as prodrugs of compound 10. In conclusion, the compounds containing chlorine 11a, bromine 11b, iodine 11c atoms, and 11d (without any substituent in the ester moiety) at C-3 produce a significant decrease of the prostate weight in castrated animals treated with T and inhibits the activity of the 5alpha-reductase. Apparently the presence of the halogen atoms in compounds 11a-11c enhances the inhibitory activity for the 5alpha-reductase enzyme.

Evaluation of an eucalyptus oil containing topical drug delivery system for selected steroid hormones

In the present study the permeation and the chemical stability of 17-beta-estradiol, progesterone, cyproterone acetate and finasteride incorporated in an eucalyptus oil containing microemulsion system have been investigated. The formulations contained 1% (w/w) of the steroid hormones. Self diffusion coefficients determined by pulsed-field-gradient spin echo NMR spectroscopy were used to characterise the microemulsion. From these results a bicontinuous structure is proposed for the multicomponent system. However a correlation between the self diffusion of the hormones in the vehicle and the transdermal flux was not indicated. Explanations for this were self assembling, formation of aggregates between the components of the microemulsion and drugs and different effects because of different solubility of the drugs. By addition of certain polymers the skin permeation rates could be improved with exception of cyproterone acetate. Beside standard diffusion experiments, the residual drug content in the skin was investigated. Drug stability was monitored by analysing the steroid hormone content in the different formulations over an observation period of 6 weeks and could be improved by polymers. In addition, viscosity measurements were performed. They indicated an influence of the polymers and drugs on the viscosity in all formulations.

Skin permeation of different steroid hormones from polymeric coated liposomal formulations

In this study, the effect of various polymers (polycarbophil, chitosan-EDTA, polymeric emulsifier and carrageenan) on the permeation, the chemical and microbial stability of 17-beta-estradiol, progesterone, cyproterone acetate (cpa) and finasteride incorporated in DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine) liposomes has been investigated. The liposomes contained 1% (w/w) of the steroid hormones. Standard diffusion experiments were performed. Drug stability was monitored by analysing the steroid hormone content in the different formulations over a time period of 8 weeks and visually inspecting for microbial contamination. In addition, viscosity measurements were performed. The permeation rate could be improved by addition of polymeric agents depending on their type and drug. In all tested formulations, finasteride exhibited the highest diffusion. Both the chemical and the microbial stability of the hormones were significantly improved by the polymers in comparison to the pure liposomes after an observation period of 8 weeks. After that time microbial stability was still evident for all semisolid formulations. In contrast to this in the pure liposomes already after 2 weeks the steroid drugs showed complete insufficient chemical stability and microbial contamination. Additional rheological measurements indicated an influence of the polymers and drugs on the viscosity in all formulations. The elasticity predominated in nearly all polymeric formulations.

Efficacy and tolerability of finasteride 1 mg in men aged 41 to 60 years with male pattern hair loss

A 24-month double-blind, randomized, placebo-controlled, parallel-group, multicenter study of 424 men was conducted to determine the efficacy and tolerability of finasteride 1 mg on hair growth/loss in men aged 41 to 60 years with mild-to-moderate, predominantly vertex male pattern hair loss. Efficacy was evaluated by review of global photographs of the vertex scalp taken at baseline and at Months 6, 12, 18, and 24 and by patient self-assessments and investigator clinical assessments of change from baseline in hair growth/loss collected at Months 6, 12, 18, and 24. Safety analyses included assessment of clinical and laboratory adverse experiences, including sexual adverse experiences. Analysis of global photographic assessment data showed significant improvement in hair growth for men in the finasteride group compared with those taking placebo beginning at Month 6 (p < 0.001) and maintained through Month 24 (p < 0.001). Results of the patient self-assessment and investigator assessments were consistent with those from the global photographic assessment. Finasteride 1 mg improved scalp hair growth in men aged 41 to 60 years with predominantly vertex male pattern hair loss compared with results seen with placebo. Improvement was evident by 6 months of treatment and continued through 24 months. Treatment with finasteride 1 mg was generally well tolerated.

Androgens and alopecia

Androgens have profound effects on scalp and body hair in humans. Scalp hair grows constitutively in the absence of androgens, while body hair growth is dependent on the action of androgens. Androgenetic alopecia, referred to as male pattern hair loss (MPHL) in men and female pattern hair loss (FPHL) in women, is due to the progressive miniaturization of scalp hair. Observations in both eunuchs, who have low levels of testicular androgens, and males with genetic 5alpha-reductase (5alphaR) deficiency, who have low levels of dihydrotestosterone (DHT), implicate DHT as a key androgen in the pathogenesis of MPHL in men. The development of finasteride, a type 2-selective 5alphaR inhibitor, further advanced our understanding of the role of DHT in the pathophysiology of scalp alopecia. Controlled clinical trials with finasteride demonstrated improvements in scalp hair growth in treated men associated with reductions in scalp DHT content, and a trend towards reversal of scalp hair miniaturization was evident by histopathologic evaluation of scalp biopsies. In contrast to its beneficial effects in men, finasteride did not improve hair growth in postmenopausal women with FPHL. Histopathological evaluation of scalp biopsies confirmed that finasteride treatment produced no benefit on scalp hair in these women. These findings suggest that MPHL and FPHL are distinct clinical entities, with disparate pathophysiologies. Studies that elucidate the molecular mechanisms by which androgens regulate hair growth would provide greater understanding of these differences.

Caution on the use of saliva measurements to monitor absorption of progesterone from transdermal creams in postmenopausal women

OBJECTIVES

To determine the levels of progesterone in plasma, red cells and saliva as well as pregnanediol-3-glucuronide excretion in postmenopausal women using transdermal progesterone creams.

METHODS

A double-blind placebo controlled study was carried out using 24 postmenopausal women. Creams (placebo, 20 or 40 mg progesterone/g) were applied twice daily for 3 weeks followed by 1 week without before a further 3-week treatment. Morning samples were collected at 0, 1, 3, 4, 7 and 8 weeks for analysis.

RESULTS

There were small increases in plasma progesterone levels and pregnanediol-3-glucuronide excretion compared to the placebo group and red cell progesterone levels never exceeded plasma levels during progesterone cream use. Saliva progesterone levels were very high and variable in the progesterone cream groups compared to the placebo group and presented a paradox to the usual relationship observed between plasma and saliva progesterone in premenopausal women.

CONCLUSION

The absorption of progesterone from transdermal creams is low and we caution against the use of saliva measurements to monitor progesterone absorption. The low systemic absorption of progesterone may not be due to peripheral conversion by 5 alpha-reductase(s). We also conclude that the low level of progesterone associated with red cells suggests they are not important in the delivery of progesterone to target tissues.

Separation of finasteride and analogues

This review is focused on the different chromatographic strategies for determination of finasteride and its analogues in biological fluids. These compounds are used for the treatment of benign prostatic hyperplasia. Particular attention is paid to high-performance liquid chromatography with spectrophotometric and mass spectrometric detection, the clean-up procedures are also included. The relationships between pharmacokinetics of finasteride, dose administered and required limit of quantitation of the chromatographic assays are discussed. Tandem mass spectrometry is recommended as the detection method for measuring concentrations <1 ng/ml, while cheaper spectrophotometric detection may be selected for determination of higher concentrations.

Disposition and metabolism of finasteride in dogs

Finasteride (FIN) is a potent 5 alpha-reductase inhibitor that has shown clinical success in treating men with benign prostatic hyperplasia. In the study of biological effects and metabolism of FIN in animals, the dog serves as the primary modality. This study was conducted to determine the pharmacokinetics and fate of FIN after oral administration of single doses of [14C]FIN to dogs at 10 and 80 mg/kg (N = 2 and 3, respectively), and also after intravenous infusion at 5 mg/kg (N = 2). Plasma, urine, and feces were analyzed for total 14C content. Parent drug and metabolites in plasma and excreta were measured by HPLC/UV/radioassay and identified by NMR spectroscopy and MS, FIN was subject to extensive biotransformation before excretion. Structures were determined for the major metabolites in plasma, urine, and feces. The primary metabolic events for FIN were hydroxylation of the t-butyl side chain to give hydroxymethyl-FIN (metabolite I), which is oxidized further to form the carboxylic acid derivative (metabolite IV), and hydroxylation at positions B alpha and 15. Terminal half-life of FIN after the intravenous dose was 3.4 hr. Plasma clearance and volume of distribution at steady-state were 4.8 ml/min/kg and 1.1 liter/kg. Dogs showed rapid absorption after oral administration of the low dose, with Cmax reached in the 1-2 hr, bioavailability was estimated to be > 90%. After either dosing route, 45% of the plasma radioactivity (as represented by AUC) was parent drug, 43% was metabolite I, and 1% was metabolite IV. After oral administration, the 80 mg/kg dose was absorbed slowly, with the highest levels of radioactivity in plasma reached in 4-30 hr. Average Cmax value for FIN and metabolite I increased in a dose-related, but nonproportional, manner. Compared with the 10 mg/kg dose, it seems the higher dose was reasonably well-absorbed, as indicated by the nearly proportional increase of AUC values of total radioactivity and FIN. Composition of plasma metabolites observed at the 80 mg/kg dose level was similar to that observed previously for the low dose, suggesting that an increase in plasma exposure was effected in dogs receiving FIN at 80 mg/kg in toxicity studies. Most of the administered radioactivity was recovered in feces after all doses. Little of the intravenous and low oral doses, but > 50% of the 80 mg/kg oral dose, was excreted as intact FIN, suggesting that metabolism might have been saturated at the high dose.

Identification of human cytochrome P450 isozymes responsible for the in vitro oxidative metabolism of finasteride

Finasteride, a prescription drug for the treatment of benign prostatic hypertrophy and alleviation of symptoms associated with benign prostatic hypertrophy and alleviation of symptoms associated with benign prostatic hypertrophy, has been shown to be metabolized in rat hepatic microsomes by hydroxylation at the t-butyl group (omega-OH finasteride), followed by further oxidation to the corresponding acid (omega-oic acid finasteride), with omega-aldehyde finasteride as an intermediate. In this study, we identified specific human cytochrome P450 (CYP) isozyme(s) involved in the in vitro metabolism of [14C]finasteride using CYP isozyme-selective inhibitors and microsomes containing specific recombinant human CYP isozymes (expressed in human AHH-1 TK+/-cells). Each of the three steps of the oxidative pathway was examined separately by using [14C]finasteride and its consecutive metabolites (omega-OH finasteride and omega-aldehyde finasteride) as substrates, and human liver microsomes or expressed recombinant CYP isozymes as the enzyme source. Gestodene, a mechanism-based inhibitor of CYP3A isozymes, showed a concentration-dependent inhibition of the oxidative metabolism of [14C]finasteride. In addition, the respective omega-OH finasteride and omega-oic acid finasteride metabolites were generated only by microsomes containing recombinant CYP3A4, but not the other isozymes (CYP1A1, CYP2B6, CYP2C8, CYP2C9, CYP2D6, and CYP2E1). Similar results were obtained for the oxidation of omega-OH finasteride to omega-aldehyde finasteride, suggesting that human CYP3A isozymes were involved in the oxidation of omega-OH finasteride. When omega-aldehyde finasteride was incubated with human liver microsomes in the presence of an NADPH regenerating system, both the omega-oic acid finasteride and the omega-OH finasteride were detected, suggesting that oxidative and reductive reactions were occurring simultaneously and that they were NADPH- or NADP-dependent. Inhibitors of CYP3A isozymes inhibited the oxidation of omega-aldehyde finasteride in a concentration-dependent manner; an increase in the reduction was also observed, presumably caused by inhibition of the competitive oxidative reaction. Other selective CYP inhibitors for CYP1A1/2 (alpha-naphthoflavone), CYP2C8-10 (sulfaphenazole), CYP2D6 (quinidine), and CYP2E1 (diallylsulfone) showed minor or no effects on both reactions. Consistent with these results, only microsomes containing human recombinant CYP3A4 catalyzed the oxidation of omega-aldehyde finasteride to omega-oic acid finasteride. These results indicate that the oxidation of omega-aldehyde finasteride was NADPH-dependent and was mediated at least in part by CYP3A4. In addition, NAD-dependent enzymes in cytosolic, microsomal, and mitochondrial fractions were capable of oxidizing omega-aldehyde finasteride to omega-oic acid finasteride. Other cellular fractions, particularly mitochondria, were shown to convert finasteride to omega-oic acid finasteride in a similar fashion.

Finasteride: a clinical review

Finasteride is the first of a new class of 5 alpha-reductase inhibitors which allows selective androgen deprivation affecting dihydrotestosterone (DHT) levels in target organs such as the prostate and scalp hair without effecting circulating levels of testosterone thus preserving the desired androgen mediated effects on muscle strength, bone density and sexual function. Finasteride has been demonstrated to produce significant effects in men with an enlarged prostate gland. The long-term data now emerging suggests that progression of benign prostatic hyperplasia (BPH) may be arrested providing additional long term benefits. Experimental uses in prostate cancer prevention and male pattern baldness offer new and exciting possibilities for this class of compounds.

Biotransformation of finasteride (MK-0906) by Selenastrum capricornutum (green algae)

Finasteride (MK-0906), a drug used for the treatment of benign prostatic hyperplasia, is a highly specific inhibitor of steroid 5 alpha-reductase, an enzyme that converts testosterone (T) to dihydrotestosterone (DHT) in animals and humans. In a study to evaluate the effect of finasteride on the growth of green alga, Selenastrum capricornutum, the parent drug was not detected by HPLC in the posttreatment (14 day) samples, suggesting complete biotransformation. Thermospray LC/MS, followed by NMR analysis, indicated that the major algal metabolite was 11 alpha-hydroxy-finasteride. This metabolite has negligible in vitro bioactivity against human prostatic 5 alpha-reductase; its potency is only 2% that of finasteride. The primary metabolite of finasteride produced by the green alga involved a biotransformation not previously observed in mammalian and human studies. The green alga effectively deactivates the drug, thereby mitigating any potential environmental impact.

Metabolism of finasteride in rat hepatic microsomes: age and sex differences and effects of P450 inducers

1. The age- and sex-related metabolism of finasteride and the effects of P450 inducers and inhibitors were investigated using rat hepatic microsomes. 2. No marked age difference (3-13 weeks) in the rates of finasteride disappearance and the formation of 1 (omega-hydroxyfinasteride) and 4 (6 alpha-OH finasteride) was observed in the male rat. Whereas the rate of 1 formation remained about the same in male rat aged 1 year as compared with rat aged 7 weeks, a 21 and 45% decrease in the rate of finasteride disappearance and 4 formation, respectively, were observed. 3. The rates of finasteride disappearance and metabolite formation 1 and 4 in the female rat decreased with an increase in age (3-7 weeks). Metabolite 4 was hardly formed by the hepatic microsomes from the female rat at 7 weeks of age. 4. Hepatic microsomes from the male rat treated with phenobarbital (PB) and dexamethasone (Dex) increased the rate of the finasteride disappearance (PB, 5.5-fold; Dex, 11.6-fold), whereas no increase in this activity was observed after administration of beta-naphthoflavone (BNF). Similarly, pretreatment of the female rat with PB and Dex resulted in increases of 26.6 and 8.4-fold in the rate of finasteride disappearance, respectively, whereas no inductive effect on this activity was observed in the BNF-treated female rat. 5. These observations suggest that finasteride is metabolized by P4502B, P4502C, and P4503A subfamilies in the male rat and by P4502B and P4502C subfamilies in the female rat.

Endocrine properties of the testosterone 5 alpha-reductase inhibitor turosteride (FCE 26073)

Turosteride was tested in a series of studies for its effect on 5 alpha-reductase and for its possible influence on other steroidogenic enzymes and on steroid receptors. The compound was found to inhibit human and rat prostatic 5 alpha-reductases with IC50 values of 55 and 53 nM, respectively, whereas it caused a less marked inhibition of the dog enzyme (IC50 2.2 microM). Turosteride showed no relevant effect on rat adrenal C20,22-desmolase (IC50 254 microM) and human placental aromatase (IC50 > 100 microM), and only at relatively high concentrations it caused inhibition of human placental 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD-I) (IC50 2.5 microM). Turosteride was found to be a selective 5 alpha-reductase inhibitor showing no noteworthy binding to receptors for androgens (relative binding affinity, RBA, 0.004%), estrogens (< or = 0.005%), progesterone (< 0.005%), glucocorticoids (< 0.01%) and mineralocorticoids (< 0.03%). Its biochemical profile was similar to that of finasteride, whereas 4-MA (17 beta-N,N-diethyl-carbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one) was confirmed to be a non-selective 5 alpha-reductase inhibitor, showing a degree of binding affinity to the androgen receptor (RBA 0.1%) and a marked inhibition of 3 beta-HSD-I (IC50 32 nM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, turosteride reduced the ventral prostate and seminal vesicle growth promoting effect of TP, with IC50 values of approximately 5 and 6.7 mg/kg/day, whereas levator ani weight was unchanged. In comparison, 4-MA was approx. 3-fold less potent than turosteride in reducing the prostate and seminal vesicle weights and caused a marked reduction of levator ani weight, thus showing its unselectivity.