Dose Of Flutamide Research Articles

Insulin and glucose responses to hypoxia in male and female neonatal rats: Effects of the androgen receptor antagonist flutamide.

Hypoxia is common with preterm birth and may lead to long‐term effects on adult pancreatic endocrine function and insulin sensitivity. This phenomenon may be sexually dimorphic due to the hypoxia‐induced augmentation of the neonatal androgen surge in male newborns. We evaluated this phenomenon by pretreating neonatal rats on postnatal days (PD) 1, 6, 13, or 20 with flutamide (a nonsteroidal androgen receptor antagonist) at a standard or a high dose (10 or 50 mg/kg) compared to vehicle control. One day later, neonatal rats were exposed to either acute normoxic or hypoxic separation (fasting) for 90 min, and blood was sampled for the measurement of insulin and glucose and the calculation of HOMA‐IR as an index of insulin resistance. During normoxic and hypoxic separation (fasting), flutamide increased insulin secretion in PD2, PD7, and PD14 pups, high dose flutamide attenuated insulin secretion, and high dose flutamide attenuated the increase in HOMA‐IR due to hypoxia. Our studies suggest a unique role of the androgen receptor in the control of neonatal pancreatic function, possibly by blocking a direct effect of neonatal testosterone or in response to indirect regulatory effects of androgens on insulin sensitivity.

Carbendazim-induced androgen receptor expression antagonized by flutamide in male rats

Carbendazim, a widely used fungicide, exhibits reproductive and developmental toxicity. The objective of this study was to investigate the expression of androgen receptor induced by carbendazim and the antagonistic effect of flutamide. Rats were treated with carbendazim, flutamide or a combination of both to measure androgen receptor mRNA, immune activity and protein expression. Carbendazim treatment increased androgen receptor mRNA in a dose-dependent manner, while flutamide, an androgen receptor antagonist, blocked the androgen receptor mRNA. Co-treatment with carbendazim and various flutamide doses decreased the androgen receptor mRNA in a dose-dependent manner. Conversely, co-treatment with flutamide and various carbendazim doses increased the androgen receptor mRNA in a dose-dependent manner. Immunohistochemistry and Western blot analyses showed that carbendazim increased androgen receptor activity (especially in rat testes) in a dose-dependent manner, while flutamide decreased it. Furthermore, carbendazim or flutamide treatment for 7 days increased testosterone and follicular stimulating hormone concentrations in the serum of male rats in a dose-dependent manner, which might involve the disruption of the androgen receptor. Although we need to examine the exact mechanism of androgen receptor involved in the reproductive toxicity and endocrine-disrupting activity induced by carbendazim and its parent, benomyl, we should first discuss how to take advantage of flutamide antagonism on carbendazim-induced reproductive and endocrine-disrupting activity possibly in human. In summary, carbendazim induced androgen receptor expression in mRNA and protein levels, while flutamide antagonized this effect. This is the first report on the antagonistic effect of flutamide on the carbendazim-androgenic effect on mRNA and protein levels. The results would help to clarify the mechanism of carbendazim- and chemical-induced developmental toxicity and endocrine-disrupting activity.

Impact of a health alert and its implementation on flutamide prescriptions for women: an interrupted time series analysis

BackgroundOff-label drug use among ambulatory patients is often based on little or no scientific support. This paper reports the impact of a health warning about the risks of off-label flutamide use by women and the actions subsequently implemented by the public health service targeting such use.MethodThe study was undertaken in a region in north-west Spain. We designed a segmented regression model of an interrupted time series, in which the dependent variable was the monthly value of defined daily doses of flutamide per 1000 inhabitants/day (DDD/TID), both total and stratified by sex. The following two data sources were used: flutamide prescriptions billed to the Spanish National Health Service; and flutamide deliveries made by wholesale drug distributors to pharmacies. The intervention assessed consisted of the issue of an official health warning and the actions subsequently taken to implement it.ResultsThere was an immediate reduction of 49.33% in DDD/TID billed to the Spanish National Health Service in respect of women; the mean value of the population percentage of DDD/TID of flutamide billed in respect of women fell from 34.4% pre-intervention to 23.72% post-intervention. There was an immediate reduction of 19.92% (95%CI: 6.68–33.15%) in total DDD/TID invoiced. There were no significant changes in DDD/TID billed in respect of men or in flutamide use in the private medical sector.ConclusionsOff-label drug misuse is a reality among ambulatory patients, even after actions are implemented following a toxicity warning issued by the competent Health Authority.

Activation of androgen receptors protects intact male mice from memory impairments caused by aromatase inhibition

Although 17β-estradiol (E2) is known to regulate hippocampal function, the specific contributions of hippocampally-synthesized E2 remain unclear. Infusion of the aromatase inhibitor letrozole into the dorsal hippocampus (DH) of ovariectomized mice disrupts object recognition and object placement memory consolidation, suggesting that DH-synthesized E2 is essential for memory. However, the role of DH-synthesized E2 in memory among male rodents is unknown. Here, we examined effects of aromatase inhibition on memory consolidation in male mice. Intact and gonadectomized mice were infused with vehicle or letrozole into the DH immediately post-training in object placement and object recognition tasks. Letrozole blocked memory in both tasks among gonadectomized males only, suggesting that circulating androgens, or a rise in hippocampal androgens due to aromatase inhibition, may support memory consolidation in intact males. To test this hypothesis, intact males were infused with the androgen receptor antagonist flutamide into the DH after object training. A dose-dependent impairment was observed in both tasks, indicating that blocking androgen signaling can impair memory consolidation. To test if hippocampal androgen receptor activation protected intact males from the impairing effects of letrozole, a non-impairing dose of flutamide was co-infused with letrozole. Co-administration of both drugs blocked object placement and object recognition memory consolidation, demonstrating that letrozole impairs memory in intact males only if androgen receptors are blocked. Together, these data suggest that DH-synthesized E2 and androgen receptor activation may work in concert to mediate memory consolidation in intact males, such that androgen receptor activation protects against memory impairments caused by aromatase inhibition.

Very low dose of flutamide in the treatment of hyperandrogenism

Hyperandrogenism is a condition affecting 5–10% of adolescents. The aim of this study was to evaluate the efficacy of very low dose of flutamide in the treatment of hyperandrogenism in adolescence. One hundred and fifty-eight patients, presenting severe acne and/or hirsutism, received 62.5 mg/day of flutamide + ethinylestradiol + gestodene for 18 months. The patients were subjected to assessments of hepatic enzymes levels. Thirty subjects treated with drospirenone + ethinylestradiol represented the control group. After 18 months of treatment, it was obtained a decrease of hirsutism (−39.9%), an almost recovery of acne (98% of patients) with better results of those obtained in control group. Only one case of light hypertransaminasemia was recorded, regressed spontaneously. Very low dose of flutamide was successful and safe and in the treatment of hyperandrogenism in adolescence.

Pharmacokinetics of the anti-androgenic drug flutamide in healthy stallions

Alternatives to surgical castration are necessary for controlling the sexual behaviour of stallions with breeding potential in training and competition. Flutamide is a potent selective non-steroidal androgen receptor competitive antagonist that has been used in human beings as an anti-androgenic drug. In this study, the pharmacokinetics and bioavailability of flutamide and its main active metabolite, 2-hydroflutamide, were determined in seven healthy mature stallions. Single doses of flutamide (1mg/kg intravenously, 1mg/kg orally in fasted horses, 5mg/kg orally in fasted horses and 5mg/kg orally in fed horses) were administered randomly at intervals of 2 weeks. All horses had full physical examinations and blood samples were collected for pharmacokinetics, complete blood counts and biochemistry before and after drug administration. Administration of flutamide did not result in any abnormalities on physical examination or in blood parameters. After intravenous administration of flutamide, the volume of distribution was 0.83L/kg and clearance was 1.20L/h/kg. Flutamide and its metabolite had high protein binding values (93–97%). After oral administration, flutamide was rapidly transformed to 2-hydroxyflutamide, with areas under the concentration–time curve ratios of metabolite:drug ∼7. Oral bioavailability was 6.63% after 1mg/kg flutamide in fasted horses, 6.50% after 5mg/kg flutamide in fasted horses and 6.95% after 5mg/kg in fed horses. Half lives of flutamide were close to 1h after intravenous administration and 2h after oral administration. Half lives of 2-hydroxyflutamide were 4.79–6.84h for all routes and doses. After oral administration, oral flutamide reached plasma concentrations that could be effective as an anti-androgenic agent in horses, but further studies are needed to determine whether flutamide has clinical value as an alternative to castration for controlling sexual behaviour in stallions.

Porcine sertoli cell proliferation after androgen receptor inactivation.

Sertoli cell proliferation in neonatal boars is potentially androgen dependent. Hence, the immediate objective was to evaluate effects of androgen receptor-mediated signaling on the first wave of Sertoli cell proliferation. The experimental design employed littermate pairs of boars with one member assigned to receive a daily oral dose of flutamide, an androgen receptor antagonist, beginning at 1 wk of age and the littermate the canola oil vehicle. Experiment 1 examined the response at 6.5 wk of age after completion of the first wave of Sertoli cell proliferation, and experiment 2 examined the response at 11 wk of age after initiation of the second wave of Sertoli cell proliferation. Experiment 3 was designed to evaluate initial responses at 2, 3, or 4 wk of age. Additional littermates from four of the litters evaluated at 2 wk of age were hemicastrated at 8 days of age. Testis weight increased approximately 50% in the flutamide-treated boars compared with vehicle-treated littermates (P = 0.01) by 6.5 wk of age. Approximately 80% more Sertoli cells/testis were present in flutamide-treated boars at 6.5 wk of age compared with their vehicle-treated littermates (P < 0.01). Animals that were hemicastrated at 8 days of age had more Sertoli cells/testis than their intact littermates at 2 wk of age (P < 0.01), but flutamide inhibited the hemicastration response. Androgen receptor antagonism during postnatal Sertoli cell proliferation increases Sertoli cell numbers, as does hemicastration, but receptor antagonism initially inhibits Sertoli cell proliferation induced by hemicastration.

Clinical Efficacy of Low Dose Flutamide plus Diane-35 in the Treatment of Idiopathic Hirsutism and Polycystic Ovary Syndrome

Idiopathic hirsutism (IH) or polycystic ovary syndrome (PCOS) are the most common causes of hirsutism which affects 5-10% of all women. The aim of this study was to evaluate the efficacy of flutamide plus diane 35 in the treatment of idiopathic hirsutism and polycystic ovary syndrome. 26 polycystic ovary syndrome and 24 idiopathic hirsutism patients were evaluated. Fifty patients were divided into two groups according to their diagnosis: idiopathic hirsutism or polycystic ovary syndrome. All patients received 125 mg Flutamide once a day and Diane 35 tablets for 21 days of each month, for 12 months. We measured hirsutism scores and hormonal levels of all patients. Evaluations were done before treatment, in the 6th and 12th months of therapy. There were no significant differences in Ferriman-Gallwey scores at the beginning and at the end of the therapy between the IH and PCOS groups. The decreases in Ferriman-Gallwey scores were significant in both groups in the 6th and 12th month of therapy. Combined treatment significantly decreased total and free testosterone, DHEAS and significantly increased SHBG levels in both groups and additionally decreased levels of LH, androstenodione and LH/FSH ratio in the polycystic ovary syndrome group. Combined treatment was effective and safe in the treatment of hirsutism. Combined regimens have additional effects on the treatment of hirsutism.

Hepatotoxicity with low- and ultralow-dose flutamide: a surveillance study on 203 hyperandrogenic young females

To investigate the impact of low- and ultralow-dose regimens of flutamide on liver function of young hyperandrogenic females. A 10-year surveillance study. University teaching hospital. Two hundred three hyperandrogenic young females (mean age: 20.9 ± 4.9 years). Inclusion criterion was receiving low- or ultralow-dose of flutamide as antiandrogenic treatment. Patients were categorized into Groups A and B, according to the administered dose (Group A = 62.5 mg/daily, Group B = 125 mg/daily). The two groups were further subdivided into subgroups (A1, A2, B1, B2) depending on the coadministration of estroprogestagen oral contraceptives (OCs) (A2, B2). Serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were periodically evaluated and used as markers of hepatotoxicity. Mild-to-severe increase of circulating AST/ALT was detected in 19 (9.4%; 95% CI = 5.9%-14.4%) patients during the first year of treatment (mild = 16 [7.9%, 95% CI = 4.7%-12.7%], moderate = 2 [0.9%, 95% CI = 0.1%-3.9%], severe = 1 [0.5%, 95% CI = 0.0%-3.1%]). No statistical differences were observed in relation to flutamide dose regimens and coadministration of OC. The median time to hypertransaminasemia was 12 weeks (range: 2-48) with no difference between Group A and Group B. A significant correlation was observed between hepatotoxicity and pretreatment BMI, ALT basal level, and AST basal level. Hepatotoxicity is a rare but possible event using low- and ultralow-dose regimens of flutamide. We need larger study populations in order to identify risk patterns for hepatotoxicity development.

Optimization and Evaluation of Micromeritic and Release Properties of High Dose Flutamide Liquisolid Systems

Flutamide (FLT) is the only presently recommended drug for monotherapy of benign prostatic hypertrophy. It is known for its poor solubility and slow dissolution. In this study nine different formulae of liquisolid systems (LS) were prepared using Polyethyleneglycol 400 as a liquid vehicle, Avicel® PH 102 and Aerosil 200 as the carrier and the coating material, respectively. Hydrophilic polymers (PVP, HPMC and PEG 2000) were added at a 10% w/w concentration to improve LS properties. Thermal analysis showed complete absence of drug crystallinity in the prepared LS that indicates successful FLT solubilization. The prepared systems were tested for their micromeritic properties (angle of repose, Carrs index and Hausners ratio). The results showed that all the formulae had acceptable values of the angle of repose except formulae F2 (42.0) and F3 (43.50) indicating reasonable flow properties of the LS systems. Compressed into tablets, formula F8 showed the fastest drug release with about 69% of the drug released after the first 5 minutes and almost all the drug released after one hour. Directly compressed FLT tablets showed very slow release with only 5% and 30% of the drug released after 5 and 120 minutes, respectively. Keywords: Flutamide, Liquisolid systems, PEG 400, PVP, HPMC, PEG 2000, Dissolution rate, FLT, Microsystems, “powdered solution technology”, dry-looking, polyvinyl pyrrolidone (PVP), liquid load factor (Lf), sodium starch glycolate (Explotab), Precompression Studies, Differential Scanning Calorimetry (DSC)

Prostatic stromal cells of old gerbils respond to steroidal blockades creating a microenvironment similar to reactive stroma

The present study examined the changes in prostatic stroma of old gerbils (18 months) submitted to orchiectomy associated or not with steroidal blockades. Animals were divided into six groups, all surgically castrated except the control group composed of intact animals. The other two controls were formed by castrated animals, one that received and one that did not receive the drug vehicle. In the experimental groups, doses of flutamide (10 mg/kg/day) and/or tamoxifen (1 mg/kg/48 h) were applied for 1, 3, 7 and 30 days post-castration. The methodologies involved were: morphological (HE, Gömöri reticulin, Picrosirius-hematoxylin), immunohistochemical (tenascin, type IV collagen) and ultrastructural analyses. Gradually, the epithelial compartment was significantly exceeded in volume by the stromal compartment, characterizing regression but not atrophy of the gland. The smooth muscle cell frequency increased significantly after 30 days and participated effectively in the stromal increase. Large collagen I and tenascin deposits in the subepithelial region were a hallmark of prostatic acini in the experimental groups up to 7 days, while in the 30-day group these elements practically disappear. Fibroblasts with reactive aspect, changes in basement membrane structure and maintenance and/or increase of blood vessels were also associated with treatments. These results showed, in part, the sensitivity of stromal components to suppressed hormones and favored the creation of a differentiated glandular microenvironment. Therefore, the data suggest the importance of considering aging when analyzing aspects of prostatic regression between rodents and humans after hormonal ablation.

Tissue changes in senescent gerbil prostate after hormone deprivation leads to acquisition of androgen insensitivity

The present study examined the response of the prostate epithelium of senescent gerbils submitted to orchiectomy and with or without steroidal blockade. Animals were divided into five groups, all surgically castrated except the control group composed of intact animals. In the experimental groups, doses of flutamide and/or tamoxifen were applied for 1, 3, 7 and 30 days postcastration. The structural methods applied reveal that castration, whether associated or not with anti-steroidal drugs, promoted short- and long-term decrease in wet and relative weights of the prostate. The quantitative decline of epithelial compartment proportion observed at the end of treatment was due to the sum of slight changes in the epithelium and lumen. The apoptotic index had risen significantly at 1 day and declined at 7 days postcastration. Androgen receptor (AR) expression decreased after 3 days of hormonal ablation, coinciding with the highest levels of apoptosis and cell proliferation observed in all treated groups. The majority of cells remained differentiated in all groups due to CK 8/18 expression. Some animals remained with injuries such as carcinomas and adenocarcinomas after hormonal ablation. In the latter a mixture of AR-positive and AR-negative cells was identified. Microinvasive carcinomas found in the group treated for 30 days consisted of PCNA-positive, inflammatory and non-proliferating cells. Low apoptosis incidence and bcl-2 positive cells were observed in these lesions. The treatments promoted a reduction of lesions in older gerbils, but treatment-resistant tumours will improve understanding of the events that lead to hormone resistance.

OECD validation of phase‐3 Hershberger assay using the stimulated weanling male rat in Korea

The OECD has proposed a new, validated test guideline with the stimulated weanling male Hershberger assay to avoid the surgical castration step. In the present study, we assessed the relevance and reliability of the stimulated weanling Hershberger assay in four stages. All chemicals except for testosterone propionate (TP) were orally administered to sexually immature male rats of 22 days old for 10 days. The weights of four mandatory accessory sex organs, two additional reproductive tissues and optional systemic organs were evaluated. At the first two stages, TP, as reference androgen, significantly increased the weights of epididymides and accessory sex organs (ASO) at 1.0 mg kg(-1) and flutamide (FLU), as a positive anti-androgen control, decreased the TP-stimulated organ weights at 3.0 mg kg(-1). At stage 3, trenbolone (40 mg kg(-1)), an anabolic steroid, significantly increased ASO weights, and weak anti-androgens (DDE and linuron) decreased the TP-stimulated ASO weights at each high dose. The above results were confirmed in a blind test with coded substances provided by OECD. Compared with results from our previous castrated male assay, the intact weanling version is less sensitive than the castrated male version, in terms of a smaller response at the reference dose of TP or FLU. However, this study suggests that the stimulated weanling Hershberger assay can detect the effects of both potent and weak anti-androgens on androgen-producing and androgen-dependent tissues.

Flutamide as a tool to study the hormonal regulation of the reproductive tract in the golden hamster.

The effect of flutamide (FLU) administered during 6 weeks at doses of 50 or 100 mg kg-1 body weight, on various reproductive characteristics of sexually active male golden hamsters was studied. The weight of seminal vesicles and epididymides showed a dose dependent inhibition with FLU, while testicular weight exhibited a biphasic response, its value being increased by 20% at lower FLU doses and reduced by 15% at higher FLU doses. An elevation of testicular and epididymal androgen-binding protein (ABP) content and also of testicular testosterone content was observed with both doses of FLU. Serum levels of LH and testosterone exhibited a four-fold increase, at both doses of FLU, while FSH serum level was elevated depending on the dose of FLU used. Results suggest that in the golden hamster the maintenance of the weight of testes and accessory organs depends mainly on androgenic stimulation, while production and transport of ABP is probably regulated by gonadotropins.

Long-Term Efficacy and Tolerability of Flutamide Combined with Oral Contraception in Moderate to Severe Hirsutism: A 12-Month, Double-Blind, Parallel Clinical Trial

Our objective was to test the efficacy and tolerability of three doses of flutamide (125, 250, and 375 mg) combined with a triphasic oral contraceptive (ethynylestradiol/levonorgestrel) during 12 months to treat moderate to severe hirsutism in patients with polycystic ovary syndrome or idiopathic hirsutism. We conducted a randomized, double-blind, placebo-controlled, parallel clinical trial. A total of 131 premenopausal women, suffering from moderate to severe hirsutism, were randomized to placebo or 125, 250, or 375 mg flutamide daily associated with a triphasic oral contraceptive pill. Hirsutism (Ferriman-Gallwey), acne and seborrhea (Cremoncini), and hormone serum levels were monitored at baseline and at 3 (except hormone serum levels), 6, and 12 months. Side effects and biochemical, hematological, and hepatic parameters were assessed. We used three-way ANOVA (subject, dose, and visit) with Scheffé adjustment for multiple comparisons or nonparametrical Friedman test and least-squares mean (paired data) and Kruskall-Wallis test for unpaired data analyses. We used chi(2) or Fisher's test for categorical data. A total of 119 patients were included in the intention-to-treat analysis. All flutamide doses induced a significant decrease in hirsutism, acne, and seborrhea scores after 12 months compared with placebo without differences among dose levels. Similar related side effects were observed with placebo and 125 mg flutamide (12.5%), and slightly higher with 250 mg (17.3%) and 375 mg (21.2%). No statistically significant differences were observed either among doses or compared with placebo. Flutamide at 125 mg daily during 12 months was the minimum effective dose to diminish hirsutism in patients with polycystic ovary syndrome or with idiopathic hirsutism.

Effects of long-term flutamide treatment during development in zebra finches

The molecular mechanisms responsible for the sexual differentiation of the zebra finch song system remain mysterious. Androgen receptors are expressed in a sexually dimorphic fashion in the zebra finch song system: males have more cells expressing androgen receptors, and this sex difference appears very early in development (day 9 posthatch). Estrogen administration to hatchling females up-regulates androgen receptor expression in their song system and profoundly masculinizes their song system's morphology. Co-administering flutamide, an androgen receptor blocker, with estrogen impedes estrogen's masculinizing effects on the song system, suggesting that androgens are required for masculine development. Accordingly, to investigate further the role of androgens in the sexual differentiation of the zebra finch song system, we sought to block androgen activity in males by administering large, sustained doses of flutamide from just before androgen receptors are expressed in the song system (day 7) through to the day of sacrifice (days 61–63). Flutamide profoundly reduced the size of the testes, demonstrating that this drug and mode of administration could have a large impact on tissues. In contrast, flutamide had only a minor impact on the song system: the number of RA neurons was slightly reduced, and the corrected HVC volume showed a trend toward demasculinization. Other brain measures (uncorrected HVC, and corrected and uncorrected volumes of Area X, lMAN, RA, and Rotundus; neuron size in lMAN, HVC, and RA; and number of HVC and LMAN neurons) were not significantly affected. The present results do not support an important role for androgen in masculinizing the song circuit after posthatch day 7.

Involvement of Bile Salt Export Pump in Flutamide-Induced Cholestatic Hepatitis

The non-steroidal antiandrogen flutamide is widely used for treatment of prostatic cancer, but causes side effects, including cholestatic hepatitis and fulminant hepatitis. We investigated the pathogenesis of flutamide-induced cholestatic hepatitis, focusing on the bile salt export pump (BSEP; ABCB11), which exports bile salts to the bile. We examined the inhibitory effects of flutamide and its active metabolite, hydroxyflutamide, on the transport of taurocholic acid (TCA) by membrane vesicles derived from hBSEP-expressing Sf9 cells. Flutamide inhibited the transport of TCA by hBSEP (IC50 value, about 50 microM), while hydroxyflutamide had no effect at up to 100 microM. When flutamide was administered to rats as a single oral dose of 100 mg/kg, the biliary excretion rate of bolus-injected [3H]TCA was decreased and the liver tissue concentration of flutamide exceeded 50 microM. Repeated doses of flutamide for 5 d (10 mg/kg/d) also decreased the biliary excretion rate of bolus-injected [3H]TCA. In this case, the liver tissue concentration of flutamide was below 0.1 microM. In both cases, no change in the mRNA level of rat Bsep was detected by RT-PCR. These results suggest that flutamide itself, but not its major metabolite, may cause cholestasis by inhibiting BSEP-mediated bile salt excretion.

Influence for testicular development and histological peculiarity in the testes of flutamide‐induced cryptorchid rat model

To investigate influence for the testicular development and to assess the usefulness as an animal model, cryptorchid rats were induced by exposure to flutamide during the fetal period and their testes examined histologically. Flutamide was injected into the abdomen of pregnant rats for 7 days from the 14th to 20th day of gestation. The male offspring in which cryptorchidism was observed at 28 days after birth were defined as the model rats. They were divided into four groups by dosage of flutamide (2.5 mg, 5 mg, 7.5 mg, 15 mg per day), and their testicular weight, spermatogenesis (modified Johnsen score), and germ cell apoptosis were examined histochemically at 10 weeks after birth. The incidence of cryptorchidism including both unilateral and bilateral in the 2.5, 5, 7.5 and 15-mg flutamide groups was 58.3%, 81.9%, 93.6% and 91.0%, respectively. In the model rats, the undescended testes were located at the caudal end of the abdominal cavity, and these testes weighed less than the contra-descended testes in each group. Histologically, apoptotic cells were markedly increased, the seminiferous tubules were degenerated and disturbance of spermatid differentiation was observed in the undescended testes compared with the normal or contra-lateral descended testes. We found out that the incidence of undescended testes increased in a flutamide dose-dependent manner. The findings of histological examination were independent of the administrated dose of flutamide and it is suggested that exposure of the testes to abdominal temperature causes spermatogenic arrest with germ cell apoptosis. The present animal model indicates high incidence of above 90%, has no surgical stress and dose not require special techniques. We believe that the present model is a useful tool for the understanding of pathogenesis and treatment of cryptorchidism and further biological research into spermatogenesis.

The OECD Program to Validate the Rat Hershberger Bioassay to Screen Compoundsfor in Vivo Androgen and Antiandrogen Responses. Phase 1: Use of a Potent Agonistand a Potent Antagonist to Test the Standardized Protocol

The Organisation for Economic Cooperation and Development (OECD) has completed phase 1 of the Hershberger validation intended to identify in vivo activity of suspected androgens and anti-androgens. Seventeen laboratories from 7 countries participated in phase 1, and results were collated and evaluated by the OECD with the support of an international committee of experts. Five androgen-responsive tissues (ventral prostate, paired seminal vesicles and coagulating glands, levator ani and bulbocavernosus muscles, glans penis, and paired Cowper’s or bulbourethral glands) were evaluated. The standardized protocols used selected doses of a reference androgen, testosterone propionate (TP), and an antiandrogen, flutamide (FLU). All laboratories successfully detected TP-stimulated increases in androgen-responsive tissue weight and decreases in TP-stimulated tissue weights when FLU was co-administered. The standardized protocols performed well under a variety of conditions (e.g., strain, diet, housing protocol, bedding). There was good agreement among laboratories with regard to the TP doses inducing significant increases in tissue weights and the FLU doses decreasing TP-stimulated tissue weights. Several additional procedures (e.g., weighing of the dorsolateral prostate and fixation of tissues before weighing) and serum component measurements (e.g., luteinizing hormone) were also included by some laboratories to assess their potential utility. The results indicated that the OECD Hershberger protocol was robust, reproducible, and transferable across laboratories. Based on this phase 1 validation study, the protocols have been refined, and the next phase of the OECD validation program will test the protocol with selected doses of weak androgen agonists, androgen antagonists, a 5α-reductase inhibitor, and chemicals having no androgenic activity.

Absence of Hepatotoxicity After Long-Term, Low-Dose Flutamide in Hyperandrogenic Girls and Young Women

Flutamide is a nonsteroidal antiandrogenic agent that to date has been used chiefly in treating prostate cancer. Hepatotoxicity, although rare, is a potentially fatal side effect that has been documented with doses of 750 to 1500 mg daily. Minor hepatotoxicity has been associated with doses as low as 250 mg daily. This study examined the risk of hepatotoxicity when flutamide was given in ultralow doses for up to 3 years and for periods as long as 54 months. Participants were 190 hyperandrogenic girls and young women, 150 of whom had established and 40 incipient polycystic ovary syndrome (PCOS); none were obese. Flutamide was given alone or in combination with metformin, an insulin sensitizer, and/or an estro-progestagen oral contraceptive containing gestodene or drospirenone. Doses of flutamide ranged from 62.5 to 250 mg daily. Circulating levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) served as markers of hepatic toxicity. All participants had normal levels of ALT and AST at baseline, and concentrations were unchanged during flutamide treatment-both 3 months after the start of treatment and at the last assessment, which took place after a mean of 19 months on treatment. Treatment times ranged up to 54 months. No subject had an AST or ALT level of 45 U/L or higher at any time. These findings suggest that flutamide is a safe treatment when used in low dosage to treat hyperandrogenic, nonobese girls and young women having actual or impending PCOS. It remains possible that hepatic toxicity may, in rare instances, develop in patients taking ultralow doses of flutamide. Nevertheless, the investigators anticipate that such doses may become a part of treating hyperandrogenic girls and young women with PCOS. They do recommend that transaminase levels be monitored during flutamide treatment.