Sonochemical synthesis and fabrication of perovskite type calcium titanate interfacial nanostructure supported on graphene oxide sheets as a highly efficient electrocatalyst for electrochemical detection of chemotherapeutic drug.

In green approaches for electrocatalyst synthesis, sonochemical methods play a powerful role in delivering the abundant surface areas and nano-crystalline properties that are advantageous to electrocatalytic detection. In this article, we proposed the sphere-like and perovskite type of bimetal oxides which are synthesized through an uncomplicated sonochemical procedure. As a yield, the novel calcium titanate (orthorhombic nature) nanoparticles (CaTiO3 NPs) decorated graphene oxide sheets (GOS) were obtained through simple ultrasonic irradiation by a high-intensity ultrasonic probe (Titanium horn; 50 kHz and 60 W). The GOS/CaTiO3 NC were characterized morphologically and chemically through the analytical methods (SEM, XRD, and EDS). Besides, as-prepared nanocomposites were modified on a GCE (glassy carbon electrode) and applied towards electrocatalytic and electrochemical sensing of chemotherapeutic drug flutamide (FD). Notably, FD is a crucial anticancer drug and also a non-steroidal anti-androgen chemical. Mainly, the designed and modified sensor has shown a wide linear range (0.015-1184 µM). A limit of detection was calculated as nanomolar level (5.7 nM) and sensitivity of the electrode is 1.073 µA µM-1 cm-2. The GOS/CaTiO3 modified electrodes have been tested in human blood and urine samples towards anticancer drug detection.

Electrochemical determination of anticancer drug, flutamide in human plasma sample using a microfabricated sensor based on hyperbranchedpolyglycerol modified graphene oxide reinforced hollow fiber-pencil graphite electrode.

Flutamide (FLT) is a non-steroidal anti-androgen drug that has a specific anti-androgenic activity so that it is used in the treatment of prostate cancer. FLT may also be used to treat excess androgen levels in women. A sensitive electrochemical sensor based on hyperbranchedpolyglycerol functionalized- graphene oxide developed, using ionic liquid mediated hollow fiber-pencil graphite electrode (HF/HBP-GO/PGE) as a working electrode for determination of an anticancer drug, flutamide (FLT. In this design, a two centimeter piece of porous polypropylene hollow fiber membrane was impregnated with ionic liquid (1-Pentyl-3-methylimidazoliumbromide), and a graphite rod modified with hyperbranchedpolyglycerol/graphene oxide (HBP-GO), was located inside the fiber lumen. The modified electrode exhibits sorption activity, high sensitivity, stability and applicability over a wide range of concentration of FLT. The morphology and the electrochemical properties of the modified electrode were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The effect of the amount of graphene oxide (GO), scan rate, pH, concentration of ionic liquid, extraction time and agitation rate on electrochemical behavior of flutamide molecules was investigated. The square wave voltammetric method showed a linear behavior over the drug concentration range 0.1-110 µM. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be 0.029 µM and 0.099 µM, respectively. The proposed sensor was applied for determination of FLT in human plasma sample with satisfactory results.

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.

Preparation and in vitro-in vivo evaluation of surface-modified poly(lactide-co-glycolide) nanoparticles as controlled release carriers for flutamide delivery.

This investigation explores the use of methoxy polyethylene glycol (mPEG) functionalised poly(D,L-lactide-co-glycolide) (PLGA) nanocrystals of flutamide (FLT) with enhanced solubility, bioavailability and blood circulation time for targeting prostate cancer. FLT had Log P 3.27, short half life 5-6 h, low water solubility, permeability and bioavailability with extensive first-pass metabolism. FLT-loaded nanocrystals were prepared using nanoprecipitation method with surface coating by mPEG and characterised through differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electronic microscopy, particle size, zeta potential, percent entrapment efficiency (% EE), in vitro dissolution, haemolysis, sterility, bioavailability and stability studies. The percent cumulative drug release and % EE of optimised formulation was found to be 95.21 ± 1.18 and 88.36 ± 1.20, respectively, for 48 h. In addition, FLT-loaded PEGylated PLGA nanocrystals exhibited significantly delayed blood clearance with drug level of about 766.71 ng/mL at 48 h. In conclusion, PEGylated PLGA FLT nanocrystals could be demonstrated as a novel approach to enhance solubility, bioavailability and blood circulation time.

Pharmacokinetics of an injectable modified-release 2-hydroxyflutamide formulation in the human prostate gland using a semiphysiologically based biopharmaceutical model.

The local distribution of 2-hydroxyflutamide (2-HOF) in prostate tissue after a single intraprostatic injection of a novel parenteral modified-release (MR) formulation in patients with localized prostate cancer was estimated using a semiphysiologically based biopharmaceutical model. Plasma concentration-time profiles for 2-HOF were acquired from a phase II study in 24 patients and the dissolution of the MR formulation was investigated in vitro. Human physiological values and the specific physicochemical properties of 2-HOF were obtained from the literature or calculated via established algorithms. A compartmental modeling approach was adopted for tissue and blood in the prostate gland, where the compartments were modeled as a series of concentric spherical shells contouring the centrally positioned depot formulation. Discrete fluid connections between the blood compartments were described by the representative flow of blood, whereas the mass transport of drug from tissue to tissue and tissue to blood was described by a one-dimensional diffusion approximation. An empirical dissolution approach was adopted for the release of 2-HOF from the formulation. The model adequately described the plasma concentration-time profiles of 2-HOF. Predictive simulations indicated that the local tissue concentration of 2-HOF within a distance of 5 mm from the depot formulation was approximately 40 times higher than that of unbound 2-HOF in plasma. The simulations also indicated that spreading the formulation throughout the prostate gland would expose more of the gland and increase the overall release rate of 2-HOF from the given dose. The increased release rate would initially increase the tissue and plasma concentrations but would also reduce the terminal half-life of 2-HOF in plasma. Finally, an in vitro-in vivo correlation of the release of 2-HOF from the parenteral MR formulation was established. This study shows that intraprostatic 2-HOF concentrations are significantly higher than systemic plasma concentrations and that increased distribution of 2-HOF throughout the gland, using strategic imaging-guided administration, is possible. This novel parenteral MR formulation, thus, facilitates good pharmacological effect while minimizing the risk of side effects.

Age disrupts androgen receptor-modulated negative feedback in the gonadal axis in healthy men.

Testosterone (T) exerts negative feedback on the hypothalamo-pituitary (GnRH-LH) unit, but the relative roles of the CNS and pituitary are not established. We postulated that relatively greater LH responses to flutamide (brain-permeant antiandrogen) than bicalutamide (brain-impermeant antiandrogen) should reflect greater feedback via CNS than pituitary/peripheral androgen receptor-dependent pathways. To this end, 24 healthy men ages 20-73 yr, BMI 21-32 kg/m2, participated in a prospective, placebo-controlled, randomized, double-blind crossover study of the effects of antiandrogen control of pulsatile, basal, and entropic (pattern regularity) measurements of LH secretion. Analysis of covariance revealed that flutamide but not bicalutamide 1) increased pulsatile LH secretion (P = 0.003), 2) potentiated the age-related abbreviation of LH secretory bursts (P = 0.025), 3) suppressed incremental GnRH-induced LH release (P = 0.015), and 4) decreased the regularity of GnRH-stimulated LH release (P = 0.012). Furthermore, the effect of flutamide exceeded that of bicalutamide in 1) raising mean LH (P = 0.002) and T (P = 0.017) concentrations, 2) accelerating LH pulse frequency (P = 0.013), 3) amplifying total (basal plus pulsatile) LH (P = 0.002) and T (P < 0.001) secretion, 4) shortening LH secretory bursts (P = 0.032), and 5) reducing LH secretory regularity (P < 0.001). Both flutamide and bicalutamide elevated basal (nonpulsatile) LH secretion (P < 0.001). These data suggest the hypothesis that topographically selective androgen receptor pathways mediate brain-predominant and pituitary-dependent feedback mechanisms in healthy men.

Determination of 2-hydroxyflutamide in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS): application to a bioequivalence study on Chinese volunteers.

A sensitive, simple and rapid ultra fast liquid chromatography (UFLC)-ESI-MS/MS method was developed for the determination of 2-hydroxyflutamide in human plasma using tegafur as the internal standard. The plasma sample was pretreated with methanol for protein precipitation and the analytes were separated on an Ultimate C18 column (5 microm, 2.1 mm x 50 mm, MD, USA) with the mobile phase consisted of acetonitrile and water (2:1, v/v). Detection was performed on a triple-quadrupole tandem mass spectrometer under a negative multiple reaction-monitoring mode (MRM). The mass transition ion-pair was followed as m/z 290.90-204.8 for 2-hydroxyflutamide and 198.9-128.8 for tegafur. Linear calibration curves were obtained in the concentration range of 1.742-1452 ng/ml with a lower limit of quantification of 1.742 ng/ml. The intra- and inter-batch precision values were less than 8.1% and 5.6%, respectively. The established method was successfully applied to a bioequivalence study of two flutamide preparations (250 mg) in 20 healthy male volunteers.

Circulating antiandrogenic activity in children with congenital adrenal hyperplasia during peroral flutamide treatment.

CONTEXT: The degree of androgen receptor blockade achieved with peroral flutamide is unknown. OBJECTIVE: The aim of this study was to examine the contribution of flutamide to circulating antiandrogenic activity in children with congenital adrenal hyperplasia using a recombinant cell bioassay. DESIGN: We describe an open-label, prospective clinical study. SETTING: The study was conducted at the Hospital for Children and Adolescents, University of Helsinki, or the Turku University Hospital, Finland. PARTICIPANTS: Seven children, age 7.2-10.5 yr, were included. INTERVENTION: As an experimental approach to improve control of height velocity and the rate of bone maturation, the patients received letrozole (2.5 mg/d) and flutamide (10 mg/kg.d) and were followed up at 3-month intervals for 3-12 months. Before employing the bioassay, two pools of sera (obtained before and during flutamide treatment) were supplemented with increasing amounts of testosterone, and all sera (n = 27) of individual patients were supplemented with a constant amount of exogenous testosterone. MAIN OUTCOME MEASURE: The main outcome measure was circulating antiandrogenic activity. RESULTS: Flutamide and/or its metabolites shifted the dose-response curve of testosterone, in that only the highest testosterone concentration, corresponding to 1803 ng/dl (62.5 nm) in human serum, was measurable by the bioassay. In individual sera supplemented with testosterone, flutamide treatment suppressed androgen bioactivity from 378 +/- 20 ng/dl (13.1 +/- 0.7 nm) (mean +/- sem) (pretreatment) to 110 +/- 20 ng/dl (3.8 +/- 0.7 nm) (3 months), 83.7 +/- 12 ng/dl (2.9 +/- 0.4 nm) (6 months), 46.2 +/- 6 ng/dl (1.6 +/- 0.2 nm) (9 months), and 57.7 +/- 9 ng/dl (2.0 +/- 0.3 nm) (12 months) testosterone equivalents (P < 0.01). CONCLUSIONS: A dose of flutamide less than 10 mg/kg.d appears sufficient to inhibit AR in children. The recombinant cell bioassay employed herein offers a novel means to monitor the treatment of patients receiving antiandrogens.

Application of an antiandrogen during pregnancy infantilizes the male offsprings' behaviour.

The present study was conducted to test the hypothesis that an application of an antiandrogen during pregnancy causes an infantilization of the male offsprings' behaviour later in life. The subjects studied were male guinea pigs whose mothers were either treated with an antiandrogen (flutamide and carrier) or a placebo (carrier only) during pregnancy. The mothers lived in groups of five females and one male. Application of the antiandrogen or the placebo took place on days 30, 32, 34, and 36 of pregnancy, the sensitive phase of foetal CNS sexual differentiation in guinea pigs. After weaning three groups of sons, whose mothers had received the antiandrogen (FT-sons) and five groups of sons, whose mothers had received the placebo (PT-sons) were established. Each group consisted of two males. From their 20th through their 100th day of age, the spontaneous behaviour of the males was recorded in their home cages in 5-day intervals. Additionally, blood samples were collected to determine serum cortisol concentrations. FT-sons and PT-sons did not differ in serum cortisol concentrations. However, distinct differences in behaviour occurred: FT-sons rested significantly longer with bodily contact than PT-sons. Additionally, FT-sons displayed more play-behaviour than PT-sons. These results point to a behavioural infantilization in males prenatally treated with antiandrogen. The behavioural differences between FT- and PT-sons are in accordance with previous studies in which a decrease of serum androgen concentrations in pregnant females living in an unstable social environment [Psychoneuroendocrinology 2001;26:503] and an infantilization of their sons' behaviour was described [Psychoneuroendocrinology 2003;28:67]. Thus, our study supports the hypothesis, that the decrease of androgen concentrations during pregnancy, caused by an unstable social environment, is responsible for the infantilization of the male offsprings' behaviour.

Un nuevo método de cromatografía de líquidos de alto rendimiento y de fase inversa para la determinación de flutamida en liposomas, plasma de sangre de rata y formas de dosificación en comprimidos / A new reverse-phase high performance liquid chromatographic method for determination of flutamide in liposomes, rat blood plasma and tablet dosage forms

La flutamida es un antiandrógeno ampliamente utilizado en el tratamiento del cáncer de próstata que afecta al nivel de antígeno específico de la próstata (PSA) en sangre, lo que requiere que sea estable en la sangre durante el suficiente tiempo. Se ha desarrollado una nueva forma de dosificación farmacéutica, los liposomas, para mejorar la eficacia de este fármaco. El objeto de este estudio es desarrollar un método HPLC UV para la determinación de la FLT en los liposomas, en el plasma de sangre de rata y en distintas formas de dosificación en comprimidos comercializadas. Los pasos de preparación de muestras requieren menos tiempo. El estándar interno (IS) para el procedimiento de ensayo fue la 6-mercaptopurina. Las muestras se inyectaron en la columna de la fase inversa (Thermosil ® C18 ). La fase móvil, metanol: agua (80:20, v/v), se llevo a cabo con una velocidad de flujo de 1 ml/min. durante 8 min. La FLT se detectó mediante un detector de UV con una longitud de onda de 295 nm. Los tiempos de retención del IS y la FLT fueron de 3,03 y 4,02 min. respectivamente. El método fue lineal en el rango de concentración de 20-1000 ng/ml y 50-1000 µg/ml en la fase móvil y en el plasma de sangre de rata respectivamente. Se validó la exactitud, precisión, robustez y recuperación del método. El límite de detección fue de 0,099 µg/ml y de 0,106 µg/ml en la fase móvil y en el plasma de sangre de rata respectivamente. El método demostró ser muy reproducible y parece ser adecuado para el control rutinario de fármaco terapéutico. Se podría utilizar sin ninguna interferencia por parte de lípidos, excipientes de comprimidos y sustancias endógenas de las muestras de plasma

Flutamide is an anti-androgen widely used in treatment of prostate cancer by affecting Prostate Specific Antigen (PSA) level in blood, which requires its stability in blood for enough time. A new pharmaceutical dosage form, liposomes, has been developed for improving efficacy of this drug. The aim of this study is to develop HPLC UV method for the determination of FLT in liposomes, rat blood plasma and different marketed tablet dosage forms. The method involved less time-consuming sample preparation steps. The internal standard (IS) for the assay procedure was 6-Mercaptopurine. The samples were injected on to reverse-phase (Thermosil ® C18 ) column. The mobile phase, Methanol: Water (80:20, v/v)was run at a flow rate of 1 ml/min for 8 min. The FLT was detected by UV detector at 295 nmwavelength. The retention times for IS and FLT were 3.03 and 4.02 min, respectively. The method was linear over the concentration range 20-1000 ng/ml and 50-1000 µg/ml in mobile phase and rat blood plasma, respectively. The method was validated for accuracy, precision, robustness and recovery. The limit of detection was 0.099µg/ml and 0.106µg/ml in mobile phase and rat blood plasma, respectively. The method was shown to be highly reproducible and it seems to be adequate for routine therapeutic drug monitoring. It could be used without any interference from lipids, tablet excipients and endogenous substances from the plasma samples

[Examination of the change in plasma concentration of OH-flutamide in low-dose flutamide (250 mg/day) monotherapy for prostate cancer patients].

An examination of the change in plasma concentration of OH-flutamide in low-dose flutamide (250 mg/day) monotherapy for 5 prostate cancer patients was performed. We treated 5 patients diagnosed with prostate cancer between September and November 2002. The plasma concentrations of OH-flutamide, PSA and AST/ALT were measured before and after low-dose flutamide monotherapy was started. The plasma concentrations of OH-flutamide were stable in the third day after medication was started, and even when compared with the plasma concentrations of OH-flutamide 375 mg/day, there was no significant difference. Although at the observation period was short, PSA fell favorably in all patients. The AST/ALT were in the normal range in all patients. The low-does flutamide therapy has been one of medical treatments if its safety and effectiveness has been demonstrated.

Metabolite profiles of flutamide in serum from patients with flutamide-induced hepatic dysfunction.

Hepatic dysfunction due to flutamide administration has been reported and this side effect often limits the use of the agent. The prediction of flutamide-induced hepatotoxicity is attributed to the proper use of the antiandrogen. In this study, we investigated whether hepatic dysfunction could be assessed by the metabolite profile in serum from patients receiving this drug. Serum samples were obtained from 15 patients with prostate cancer, 12 patients with no sign of hepatotoxicity and 3 patients with slight hepatic dysfunction during long-term flutamide treatment. We analyzed the metabolite profiles by LC/MS in selected ion monitoring mode and detected a new metabolite (M3) that was an oxidation product of flutamide. However, there were no consistent differences in the serum flutamide metabolites between patients with normal function and those suffering hepatic dysfunction. The metabolite profiles in the beta-glucuronidase-treated serum showed a similar pattern between normal functioning and dysfunctional groups. Thus, the profile of flutamide metabolites determined in serum may not contribute to the risk prediction of flutamide-related hepatotoxicity.

Flutamide-induced hepatic dysfunction in relation to steady-state plasma concentrations of flutamide and its metabolites.

The frequency, severity, and outcome of flutamide-induced hepatic injury were prospectively evaluated in 55 patients with prostate cancer who received 125 mg of flutamide 3 times a day (daily dose: 375 mg) combined with an agonistic analogue of luteinizing hormone-releasing hormone. In addition, we examined plasma and urine concentrations of flutamide and its major metabolites 4 weeks after the beginning of flutamide therapy, and evaluated their significance in predicting flutamide-induced hepatic dysfunction. Hepatic function could be assessed in 50 patients and hepatic dysfunction during therapy was observed in 9 patients (18%); 3 patients (6%) were classified as having moderate liver dysfunction and 6 (12%) were classified as having mild liver dysfunction. The steady-state plasma levels of flutamide and its biologic active metabolite, hydroxyflutamide (OH-Flu), were not related to hepatic dysfunction. However, the concentration of another major metabolite, 4-nitro-3-(trifluoromethyl)phenylamine (FLU-1) was considerably higher in 2 patients who developed clinically significant hepatic dysfunction. These findings suggest that clinically significant hepatic dysfunction could be induced in patients with compromised flutamide metabolism, which leads to a high concentration of FLU-1. Based on results of this study, we propose that plasma FLU-1 levels are one of the predictive factors for flutamide-induced hepatic dysfunction. This hypothesis will be confirmed in a large-scale study.

Hydroxypropyl-beta-cyclodextrin-flutamide inclusion complex. II. Oral and intravenous pharmacokinetics of flutamide in the rat.

PURPOSE: The objective of this work was to determine the pharmacokinetics of flutamide (FLT) and its active metabolite, 2-hydroxy-flutamide (FLT-2-OH) in rats, following formulation in hydroxypropyl-Beta-cyclodextrin (FLT-HPBetaCyD). METHODS: The pharmacokinetics of FLT-HPBetaCyD, FLT-suspension (FLT-SUSP), and FLT-solution (FLT-COSOLV) were compared after oral (p.o.) and intravenous (i.v.) administration, respectively. In a non-crossover design, male Sprague-Dawley rats received each formulation as a single oral dose [15 mg (54 micro mol) FLT/kg] by oral gavage, or single i.v. dose [1.6 mg (5.8 micro mol) FLT/kg] via an indwelling jugular vein catheter. FLT and its metabolite, FLT-2-OH, were determined in plasma and urine aliquots by an HPLC method. RESULTS: In a preliminary in vitro experiment, using the dialysis bag dissolution method, 80% of a test dose of FLT was released from lyophilized FLT-HPBetaCyD into simulated gastric juice within 2 h, compared to less than 5% release from commercial FLT powder (FLT-SUSP). Following oral FLT-HPBetaCyD, the mean area under the plasma concentration curve (AUC(0- infinity)) for FLT, was 1580 +/- 228 ng x h/mL, with the maximum plasma concentration (Cmax; 1297 +/- 127 ng/mL) at 0.5 h (Tmax) after administration. The AUC(0- infinity) and C(max) were significantly higher than after FLT-SUSP (AUC(0- infinity) 748 +/- 206 ng x h/mL; C(max) 230 +/- 111 ng/mL and T(max) 2.33 +/- 0.29 h, respectively). After i.v. FLT-HPBetaCyD, the FLT AUC(0- infinity) was 1355 +/- 162 ng x h/mL, compared to 1421 +/- 283 ng x h/mL for FLT-COSOLV. FLT C(max) were 714 +/- 144 mL/h and 735 +/- 88 mL/h, respectively. The respective volumes of distribution (V(z)) were 369 +/- 191 mL and 242 +/- 25 mL. The plasma concentration-time profile and pharmacokinetic parameters of FLT after FLT-HPBetaCyD and FLT-COSOLV did not differ significantly. The pharmacokinetic parameters for FLT-2-OH were formulation independent after i.v. dosing, but AUC(0- infinity); C(max) and T(max), values were substantially greater with the FLT-HPBetaCyD in the oral study (40269 +/- 5875 ng x h/mL, 4062 +/- 502 ng/mL, and 3.50 +/- 0.41 h, respectively). CONCLUSIONS: FLT from FLT-HPBetaCyD was released rapidly into solution in vitro and in vivo. FLT-HPBetaCyD improved oral bioavailability relative to FLT-SUSP. Intravenous pharmacokinetic profiles for both FLT and FLT-2-OH were identical following either FLT-HPBetaCyD or FLT-COSOLV, indicating that the FLT-HPBetaCyD formulation behaved as a true solution.

Determination of 2-hydroxyflutamide in human plasma by high-performance liquid chromatography and its application to pharmacokinetic studies.

Flutamide is a potent antiandrogen used for the treatment of prostatic cancer. Flutamide undergoes extensive first-pass metabolism to the pharmacologically active metabolite 2-hydroxyflutamide. A simple, sensitive, precise, accurate and specific HPLC method, using carbamazepine as the internal standard, for the determination of 2-hydroxyflutamide in human plasma was developed and validated. After addition of the internal standard, the analytes were isolated from human plasma by liquid-liquid extraction. The method was linear in the 25 to 1,000 ng/ml concentration range (r>0.999). Recovery for 2-hydroxyflutamide was greater than 91.4% and for internal standard was 93.6%. The limit of quantitation was 25 ng/ml. Inter-batch precision, expressed as the relative standard deviation (RSD), ranged from 4.3 to 7.9%, and accuracy was better than 93.9%. Analysis of 2-hydroxyflutamide concentrations in plasma samples from 16 healthy volunteers following oral administration of 250 mg of flutamide provided the following pharmacokinetic data (mean+/-SD): Cmax, 776 +/- 400 ng/ml; AUC(0-infinity), 5,368 +/- 2,689 ng h/ml; AUC(0-t) 5,005 +/- 2,605 ng h/ml; Tmax 2.6 +/- 1.6 h; elimination half-life, 5.2 +/- 2.0 h.

Dissolution rate limited bioavailability of flutamide, and in vitro - in vivo correlation.

Flutamide is due to its properties as a practically water-insoluble, high-dose drug substance a typical representative of a drug with particle size limited dissolution rate and bioavailability. An in vitro dissolution test method comprising of standard paddle stirrer, round-bottomed vessel of 4 l capacity, and 0.1 N hydrochloric acid with 0.5% of sodium lauryl sulphate as dissolution medium, was developed. The dissolution method was shown discriminatory and predictive regarding bioavailability of conventional 250 mg flutamide tablets with different in vitro dissolution rates. Relative bioavailability of flutamide from the tablets, determined as AUC of the active metabolite 2-hydroxyflutamide in healthy male subjects, could be correlated with drug amount dissolved during 45 min in the in vitro test. Also bioavailability data from four different biostudies could be compared utilising the calculated ratios R(AUC) and R(Diss.) for the test and reference formulations in the individual studies. It is suggested that the concept of R(AUC) and R(Diss.) can also be applied to other orally administered, poorly soluble, high-dose drug substances with dissolution rate limited bioavailability.

[Serum concentrations of flutamide and goserelin in a prostate cancer patient with obstructive nephropathy: a case report].

A 72-year-old man presented with pollakiuria and dysuria. His prostate was the size of an apple and hard on digital rectal examination and the serum prostate specific antigen (PSA) level was 73 ng/ml (RIA). Ultrasonography revealed bilateral hydronephrosis and the serum creatinine level was 13.2 mg/dl. CT scanning of the abdomen demonstrated swelling of paraaortic lymph nodes. Transrectal needle biopsy of the prostate gave a diagnosis of moderately differentiated adenocarcinoma. Accordingly, the final diagnosis was prostate cancer (cT3N4M1, stage D2). Immediately after bilateral percutaneous nephrostomy, treatment with an LH-RH agonist (goserelin) and flutamide was commenced. Serum creatinine was 6.6 mg/dl at the start of antiandrogen therapy and decreased to 1.8 mg/dl after 27 days. A 125 mg flutamide capsule was administered at 7 a.m., and blood samples were collected 4 hours later on days 1, 2, 3, 5, 6, 8, 12, 14, 17, 18 and 27. The OH-flutamide concentration was measured. There was no significant correlation between serum creatinine and the OH-flutamide concentration. After implantation of goserelin (3.6 mg depot), blood samples were obtained at 11 a.m. on days 8, 12, 14, 15 and 25. The serum goserelin level was measured. The serum goserelin level increased to a peak on day 14, as described previously, but the peak value of 9.63 ng/ml was higher than that reported before (mean +/- SD 2.848 +/- 0.199).

[Flutamide-induced hepatic disorder and serum concentrations of flutamide and its metabolites in patients with prostate cancer].

Severe hepatotoxicity occurred in a prostate cancer patient treated with 375 mg of flutamide per day, 125 mg three times a day, for 11 weeks. Serial measurements of serum concentrations of flutamide and its metabolites in the patient showed an unusually high serum level and delayed elimination of flutamide and suggested decreased metabolic activity of oxidation of flutamide to OH-flutamide. In 37 patients with prostate cancer we periodically monitored the serum concentrations of flutamide as well as liver function parameters. In 2 patients, glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) elevated over 100 IU/L, and treatment with flutamide was discontinued. Slight elevation of GOT and GPT over 40 to 100 IU/L was also detected in 5 patients, and flutamide was withdrawn. The elevated GOT and GPT in these 7 patients recovered to the pretreatment levels after discontinuation of the treatment. In these patients with flutamide-induced hepatic disorders, the average serum concentration of flutamide was higher (2.76 times, and that of OH-flutamide was lower (0.76 times), as compared with patients who maintained normal liver function.