Stir bar sorptive-dispersive microextraction for trace determination of triphenyl and diphenyl phosphate in urine of nail polish users.

This work describes a new analytical method useful for monitoring the human exposure to the endocrine-disrupting plasticizer triphenyl phosphate (TPP) via nail polish use. The method allows trace determination of this parent compound and its main metabolite, namely diphenyl phosphate (DPP), in urine samples of nail polish users. The method is based on a novel microextraction technique termed stir bar sorptive-dispersive microextraction (SBSDME) using a magnetic composite made of CoFe2O4 magnetic nanoparticles embedded into a mixed-mode weak anion exchange polymer (Strata™-X-AW), followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The main parameters involved in the extraction procedure were evaluated and optimized. Under the optimized conditions, the method was successfully validated showing good linearity (at least up to 100 ng mL-1) and enrichment factors (17 and 30), limits of detection and quantification in the low ng L-1 range (1.9-17.1 ng L-1 and 6.3-57.1 ng L-1, respectively) and good intra- and inter-day precision (RSD < 8%). Excellent recoveries (81-112 %) were achieved by using matrix-matched calibration for quantification. Finally, the method was applied to the determination of both the parent compound and the metabolite in human urine samples from volunteers who applied themselves a nail polish containing TPP. Detectable amounts of the parent compound were found just in the first urination, whereas quantifiable amounts of DPP were found in the low ng mL-1 range even 24 h after application of the nail polish, thus suggesting a rapid biotransformation and a low excretion, and showing DPP as excellent biomarker of human exposure to TPP. This work expands the analytical potential of the novel SBSDME, and the proposed methodology contributes to the study of the absorption/excretion levels of endocrine disruptors present in cosmetic products.

Applicability of in vitro-in vivo translation of cathepsin K inhibition from animal species to human with the use of free-drug hypothesis.

The correlation of in vitro inhibition of cathepsin K (CatK) activity and in vivo suppression of collagen I biomarkers was examined with three selective CatK inhibitors to explore the potential translatability from animal species to human. These inhibitors exhibited good in vitro potencies toward recombinant CatK enzymes across species, with IC50 values ranging from 0.20 to 6.1 nM. In vivo studies were conducted in animal species following multiple-day dosing of the CatK inhibitors to achieve steady-state plasma drug concentration-time profiles. Measurement of urinary bone resorption biomarkers (cross-linked N-terminal telopeptide and helical peptide of type I collagen) revealed drug concentration-dependent suppression of biomarkers, with EC50 values estimated to be 12 to 160 nM. Marked improvement in the correlation between in vitro and in vivo CatK activities was observed with the application of unbound (free) fraction in plasma, consistent with the conditions stipulated by the free-drug hypothesis. These results indicate that the in vitro-in vivo translation of CatK inhibition observed in animal species can translate to humans when the unbound fraction of the inhibitor is considered. Interestingly, residual levels of urinary bone resorption marker were detected as the suppression reached saturation (at an average of 82% inhibition), an apparent phenomenon observed regardless of the species, biomarker, or compound examined. Since cathepsin enzymes other than CatK were reported to catalyze cleavage of collagen I, it is hypothesized that CatK-mediated degradation of collagen I in bone represents ~82% of overall collagen I turnover in the body.

Vitamin D-Binding Protein Is a Potential Urinary Biomarker of Irbesartan Treatment Response in Patients with IgA Nephropathy.

AIMS: The purpose of this study was to identify predictive markers of irbesartan (an angiotensin receptor blocker) treatment response in immunoglobulin A nephropathy (IgAN) patients. METHODS: Urine samples were collected both before and after irbesartan treatment in IgAN patients and compared with urine from healthy volunteers. The total urinary protein produced in 24 h was measured to determine therapeutic response. The urinary proteome was evaluated by two-dimensional gel electrophoresis coupled with MALDI-TOF-MS/MS analysis. Western blotting was used to verify protein expression. A receiver operating characteristic curve was used to evaluate the sensitivity and specificity of candidate biomarkers. RESULTS: Four differentially expressed proteins were identified as vitamin D-binding proteins (VDPs). Western blot showed that urinary VDPs were significantly elevated in nonresponsive versus responsive IgAN patients. The sensitivity, specificity, and accuracy of urinary VDP as a predictive biomarker of irbesartan nonresponsiveness in IgAN were 65%, 85%, and 75%, respectively. CONCLUSION: Our results revealed that urinary VDP might be a useful biomarker for predicting irbesartan treatment response.

Rapid determination of nine parabens and seven other environmental phenols in urine samples of German children and adults.

We developed a fast, selective and sensitive on-line LC/LC-MS/MS method for the simultaneous determination of nine parabens and seven environmental phenols in urine. Parabens are widely used as antimicrobial preservatives. Bisphenol A, triclosan, triclocarban, 2-phenylphenol, and benzophenones are used inter alia in disinfectants, sunscreens and in polymers. Some of these substances are suspected endocrine disruptors. Limits of quantification and analytical quality criteria fully met the needs for determining exposure levels occurring in the general population. We analyzed 157 spot urine samples from the general German population (59 females, 39 males and 59 children). For the parabens, we found methyl, ethyl and n-propyl paraben with high detection rates (77-98%), followed by n-butyl (36%), iso-butyl (17%), iso-propyl (3%) and benzyl paraben (3%). We detected no pentyl and heptyl paraben. Urinary concentrations were highest for methyl paraben (median 24.5 µg/L; 95th percentile 379 µg/L) followed by ethyl (1.4 µg/L; 35.2 µg/L) and n-propyl paraben (1.2 µg/L; 68.1 µg/L). Other environmental phenols with high detection rates were BPA (95%), triclosan (45%) and benzophenone 1 and 3 (26%). For most of the parabens/environmental phenols we found higher urinary levels in females than in males or children, probably due to differences in (personal care) product use. However, high levels (in the mg/L range) were also observed in children. Exposure to the above substances is occurring worldwide. Differences between countries do seem to exist and might be caused by different product compositions or different use habits. Human metabolism data is urgently needed to extrapolate from urinary biomarker levels to doses actually taken up.

A novel dilute and shoot HPLC assay method for quantification of irbesartan and hydrochlorothiazide in combination tablets and urine using second generation C18-bonded monolithic silica column with double gradient elution.

Irbesartan (IRB) and hydrochlorothiazide (HCT) are angiotensin-II receptor antagonist and thiazide-class diuretic compounds, respectively, which are in use in the treatment of hypertension. A novel dilute-and-shoot HPLC assay method for simultaneous quantification of IRB and HCT in fixed-dose combination tablets and urine samples was described. The separation of IRB, HCT and agomelatine (internal standard) was carried out using a second generation C18-bonded monolithic silica column (Chromolith(®) High Resolution RP-18e, 100×4.6mm, Merck KGaA), utilizing both mobile phase and flow rate gradient elution programs. The analytes were detected at 230 nm wavelength using photodiode array detector within 24 minutes with high resolution, observing about 50 percent more peak capacity when using second generation C18-bonded monolithic silica column. Urine samples were introduced into the system effortlessly, with only filtration and subsequent dilution. Validation studies were performed according to the official recommendations of USP and ICH, and the developed method was successfully applied to pharmaceutical tablets and urine samples.

Absorption, distribution, metabolism, and excretion (ADME) of ¹4C-sonidegib (LDE225) in healthy volunteers.

PURPOSE: The absorption, distribution, metabolism, and excretion of the hedgehog pathway inhibitor sonidegib (LDE225) were determined in healthy male subjects. METHODS: Six subjects received a single oral dose of 800 mg ¹4C-sonidegib (74 kBq, 2.0 µCi) under fasting conditions. Blood, plasma, urine, and fecal samples were collected predose, postdose in-house (days 1-22), and during 24-h visits (weekly, days 29-43; biweekly, days 57-99). Radioactivity was determined in all samples using accelerator mass spectrometry (AMS). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine concentrations of sonidegib and its main circulating metabolite in plasma. Metabolite profiles and structures were determined in pooled plasma, urine, and fecal samples using high-performance LC-AMS and LC-MS/MS, respectively. RESULTS: A single dose of ¹4C-sonidegib was well tolerated in healthy subjects. Unchanged sonidegib and total radioactivity reached peak concentration in plasma by 2 and 3 h, respectively, and demonstrated similarly long half-lives of 319 and 331 h, respectively. Absorbed sonidegib (estimated 6-7 %) was extensively distributed, and the approximate terminal volume of distribution was 2,500 L. Unchanged sonidegib and a metabolite resulting from amide hydrolysis were the major circulating components (36.4 and 15.4 % of radioactivity area under the curve, respectively). Absorbed sonidegib was eliminated predominantly through oxidative metabolism of the morpholine part and amide hydrolysis. Unabsorbed sonidegib was excreted through the feces. Metabolites in excreta accounted for 4.49 % of the dose (1.20 % in urine, 3.29 % in feces). The recovery of radioactivity in urine and feces was essentially complete (95.3 ± 1.93 % of the dose in five subjects; 56.9 % of the dose in one subject with incomplete feces collection suspected). CONCLUSIONS: Sonidegib exhibited low absorption, was extensively distributed, and was slowly metabolized. Elimination of absorbed sonidegib occurred largely by oxidative and hydrolytic metabolism.

Disposition and metabolism of the cathepsin K inhibitor odanacatib in humans.

Odanacatib is a selective inhibitor of the cathepsin K enzyme that is expressed in osteoclasts involved in the degradation of bone organic matrix, and is being developed as a novel treatment of osteoporosis. Odanacatib has demonstrated increases in bone mineral density in postmenopausal women and is undergoing a pivotal phase III trial. The absorption, metabolism, and excretion of [(14)C]odanacatib were studied in healthy male volunteers (n = 6) after a single oral dose of 25 mg (100 µCi). Plasma, urine, and fecal samples were collected at intervals up to 34 days postdose. The pharmacokinetics of odanacatib were characterized by slow absorption (mean time to achieve maximum plasma concentration of 14.2 hours) and long apparent elimination half-life (mean t1/2 96.7 hours); 74.5% of the dose was recovered in feces and 16.9% in urine, resulting in a total recovery of 91.4%. Seven metabolites were identified in urine; the major pathway (methyl hydroxylation producing M8 and its derivatives) was largely dependent on CYP3A. Metabolites and odanacatib accounted for 77% and 23% of urinary radioactivity, respectively. In fecal extracts, the only radioactive components identified were odanacatib (60.9%) and M8 (9.5%). The fraction of odanacatib in feces derived from absorbed drug was estimated using a bioavailability value obtained from the results of a separate intravenous study. Collectively, the data indicate that odanacatib has a long t1/2 on account of its low metabolic intrinsic clearance, and that metabolism (principally mediated by CYP3A) and excretion of intact parent compound account for ∼70% and ∼30% of the clearance of odanacatib in humans.

Sulfate conjugates are urinary markers of inhalation exposure to 4-chlorobiphenyl (PCB3).

PCBs are contaminants in the air of older buildings and cities, which raises the concern of inhalation exposure. No reliable biomarker of such exposure is available. We exposed rats to air containing 2 mg/m(3) PCB3 via nose-only inhalation for 2 h, collected urine, and analyzed it by LC/MS. Each rat inhaled an estimated dose of 35 µg PCB3, and excreted 27 ± 2% of it as sulfates within 24 h. Peak excretion occurred within 6 h. PCB sulfates were stable in urine for at least three days at room temperature without chemical preservatives. These data support the use of PCB sulfate conjugates as suitable urinary biomarkers of PCB3 and other airborne PCBs.

Ionic liquids dispersive liquid-liquid microextraction and high-performance liquid chromatographic determination of irbesartan and valsartan in human urine.

An environmentally friendly ionic liquids dispersive liquid-liquid microextraction (IL-DLLME) method coupled with high-performance liquid chromatography (HPLC) for the determination of antihypertensive drugs irbesartan and valsartan in human urine samples was developed. The HPLC separations were accomplished in less than 10 min using a reversed-phase C(18) column (250 × 4.60 mm i.d., 5 µm) with a mobile phase containing 0.3 % formic acid solution and methanol (v/v, 3:7; flow rate, 1.0 mL/min). UV absorption responses at 236 nm were linear over a wide concentration range from 50 µg/mL to the detection limits of 3.3 µg/L for valsartan and 1.5 µg/L for irbesartan. The effective parameters on IL-DLLME, such as ionic liquid types and their amounts, disperser solvent types and their volume, pH of the sample and extraction time were studied and optimized. The developed IL-DLLME-HPLC was successfully applied for evaluation of the urine irbesartan and valsartan profile following oral capsules administration.

Identification of sulfated metabolites of 4-chlorobiphenyl (PCB3) in the serum and urine of male rats.

Polychlorinated biphenyls (PCBs) are legacy pollutants that exert toxicities through various mechanisms. In recent years exposure to PCBs via inhalation has been recognized as a hazard. Those PCBs with lower numbers of chlorine atoms (LC-PCBs) are semivolatile and have been reported in urban air, as well as in the indoor air of older buildings. LC-PCBs are bioactivated to phenols and further to quinone electrophiles with genotoxic/carcinogenic potential. We hypothesized that phenolic LC-PCBs are subject to conjugation and excretion in the urine. PCB3, often present in high concentrations in air, is a prototypical congener for the study of the metabolism and toxicity of LC-PCBs. Our objective was to identify metabolites of PCB3 in urine that could be potentially employed in the estimation of exposure to LC-PCBs. Male Sprague-Dawley rats (150-175 g) were housed in metabolism cages and received a single intraperitoneal injection of 600 µmol/kg body weight of PCB3. Urine was collected every 4 h; rats were euthanized at 36 h; and serum was collected. LC/MS analysis of urine before and after incubation with ß-glucuronidase and sulfatase showed that sulfate conjugates were in higher concentrations than glucuronide conjugates and free phenolic forms. At least two major metabolites and two minor metabolites were identified in urine that could be attributed to mercapturic acid metabolites of PCB3. Quantitation by authentic standards confirmed that approximately 3% of the dose was excreted in the urine as sulfates over 36 h, with peak excretion occurring at 10-20 h after exposure. The major metabolites were 4'PCB3sulfate, 3'PCB3 sulfate, 2'PCB3 sulfate, and presumably a catechol sulfate. The serum concentration of 4'PCB3 sulfate was 6.18 ± 2.16 µg/mL. This is the first report that sulfated metabolites of PCBs are formed in vivo. These findings suggest a prospective approach for exposure assessment of LC-PCBs by analysis of phase II metabolites in urine.

Assessment of the drug-drug interactions between fimasartan and hydrochlorothiazide in healthy volunteers.

AIM: Fimasartan is a selective angiotensin II receptor blocker. Hydrochlorothiazide (HCTZ), which is used to treat hypertension and edematous conditions, is coadministered with many antihypertensive agents. METHODS: An open-label, randomized, multiple-dosing, 2-arm, 1-sequence, 2-period study was conducted to assess the effects of fimasartan (240 mg) on HCTZ (25 mg) or vice versa in 18 and 14 healthy male volunteers, respectively. During each drug administration period, drugs were given once daily for 7 days, with a 7-day washout period between the 2 administration periods. RESULTS: The respective geometric mean ratios of fimasartan for AUC τ,ss and C max,ss with HCTZ were 1.30 [90% confidence interval (CI), 0.84-2.01] and 1.17 (90% CI, 0.93-1.47) compared with fimasartan alone. The respective geometric mean ratios of HCTZ for AUC τ,ss and C max,ss with fimasartan were 0.94 (90% CI, 0.84-1.04) and 0.88 (90% CI, 0.80-0.97) compared with HCTZ alone. Plasma renin activity indicated no significant differences between fimasartan monotherapy and coadministered treatment. CONCLUSIONS: Fimasartan administered alone or in combination with HCTZ was well tolerated at the described dosages. Coadministration of fimasartan increased the urinary excretion of HCTZ and urine volume, but these observations are unlikely to have any clinical relevance.

Safety, tolerability, pharmacokinetics, and pharmacodynamics of fimasartan following single and repeated oral administration in the fasted and fed states in healthy subjects.

BACKGROUND AND OBJECTIVES: Fimasartan (BR-A-657) is a novel, non-peptide angiotensin II receptor antagonist with a selective type I receptor blockade effect. Two first-in-human studies investigated the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of fimasartan. METHODS: Fasted single oral tablet doses of fimasartan 20-480 mg or placebo were administered to 40 healthy male subjects (aged 19-54 years) in a double-blind, randomized, sequential-group design. Subjects receiving fimasartan 240 mg also received the same treatment in the fed state after an interval of 7 days. In another study, oral tablet doses of fimasartan 120 and 360 mg or placebo were given once daily for 7 days to groups of eight fasted healthy male subjects (aged 20-55 years) in a double-blind, randomized, sequential-group design. Safety and tolerability were assessed. The PK and PD of fimasartan were also evaluated and compared for the different doses. RESULTS: Fimasartan was safe and well tolerated, but with an increased incidence of low BP and postural dizziness for the 360 mg dose after repeated administration. Fimasartan produced increases in plasma renin activity, angiotensin I and II, which were not dose dependent. Maximal increases occurred between 6 and 8 hours post-dose, lasting up to 48 hours. Fimasartan was absorbed rapidly after all doses and had a multiphasic distribution. Two peaks in the plasma concentration-time profile were observed in most subjects. Steady state was achieved after three doses, and accumulation was minimal after repeated doses for 7 days (24-30%). The effective half-life ranged from 9.84 to 13.2 hours. The systemic exposure of fimasartan was dose proportional, and no marked food effect was noted after administration of 240 mg in the fed state. Urinary excretion of fimasartan was very low (1.74-2.51%), suggesting non-renal elimination. CONCLUSION: Fimasartan had a good safety profile and was well tolerated after fasted single oral doses of 20-480 mg, a fed single oral dose of 240 mg, and fasted repeated oral doses of 120 and 360 mg in healthy subjects. In addition, the PK and PD of fimasartan in this population were well characterized. Further studies are needed to evaluate the safety, efficacy, and dose-response relationship of fimasartan in patients with hypertension.

Novel use of a whole cell E. coli bioreporter as a urinary exposure biomarker.

Bacterial bioreporters have substantial potential for contaminant assessment but their real world application is currently impaired by a lack of sensitivity. Here, we exploit the bioconcentration of chemicals in the urine of animals to facilitate pollutant detection. The shore crab Carcinus maenas was exposed to the organic contaminant 2-hydroxybiphenyl, and urine was screened using an Escherichia coli-based luciferase gene (luxAB) reporter assay specific to this compound. Bioassay measurements differentiated between the original contaminant and its metabolites, quantifying bioconcentration factors of up to one hundred-fold in crab urine. Our results reveal the substantial potential of using bacterial bioreporter assays in real-time monitoring of biological matricesto determine exposure histories, with wide ranging potential for the in situ measurement of xenobiotics in risk assessments and epidemiology.

Separation and quantitation of several angiotensin II receptor antagonist drugs in human urine by a SPE-HPLC-DAD method.

In this work, an SPE-HPLC method coupled to photodiode array detection was validated in human urine matrix, in order to monitor four antihypertensive angiotensin II receptor antagonist drugs in patients under cardiovascular treatment. For that purpose, experimental design was used. Quantitation was accomplished by the internal standard method. The obtained LOQs were 95, 113, 125, and 85 ng/mL for eprosartan, telmisartan, irbesartan, and valsartan, respectively. The intraday and interday precision and accuracy at four concentration levels in the working range (LOQ-15 microg/mL) were always lower than 11% RSD and 8% relative error. The urine samples proved to be stable during 4 h at room temperature, after three thaw-freeze cycles, and for 2 months at -20 degrees C. No interferences from other endogenous compounds or co-administered drugs were found. The method has been successfully applied to monitor the renal elimination of eprosartan and valsartan during 24 h.

Novel polymer monolith microextraction using a poly(methacrylic acid-ethylene glycol dimethacrylate) monolith and its application to simultaneous analysis of several angiotensin II receptor antagonists in human urine by capillary zone electrophoresis.

Novel polymer monolith microextraction (PMME) using a poly(methacrylic acid-ethylene glycol dimethacrylate) (poly(MAA-EGDMA)) monolith in conjunction with capillary zone electrophoresis (CZE) was developed for the determination of several angiotensin II receptor antagonists (ARA-IIs) in human urine. The extraction device consisted of a regular plastic syringe (1 mL), a poly(MAA-EGDMA) monolithic capillary (2 cm x 530 microm I.D.) and a plastic pinhead connecting the former two components seamlessly. The extraction was achieved by driving the sample solution through the monolithic capillary tube using a syringe infusion pump, and for the desorption step, an aliquot of organic solvent was injected via the monolithic capillary and collected into a vial for subsequent analysis by CZE. The best separation was realized at 25 kV using a buffer that consisted of 50% acetonitrile and 50% buffer solution (v/v) containing 10 mM disodium hydrogenphosphate (adjusted to pH 2.3 with 1M hydrochloric acid). The method was successfully applied to the determination of telmisartan (T), irbesartan (I) and losartan (L) in urine samples with candesartan (C) as internal standard, yielding the detection limit of 15-20 ng/mL. Close correlation coefficients (R>0.999) and excellent method reproducibility were obtained for all the analytes over a linear range of 0.08-3 microg/mL.

Evaluation of 18F-FA-4 and 11C-pipzA-4 as radioligands for the in vivo evaluation of the high-affinity choline uptake system.

UNLABELLED: 4,4'-Bis-1-hydroxy-2-(4-methylpiperidin-1-yl)ethyl-biphenyl (A-4), a tertiary amine analog of hemicholinium-3 (HC-3), is an inhibitor of the sodium-dependent high-affinity choline uptake (HACU) system. We have evaluated 4-[1-hydroxy-2-(4-(18)F-fluoromethylpiperidin-1-yl)ethyl]-4'-[1-hydroxy-2-(4-methylpiperidin-1-yl)ethyl]biphenyl ((18)F-FA-4) and 4-[1-hydroxy-2-(4-(11)C-methylpiperazin-1-yl)ethyl]-4'-[1-hydroxy-2-(4-methylpiperidin-1-yl)ethyl]biphenyl ((11)C-pipzA-4), an (18)F- and a (11)C-labeled derivative of A-4 as potential in vivo tracers for the HACU system. METHODS: The biodistribution of both compounds was determined in mice, and the intracerebral distribution was visualized by ex vivo and in vitro autoradiography. The in vitro affinity of the compounds was determined by a displacement study with (3)H-HC-3 on mice brain slices. RESULTS: In mice, both tracers show a high and persistent brain uptake. In vitro autoradiography shows binding to the striatum, whereas ex vivo autoradiography shows homogeneous binding throughout the brain. FA-4 and pipzA-4 inhibited the (3)H-HC-3 binding with a 50% inhibitory concentration of 57 nmol/L and 320 nmol/L, respectively. CONCLUSION: The evaluated compounds have affinity for HACU and show high uptake in the brain. In vitro binding of the compounds to the striatum cannot be inhibited by the presence of HC-3, whereas binding of HC-3 was inhibited by the presence of both FA-4 and pipzA-4, suggesting allosteric binding.

Mechanism of urinary tract crystal formation following biphenyl treatment.

Coadministration of biphenyl and KHCO3 in the diet of male rats for 13 weeks produced urine crystals, which, by means of LC-MS/MS analyses, were determined to be composed of the potassium salt of 4-hydroxy-biphenyl-O-sulfate (4-HBPOSK). Biphenyl alone or biphenyl with KCl or NaHCO3 in the diet did not produce urine crystals. It was found that the higher concentration of potassium in the urine and the alkaline pH induced by feeding KHCO3 to rats resulted in the formation of urine crystals of 4-HBPOSK due to 4-HBPOSK solubility being lower in urine than in plasma. Urine crystals of 4-HBPOSK produced hyperplasia of the transitional epithelium of the ureter, ureteral obstruction, and hydronephrosis in the urinary tract.

[Simultaneous determination of magnolol and honokiol in serum and urine by high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic method for simultaneous determination of magnolol and honokiol in serum and urine of rat has been established. Two drugs were determined within 15 minutes by the method on the column with spherisorb C18, by using a mobile phase consisted of methanol-water-glacial acetic acid (70:30:1, V/V) at 1 mL/min, monitored at 294 nm and with a sensitivity of 0.005 AUFS. After 0.25, 1 and 8 hour of administration of the drugs, protein in serum and urine of Wistar rat was precipitated by methanol and magnolol and honokiol in acidified body fluid were determined after being extracted by a mixture of ethyl acetate and ether. Good linear relationship between concentration in serum and urine and peak area in the ranges of 0.05-2 mg/L for magnolol and 0.025-1 mg/L for honokiol was obtained. Good precision and reproducibility were found too. The average recoveries of the two drugs were 95.6% (RSD = 3.85%), 93.8% (RSD = 3.95%) in serum and 96.0% (RSD = 3.83%), 94.9% (RSD = 3.54%) for urine respectively. The lower limit of the method was 0.02 mg/L of magnolol and 0.04 mg/L of honokiol respectively. The results showed that this method is suitable for the determination of magnolol and honokiol in body fluids.

Disposition of irbesartan, an angiotensin II AT1-receptor antagonist, in mice, rats, rabbits, and macaques.

Metabolism and disposition of irbesartan, an angiotensin II AT(1) receptor antagonist, were investigated in mice, rats, rabbits, and macaques. In both rats and macaques, irbesartan was characterized by a rapid oral absorption, a large volume of distribution, a low plasma clearance, and a long terminal half-life. The oral bioavailability in macaques was notably higher than in rats. Irbesartan was highly protein bound in rats and macaques. A lower binding rate was found in mice and rabbits. In distribution studies performed in rats, mice, and rabbits, irbesartan was rapidly distributed into most organs and tissues including brain, intrauterine area, and milk. No retention of radioactivity in tissues other than liver and kidney was noted. Irbesartan was the main circulating compound in rats, rabbits, and macaques representing a maximum of 67, 68, and 80% of plasma radioactivity, respectively. The drug was metabolized mainly by glucuronidation (primarily on the tetrazole ring), hydroxylation, and additional oxidation. The overall pathways within the different species generated 18 metabolites identified from bile, urine, and feces samples. Irbesartan did not significantly induce or inhibit most of the isoenzymes commonly associated with drug metabolism in either rats or macaques after oral administration for 1 month. In most species irbesartan and its metabolites were mainly excreted in feces with more than 80% of a radioactive dose recovered within 24 or 48 h. Enterohepatic circulation was demonstrated in rats and macaques.

Determination of candesartan cilexetil, candesartan and a metabolite in human plasma and urine by liquid chromatography and fluorometric detection.

Liquid chromatographic methods are described for the determination of a new effective anti-hypertensive drug candesartan (CV-11974), its prodrug candesartan cilexetil (TCV-116) and a metabolite, CV-15959 in human plasma and urine. The assays comprise liquid-liquid extraction and separation on a phenyl column with fluorometric detection. The methods give absolute recoveries of 70, 83 and 78% for candesartan cilexetil, candesartan and CV-15959, respectively, and the limit of quantification is 5, 1 and 3 nM of plasma (RSD < 20%), respectively. The methods were applied to plasma and urine samples from biopharmaceutical and clinical studies in man.