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A highly sensitive, accurate, and robust LC-MS/MS method was developed and validated for the simultaneous determination of ornidazole (ODZ) and miconazole (MCZ) in rat plasma using metronidazole (MTR) as an internal standard (IS). The analyte and IS were extracted from plasma by precipitating protein with acetonitrile and were chromatographed. The mobile phase was acetonitrile and 0.1% formic acid (75:25 v/v). The total run time was 3 min, and the injection volume was 5.0 μL. Multiple reaction monitoring (MRM) mode was used, in which the transitions of m/z 417.10→m/z 160.90 for MCZ, m/z 220.10→m/z 127.90 for ODZ, and m/z 172.10→m/z 128.1 for IS were monitored. The linearity range of MCZ was 0.15 -- 250.0 ng/mL and 3.0-250.0 ng/mL for ODZ. The lower limits of quantification (LLOQ) were found to be 0.05 ng/mL for MCZ and 1.0 ng/mL for ODZ in rat plasma. Recoveries of MCZ ranged between 75.33% -- 94.25% and ODZ ranged between 75.33% -- 95.54%. The quality control sample accuracy and precision (intra-day and inter-day) were -1.25% to 1.68% and 3.01% to 6.44% for MCZ and -1.31% to 1.88% and 3.34% to 6.98% for ODZ, respectively. The analytes and IS were stable during all sample storage and analysis procedures. [ABSTRACT FROM AUTHOR]

1. The current investigation was to develop and validate the LC-MS/MS method in order to analyse the various pharmacokinetic parameters of S019-0385. A sensitive, selective, and robust LC-MS/MS approach was established and validated for measuring S019-0385 in female mice plasma and tissue, using optimal multiple reaction monitoring (MRM) transition m/z 488.25/329.12 on positive mode. On a Waters Symmetry Shield C18 column, the analyte was separated using acetonitrile and deionised water with formic acid within 6 min at 0.7 mL/min. Linearity (R2 ≥ 0.99) was observed across 0.195–100 ng/mL concentration range using linear least-squares regression. 2. Blood-to-plasma ratio and plasma protein drug binding (%) in mice and human was assessed and found to be less than 1 and >83%, respectively. Absolute bioavailability (%F) of S019-0385 in female Swiss mice was exhibited to be 6.90%. Percent dose excreted S019-0385 in unchanged form through urine and faecal was found to be less than 2% and 0.5%, respectively. 3. Following oral administration at 5 mg/kg, the concentration of S019-0385 in tissue distribution was found to be in the order of C small intestine > C bone > C lung > C spleen > C kidney > C liver > C heart > C brain. [ABSTRACT FROM AUTHOR]

Although liquid chromatography-tandem mass spectrometry is the gold standard analytical platform for the quantification of drugs, metabolites, and biomarkers in biological samples, it cannot localise them in target tissues. The localisation and quantification of drugs and/or their associated metabolites in target tissues is a more direct measure of local drug exposure, biodistribution, efficacy, and regional toxicity compared to the traditional substitute studies using plasma. Therefore, combining high spatial resolution imaging functionality with the superior selectivity and sensitivity of mass spectrometry into one analytical technique will be a valuable tool for targeted localisation and quantification of drugs, metabolites, and biomarkers in tissues. Mass spectrometry imaging (MSI) is a tagless analytical technique that allows for the direct localisation and quantification of drugs, metabolites, and biomarkers in biological tissues, and has been used extensively in pharmaceutical research. The overall goal of this current review is to provide a detailed description of the working principle of MSI and its application in pharmacokinetic studies encompassing absorption, distribution, metabolism, excretion, and toxicity processes, followed by a discussion of the strategies for addressing the challenges associated with the functional utility of MSI in pharmacokinetic studies that support drug development. [ABSTRACT FROM AUTHOR]

Lubiprostone, a derivative of prostaglandin E1, is the first chemical-type constipation treatment approved by FDA. Lubiprostone has low systemic exposure after oral administration. Therefore, it is recommended that 15-hydroxylubiprostone, which is a dominant active metabolite of lubiprostone, be used as the pharmacokinetic evaluation indicator. Due to the microdosage of the lubiprostone capsules, it is difficult to develop a highly sensitive bioanalytical method for 15-hydroxylubiprostone. In this study, a highly sensitive and selective liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) method has been established and fully validated for the quantification of 15-hydroxylubiprostone in human plasma, and the validated bioanalytical method has been applied to a pharmacokinetic study of lubiprostone capsules successfully. The pharmacokinetics of 15-hydroxylubiprostone were observed after fed administration in healthy Chinese volunteers. The Cmax and AUC0-t were 75.8 ± 57.6 pg/mL and 222 ± 68.0 pg·h/mL for 15-hydroxylubiprostone. This study investigated the pharmacokinetic properties of 15-hydroxylubiprostone under fed conditions in healthy Chinese volunteers and would provide clinical guidance for the application and further development of lubiprostone capsules. [ABSTRACT FROM AUTHOR]

Thonningianin A is an ellagitannin substance and displays multiple pharmacological activities. This study investigated the pharmacokinetic characteristics of thonningianin A after oral administration in rats using a fully validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method. A sensitive and selective LC-MS/MS assay was developed for quantifying thonningianin A. Eighteen Wistar rats were randomly divided into three groups (n = 6), which were given at a single dose of 10, 20, or 40 mg/kg thonningianin A by gavage. Blood samples (200 µL) were collected from the orbit vein at designated time points and analyzed using the LC-MS/MS method to measure the levels of thonningianin A. Thonningianin A and internal standard (IS) were eluted at 1.5 and ∼3.0 min, respectively. The selected reaction mode transitions monitored were m/z 873.2 > 300.3 and 819.3 > 610.6 for thonningianin A and the IS, respectively. The calibration range was 10–1200 ng/mL. The intra- and the inter-day accuracy and precision met the acceptance criteria. No carryover and matrix effect were observed. The plasma concentrations of thonningianin A increased rapidly after oral administration of three dosages and reached the mean peak concentrations (Cmax) within 0.61–0.83 h. Meanwhile, AUC0–t/AUC0–∞ of the three dosage groups was more than 89.0% (10 mg/kg), 95.7% (20 mg/kg), and 97.0% (40 mg/kg). The present method is the first report in terms of the simple precipitation procedure, high sensitivity, and high-throughput efficiency. This validated assay was successfully applied to determine the pharmacokinetic behaviours of thonningianin A in rats. This study should be helpful for providing references for understanding the action mechanism and further application of Penthorum chinense. [ABSTRACT FROM AUTHOR]

A high-performance liquid chromatography-tandem mass spectrometric method for the determination of free and total dabigatran in human plasma has been developed and validated using a stable labeled internal standard (IS) as dabigatran D4. The extraction of analyte and IS was accomplished by the solid-phase extraction technique. Chromatographic separations were achieved using Peerless basic C8 (150 × 4.6) mm, 5 µ column eluted at a flow rate of 1 mL/min with mobile phase Acetonitrile: 5 mM ammonium formate: Methanol and 0.2% formic acid (30:20:50, v/v/v). The run time of the method was about 2.5 min with elution times of dabigatran and dabigatran D4 at around 1.2 min. The multiple reaction monitoring transitions (Q1/Q3) were set at 472/289, 172 (m/z) for dabigatran, and 476/293 (m/z) for dabigatran D4. The calibration curves were linear (r2 ≥0.99) over the range of 1.04–406.49 ng/mL. The presented method was successfully employed in the analysis of pharmacokinetic studies with the added advantage of demonstrating the effect of co-administration of dabigatran with the proton pump inhibitor pantoprazole on bioavailability and pharmacokinetic characteristics. Re-analysis of incurred sample resulted in >98% compliance indicating good assay precision of target analytes. [ABSTRACT FROM AUTHOR]

A selective, sensitive, rapid, and stable liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed for the simultaneous quantification of chlorthalidone (CLT) and telmisartan (TEL) in rat plasma. Sample preparation involved liquid-liquid extraction by ethyl acetate. Analytes and internal standard (IS) were separated on Gemini C18 (50 x 4.6 mm, 5 μm) using a mixture of methanol-2 mM ammonium acetate (80:20 v/v) as the mobile phase at a flow rate of 0.4 mL/min. Hydrochlorothiazide (HCTZ) was used as an internal standard. Detection was carried out using Electrospray positive and negative ionization mass spectrometry using multiple reaction monitoring of the transition at m/z 515.90→276 for TEL and m/z 337.1→190.05 for CLT, m/z 296.1→205.3 for HCTZ respectively. For TEL and CLT, the method was linear (R2 ≥ 0.995) within the range of 6-1200 ng/mL and 3-600 ng/mL respectively. The retention time for TEL, CLT, and IS was found to be 3.65±0.03 min, 1.83±0.02 min, and 1.76±0.01 min. The mean recovery for both analytes and IS was greater than 70 %. The developed method was validated according to the USFDA guideline. The quantitative method was validated for specificity, linearity, accuracy, precision, recovery, dilution integrity, matrix effect, and analyte stability. The method was successfully applied to a pharmacokinetic study in rat plasma following oral administration. [ABSTRACT FROM AUTHOR]

This paper describes the determination of aminocaproic acid in human plasma by simple, sensitive, and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using aminocaproic D6 acid as the internal standard (ISD). Extraction of aminocaproic acid and ISD was achieved from 200 µL plasma through protein precipitation with acetonitrile. Acetonitrile and 5 mM ammonium acetate buffer in the ratio 60:40 was used as the mobile phase at the flow rate of 1.0 mL/min. The method was developed with a short chromatographic run time of 3.0 min using Ace phenyl column. The retention times of both analyte and ISD were found to be 1.50 ± 0.1 min. The quantification of the separated components was done in positive ion mode by Multiple Reaction Monitoring (MRM) with mass transitions from m/z 132.2 (parent ion) to m/z 79.2 (product ion) for aminocaproic acid and from m/z 138.2 (parent ion) to m/z 74.3 (product ion) for the ISD. The method was validated as per the USFDA guidelines. The linearity was established over the concentration range of 0.3-80 µg/mL with r²>0.98. The % recovery was 86.69 % and 98.29 %, respectively for aminocaproic acid and ISD. The inter- and intra- day accuracy and precision (%CV) were in the range of 100.91 to 103.80 % and 0.91 to 3.63 %, respectively. The developed method was successfully applied for pharmacokinetic study in twelve healthy adult male subjects under fasting conditions and the results were authenticated by performing incurred sample reanalysis. [ABSTRACT FROM AUTHOR]

The compound 20(S),25-epoxydammarane-3β,12β,24α-triol (24-hydroxy-panaxadiol or 24-OH-PD), isolated from the red Panax ginseng CA Meyer possesses anticancer activity. Our aim was to study the pharmacokinetic characteristics of 24-OH-PD, which is essential for pre-clinical research during the development of new drugs. In this study, a simple and sensitive ultra-performance liquid chromatography-mass spectrometry (LC-MS/MS) method was established and used for studying the pharmacokinetics, in vitro protein binding, tissue distribution, and elimination profiles of 24-OH-PD in rats. 24-OH-PD was characterized by linear pharmacokinetics in the dose range of 2.5–10 mg/kg and had relatively longer half-life (4.82–5.45 h) than the other ginsenosides. It had a wide tissue distribution profile in rats and was primarily distributed in the lung. Within 96 h of intravenous administration, 13.84% of 24-OH-PD was excreted out via feces and 0.02% via urine in its unchanged form. In conclusion, a simple LC-MS/MS method with high sensitivity and selectivity was established for the quantification of 24-OH-PD. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the bioequivalence of a generic empagliflozin tablet versus a brand-named empagliflozin tablet (Jardiance®) and evaluate the food effects on the pharmacokinetics (PK) of empagliflozin in healthy Chinese subjects. Forty-eight healthy volunteers were included in this randomized, open-label, crossover, two-period study (fasting: n = 24, fed: n = 24). A single dose of 25-mg generic (or test) or brand-named (or reference) empagliflozin was administered to each subject in a randomized sequence. Blood samples were collected at the baseline and during the 72 h post-dose, and plasma empagliflozin concentrations were determined by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). Pharmacokinetic parameters were analyzed with non-compartmental methods. Safety was monitored. The major PK parameters including Cmax, AUC0–t, and AUC0-∞ were similar between the generic and brand-named tablets under fasting and fed conditions (all p >.05). The 90% confidence intervals of the test/reference ratios of log-transformed Cmax, AUC0–t, and AUC0-∞ were 94.90–106.70%, 100.62–106.99%, and 100.64–106.85%, respectively, under fasting condition, and 94.21–104.91%, 97.31–101.79%, and 97.32–101.83%, respectively, under fed condition. High-fat food did not affect Cmax, AUC0–t, AUC0–∞, or Tmax of empagliflozin (all p >.05). There was no serious adverse event during the study period. The generic formulation of empagliflozin tablet is bioequivalent to the brand-named product in healthy Chinese volunteers, and well tolerated. High-fat food had no effects on the PK of empagliflozin in healthy Chinese volunteers. [ABSTRACT FROM AUTHOR]

The effect of different doses of borneol on the pharmacokinetics of vinpocetine after intraocular administration in the rat plasma and the brain was investigated. Intraocular administration of vinpocetine (3 mg/kg) was performed, in combination with different doses (0, 5, 10, and 20 mg/kg) of borneol. Intravenous administration of vinpocetine was used as a control (1 mg/kg). The concentrations of vinpocetine in the rat plasma and the brain were determined using a liquid chromatography-tandem mass spectrometry (LC–MS/MS) method. Using the non-compartmental models with the DSA 2.0 software, the main pharmacokinetics parameters and the brain-targeting effect evaluated. In comparison with intravenous administration, after intraocular administration of vinpocetine alone, the absolute bioavailability (F) of vinpocetine was 43.82% for the plasma, and the drug target index (DTI) was 1.05 for the brain. After intraocular administration of vinpocetine combined with different doses of borneol, the relative bioavailability (Fr) of vinpocetine in the plasma was increased by 130.46–182.90%. The relative bioavailability (Fr) of vinpocetine in the brain was improved (147.19–225.36%). The DTI was 1.12, 1.18, and 1.21 for 5, 10, and 20 mg/kg of borneol, respectively. Compared with the intraocular administration of vinpocetine alone, the co-administration of different doses of borneol resulted in an obvious brain targeting effect. [ABSTRACT FROM AUTHOR]

Cenobamate is a candidate drug that is being evaluated in a phase 3 clinical trial as an epilepsy treatment. In the present study, we developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for assaying cenobamate in rat plasma. Acetonitrile was used for plasma protein precipitation, whereas carisbamate was used as the internal standard. A Spursil C18 column and 10 mM ammonium formate and acetonitrile (60:40, v/v) were used for chromatographic separation. Detection was done using a triple quadrupole mass spectrometer by multiple reaction monitoring at transitions of m/z 268.06 ➜ 198.00 for cenobamate and m/z 216.09 ➜ 198.10 for carisbamate. The standard curve (r = 0.9946) was linear over a concentration range of 10 – 5000 ng/mL. Intra- and inter-day precision values were <14.97 and 14.86%, respectively, whereas intra- and inter-day accuracy values were less than 3.37 and 7.13%, respectively. Matrix effect, extraction recovery, and process efficiency were 98.59, 93.97, and 92.58%, respectively. Furthermore, cenobamate remained stable in rat plasma samples following three freeze-thaw cycles, storage at room temperature for 6 h, long-term storage at −20 °C for 4 weeks. The LC-MS/MS method was successfully used for studying the pharmacokinetics of cenobamate in rats. [ABSTRACT FROM AUTHOR]

An LC-MS/MS method for analysis of daptomycin in dried blood spot (DBS) was established. The DBS samples were prepared by spotting one droplet of blood onto absorbent paper, and were left to dry at room temperature. The DBS samples were extracted with water followed by deproteinization with acetonitrile. A Hypersil GOLD aQ column was applied to chromatographically separate the analyte, and mobile phase at a flow rate of 0.3 mL/min consisted of methanol and 0.1% formic acid. Detection of analyte was performed on a triple quadrupole mass spectrometer in positive mode, and the mass spectrometer was manipulated in selective reaction monitoring (SRM) mode. The SRM transitions m/z 810.9→811.1 and 810.9→640.8 for quantification and qualification of daptomycin and m/z 837.4→679.4 and 837.4→558.3 for roxithromycin used as internal standard were monitored. The calibration curves covering the range of 1-200 μg/mL exhibited good linearity, and lower limit of quantification (LLOQ) was 1 µg/mL for daptomycin in DBS. The proposed method was fully validated, and hematocrit effect on the quantification of daptomycin in DBS was not obvious. The proposed DBS method was non-invasive and required collection of a micro-volume blood, and was successfully utilized to a pharmacokinetics study in seriously ill patients. [ABSTRACT FROM AUTHOR]

The objective of this work was to develop a simple, selective, and sensitive LC–MS/MS method for the quantitation of the mepivacaine in Chinese biological matrix. The calibration curve of mepivacaine ranged from 0.5 to 2000 ng/mL with the lower limit of quantitation being 0.5 ng/mL. This sensitivity was high enough to describe the profile of blood mepivacaine level versus time. Thereby it was very desirable for the pharmacokinetic study because of its high sensitivity and accuracy. The study used a single-dose two-period crossover design principle. For the pharmacokinetic analysis of plasma, the mean (SD) values obtained were as follows: t1/2, 1.63 (0.43) h;Cmax, 435.3 (67.4) ng/ml;AUC0-t, 1546.9 (339.7) ng/ml·h;AUC0-∞, 1982.3 (421.4) ng/ml·h;Tmax, 0.62 (0.31) h. The validated method has been successfully applied to assess the pharmacokinetic study of mepivacaine after a single administration to Chinese volunteers. [ABSTRACT FROM PUBLISHER]

The objective of this study was to compare two lansoprazole products (the reference brand enteric-coated capsules and the test generic enteric-coated tablets), and the key pharmacokinetic (PK) parameters for both formulations and their metabolites were assessed. The study used an open-label, randomized two-period crossover design with an 8-day washout period between doses in 24 healthy subjects under fasting conditions. The concentration of lansoprazole and its two metabolites was determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Thein vitrorelease of lansoprazole from the test and reference formulations was within the acceptable limits. The relationship between concentration and peak area ratio was found to be linear within the range for lansoprazole and metabolites. The point estimates (ratios of geometric mean) of lansoprazole and two main metabolites were between 94.3% and 105.1% for AUC0−t, AUC0−∞, andCmax. No statistically significant difference between the two formulations was found. The results ofin vitroandin vivosuggested equivalent clinical efficacy of the two brands. [ABSTRACT FROM AUTHOR]

1. In this study, the stereoselective pharmacokinetics of rhynchophylline (RIN) and isorhynchophylline (IRN) in rat plasma were investigated using liquid chromatography–tandem mass spectrometry (LC–MS/MS). 2. A rapid, robust and sensitive LC–MS/MS method for simultaneous quantification of RIN and IRN in rat plasma was established and validated. Chromatographic separation was performed on a Poroshell 120 EC-C18column under a gradient elution with methanol and water containing 0.01% ammonia as mobile phase. Calibration curve was linear over a concentration range of 1–2000 ng/mL for both epimers. 3. After intravenous administration, there was no apparent difference in pharmacokinetic parameters between two epimers. However, after oral administration, RIN showed remarkable higher plasma exposure than IRN. The bioavailability,Cmaxand AUC0–tof RIN were about 9.2-fold, 6.4-fold and 9.1-fold higher than those of IRN at 10 mg/kg, and 7.8-fold, 4.3-fold and 7.7-fold at 20 mg/kg, respectively. Additionally, with dosage enhanced from 10 mg/kg to 20 mg/kg, the plasma concentrations of RIN or IRN increased significantly and the bioavailability enhanced about three times. 4. In conclusion, the results of this work demonstrated for the first time that the pharmacokinetics of RIN and IRN have stereoselectivity. [ABSTRACT FROM PUBLISHER]

A rapid and robust method for measuring methotrexate (MTX) and its two primary metabolites, 7-hydroxymethotrexate (7-OHMTX) and 2,4-diamino-N10-methylpteroic acid (DAMPA), was developed for use in pharmacokinetic studies of plasma and cerebrospinal fluid samples collected from infants with malignant brain tumors. Sample aliquots (100 µL) were prepared for bioanalysis of MTX and metabolites using a Waters Oasis HLB microelution solid-phase extraction (SPE) plate. Chromatography was performed using a Phenomenex Synergi Polar-RP 4 µ 75 × 2.0 mm ID column heated to 40°C. A rapid gradient elution on a Shimadzu HPLC system was used, with mobile phase A consisting of water/formic acid (100/0.1 v/v) and mobile phase B consisting of acetonitrile/formic acid (100/0.1 v/v). Column eluent was analyzed using AB Sciex QTRAP 5500 instrumentation in electrospray ionization mode. The ion transitions (m/z) monitored were 455.2 → 308.1, 471.1 → 324.1, and 326.2 → 175.1 for MTX, 7-OHMTX, and DAMPA, respectively. The method was linear over 0.0022–5.5 µM for MTX, 0.0085–21 µM for 7-OHMTX, and 0.0031–7.7 µM for DAMPA. The method was applied to the analysis of serial plasma samples obtained from infants diagnosed with malignant brain tumors receiving high-dose methotrexate and results were compared to MTX concentrations from an immunoassay based on fluorescence polarization. [ABSTRACT FROM AUTHOR]

Synthetic cannabinoids (SC), originally developed as research tools, are now highly abused novel psychoactive substances. We present a comprehensive systematic review covering in vivo and in vitro animal and human pharmacokinetics and analytical methods for identifying SC and their metabolites in biological matrices. Of two main phases of SC research, the first investigated therapeutic applications, and the second abuse-related issues. Administration studies showed high lipophilicity and distribution into brain and fat tissue. Metabolite profiling studies, mostly with human liver microsomes and human hepatocytes, structurally elucidated metabolites and identified suitable SC markers. In general, SC underwent hydroxylation at various molecular sites, defluorination of fluorinated analogs and phase II metabolites were almost exclusively glucuronides. Analytical methods are critical for documenting intake, with different strategies applied to adequately address the continuous emergence of new compounds. Immunoassays have different cross-reactivities for different SC classes, but cannot keep pace with changing analyte targets. Gas chromatography and liquid chromatography mass spectrometry assays - first for a few, then numerous analytes - are available but constrained by reference standard availability, and must be continuously updated and revalidated. In blood and oral fluid, parent compounds are frequently present, albeit in low concentrations; for urinary detection, metabolites must be identified and interpretation is complex due to shared metabolic pathways. A new approach is non-targeted HRMS screening that is more flexible and permits retrospective data analysis. We suggest that streamlined assessment of new SC's pharmacokinetics and advanced HRMS screening provide a promising strategy to maintain relevant assays. [ABSTRACT FROM AUTHOR]

Metabolites of omega-3 fatty acids can inhibit primary tumor growth, angiogenesis, and tumor metastasis. Effective treatment for brain tumors is an unmet need as many chemotherapies are unable to cross the blood–brain barrier efficiently. As fatty acids are capable of entering the brain, these agents may have potential for treating brain tumors. In this communication a reliable and sensitive LC-MS/MS method was developed and validated for quantitation of ethyl 16-{[(4-methylphenyl)carbamoyl]amino}hexadecanoate (CUT-EE), a urea-based analog of eicosapentaenoic acid. The assay has acceptable intra- and inter-assay accuracy and precision over the range 0.25–125 ng/mL, and a lower limit of quantitation of 0.25 ng/mL. Non-aqueous, mouse brain, and plasma solutions of CUT-EE were stable during short-term and long-term storage, and after three freeze-thaw cycles. This method was applied to determine concentrations of CUT-EE in brain and plasma following administration to mice at 50 mg/kg. CUT-EE was cleared from the plasma within 24 hr, whilst concentrations in the brain increased over 24 hr and remained stable out to 48 hr. The calculated area under the concentration curve in brain was over 100 times greater than that found in plasma, supporting further investigations of CUT-EE for its potential in treating brain cancers. [ABSTRACT FROM AUTHOR]

A novel liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the determination of rosuvastatin (rosuva) and its metabolite N-desmethyl rosuvastatin (NDM-rosuva) in human plasma using atorvastatin as internal standard. The method was validated according to international guidelines. The analytical column used was HiChrom®C18 (150 × 3.0 mm, 3 µm; Reading, UK) and the mobile phase comprised of 0.1% formic acid in acetonitrile and 0.1% formic acid in water (70:30 v/v), pumped at 300 µL/min. The precipitation of plasma proteins and extraction of analytes were carried out by a simple one-step procedure using acetonitrile. The calibration curves were linear (r2 = 0.999) over the concentration range of 0.2–20 ng/mL for rosuva and 0.1–10 ng/mL for NDM-rosuva. The lower limits of detection and quantification for rosuva were 0.1 and 0.2 ng/mL, whereas for NDM-rosuva, these were 0.03 and 0.1 ng/mL, respectively. The intra- and inter-day precisions expressed as relative standard deviations (RSDs) were less than 2.5%. The average absolute recoveries of both rosuva and NDM-rosuva were greater than 95%. The method was successfully applied for the determination of rosuva and NDM-rosuva pharmacokinetics and drug–drug interaction studies. [ABSTRACT FROM AUTHOR]

This is the first publication on a complete validated bioanalytical method for estimation of olmesartan (OLM) and hydrochlorothiazide (HCTZ) in human K3 EDTA plasma that chromatographically resolves its olmesartan glucuronide. An API 4000 mass spectrometer was employed in this method where olmesartan d4 (OLMD4) and hydrochlorothiazide −13C, d2 (HCTZD2) served as the internal standard. Sample was prepared by solid phase extraction (SPE) technique using a polymer based, MCX cartridges and chromatographic resolution achieved on Synergi MAX RP-18A, (4.6 × 150 mm, 4 μm) column using a mobile phase of 0.2% formic acid solution/acetonitrile (30:70, v/v). Negative mass transitions (m/z) of OLM, HCTZ, OLMD4, and HCTZD2 were detected in multiple reactions monitoring (MRM) mode at 445.5 → 149.3, 296.0 → 269.0, 449.2 → 149.3, and 299.1→270.0, respectively. The linearity was checked over a concentration range of 4.051-2500.912 ng/mL for OLM and 0.506-304.109 ng/mL for HCTZ. Intra- and inter-run precision of OLM and HCTZ assay at four concentration levels were below 3.7% and 4.3%, and accuracy was within ±4.4% and 3.0%, respectively. Mean recoveries for OLM, HCTZ, and internal standards OLMD4 and HCTZD2 were 75.68, 77.60%, and 80.2, 89.1%, respectively. This method has been successfully applied to pharmacokinetic biostudy. [ABSTRACT FROM AUTHOR]

A selective, sensitive, liquid chromatography–positive electrospray ionization tandem mass spectrometry method was developed and validated for the simultaneous quantification of fluoxetine and olanzapine in human plasma using duloxetine (IS) as an internal standard. The analytes and IS were extracted from a 0.250-mL aliquot of human plasma by liquid–liquid extraction using methyl tertiary butyl ether and n-hexane (80:20). The eluted samples were chromatographed with a run time of 3.20 min on X-terra RP8 4.6 × 50 mm, 5 µm column by using a 90:10v/vmixture of acetonitrile and 5 mM ammonium acetate buffer (PH5.00 ± 0.05) as an isocratic mobile phase at a flow rate of 0.4 mL/min, and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M+H]+ions,m/z310.16 → 114.12 for fluoxetine, 313.19 → 256.12 for olanzapine, and 298.14→154.09 for the IS, respectively. Calibration plots were linear over the concentration range of 0.050 to 25.044 ng/mL for fluoxetine and 0.100 to 50.000 ng/mL for olanzapine. Intra-day and inter-day precision and accuracy for quality control samples of fluoxetine (0.150, 12.832, and 19.433 ng/mL) ranged between 2.95 to 10.02% and between 97.90 to 103.25% and for olanzapine (0.300, 25.000, and 38.515 ng/mL) ranged between 3.30 to 7.66% and between 100.75 to 103.11%, respectively. Matrix effect, recovery, and process efficiency experiment was conducted at five different standards, the absolute extraction efficiency was 83.32% for fluoxetine, 86.30% for olanzapine, and 77.73% for IS. This method was successfully applied on pharmacokinetic study. [ABSTRACT FROM AUTHOR]

To investigate the pharmacokinetics of letrozole in healthy postmenopausal Chinese women, a rapid, selective, and sensitive liquid chromatography–tandem mass spectrometric method in negative ionization mode was developed and validated to determine letrozole in human plasma using d4-letrozole as the internal standard (IS). Following protein precipitation, effective chromatographic separation was accomplished on a Capcell PAK C18MG column (100 mm × 4.6 mm, 5 µm) with a mobile phase consisting of methanol–10 mM ammonium acetate (65:35, v/v) at a flow rate of 0.6 mL/min. The running time was 4.0 min. The detection of the analyte and IS was carried out in selective reaction monitoring mode via negative electrospray ionization interface. The method was linear over concentrations ranging from 0.40 ng/mL to 50.0 ng/mL. The lower limit of quantification was 0.40 ng/mL, which allowed the measurement of letrozole concentration up to 240 hr after oral administration. The intraday and interday precisions were less than 12.9% in terms of the relative standard deviation, and the accuracy was within ±7.4% in terms of the relative error. Finally, this validated method was successfully applied to the clinical pharmacokinetic study after a single oral administration of 2.5 mg letrozole to 20 healthy, postmenopausal Chinese women. [ABSTRACT FROM PUBLISHER]

A highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of venlafaxine (VEN) and its active metabolite O-desmethyl venlafaxine (ODV) in human plasma using fluoxetine as an internal standard. The VEN and ODV were extracted by liquid–liquid extraction using MTBE-n Hexane (60:40), and chromatographed on X-terra RP8 (50 mm × 4.6 mm, 5-µm particle size) column eluted with a isocratic mobile phase of 10 mM Ammonium acetate (pH 4.50 ± 0.05) and acetonitrile in 10:90 (v/v). The detection was performed by positive ion electrospray ionization in multiple reactions monitoring mode, monitoring the transitions m/z 278.27→ 121.08 and 264.33 → 57.72 for venlafaxine and O-desmethyl venlafaxine, respectively. The assay was linear over the concentration ranges of 0.100–300.010 ng/mL for VEN and 0.200–600.050 ng/mL for ODV with limits of detection and quantification of 0.050 ng/mL for VEN and 0.100 ng/mL for ODV, respectively. This LC-MS/MS method was validated with Intra-batch and Inter-batch precision 1.65–10.80 for VEN and 1.27–7.08 for ODV, respectively. The Intra-batch and Inter-batch %accuracy was 91.77%–104.39% for VEN and 95.87%–106.28% for ODV, respectively. This method was successfully applied to a pharmacokinetic study of venlafaxine hydrochloride extended release capsules 150 mg steady-state bioequivalence study. [ABSTRACT FROM PUBLISHER]

A highly selective and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of scicinib, a novel thiosemicarbazone analogue and anticancer agent in rat plasma. Protein precipitation with saturated EDTA solution and methanol was selected for sample preparation, and brodimoprim was employed as the internal standard (IS). The analytes were separated on a Symmetry C18column (200 × 4.6 mm i.d., 5 µm) by isocratic elution with a mobile phase consisting of methanol and 0.2 mM EDTA (75:25, v/v) at a flow rate of 0.4 mL/min. After electrospray ionization, the analyte and IS were recorded under selected reaction monitoring (SRM) mode. The chosen transition wasm/z313.0 → 267.9 for scicinib andm/z339.0 → 280.9 for IS, respectively. The validated linearity range is 5–5000 ng/mL, with the lower limit of quantitation of 5 ng/mL. The developed method was successfully applied to a pharmacokinetic study of scicinib in rats after a single intravenous administration of 5 mg/kg. [ABSTRACT FROM AUTHOR]

A highly sensitive, rapid assay method has been developed and validated for the quantification of clozapine in rat plasma using LC-MS/MS. The extraction process involved plasma protein precipitation with acetonitrile and elution with a mobile phase constituted by acetonitrile and acidic water (80/20), at 0.8 mL/min flow rate (split 1:3). Chromatographic separation was performed by C18 Symmetry column (4.6 × 75 mm, 3.5 µm). The lower limit of quantification was 1 ng/mL and the linearity was observed between 1–1000 ng/mL with a determination coefficient >0.9810. The intra- and inter-day precisions were less or equal to 8.38 and 4.36%, respectively. The method showed sensitivity, linearity, precision, accuracy, and specificity necessary for quantification of plasma clozapine in preclinical pharmacokinetics studies. [ABSTRACT FROM PUBLISHER]

A simple, sensitive, and rapid liquid chromatography-tandem mass spectrometry method for determination of memantine in human plasma was established. A one-step protein precipitation with methanol was used to extract the analyte from plasma samples. Memantine and amantadine (internal standard, IS) were separated on a YMC-ODS-C18 column using 0.1% formic acid and methanol as a mobile phase at a flow rate of 0.3 mL/min. Detection was performed on positive ion mode of the transitions at 180.3→107.3 for memantine and 152.2→135.3 for IS by selected reaction monitoring (SRM). The assay was validated over the concentration range of 0.5–50 ng/mL with a lower limit of quantification (LLOQ) of 0.5 ng/mL. The intra- and inter-batch precision (RSD) were no more than 5.96% and 6.37%, respectively. The accuracy was from −3.02% to 7.74%. The validated method was successfully applied to a randomized, 2-period cross-over bioequivalence study in 22 healthy Chinese volunteers following a single oral dose of 10 mg memantine hydrochloride tablet. The simple, inexpensive protein precipitation and high-throughput method makes it a suitable and valuable tool in the investigation of the clinical pharmacokinetics and bioequivalence. [ABSTRACT FROM PUBLISHER]

A simple and rapid liquid chromatography-tandem mass spectrometry (LC–MS/MS) method has been developed and validated for the quantitation of indirubin-5-nitro-3′-monoxime (5-NIO) in rat plasma using 5-chloro-5′-chloro-indirubinoxime as the internal standard. The sample preparation involved protein precipitation using acetonitrile. Separation was achieved on an Xterra column C18 (2.1 mm × 50 mm, i.d. 5 µm) using a mixture of 0.1% formic acid-water/acetonitrile (18:82, v/v) as the mobile phase at a flow rate of 300 µL/min. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization and multiple reaction monitoring (MRM) in negative ion mode. The total chromatographic run time was 2.5 min, and the calibration curves of 5-NIO were linear (correlation coefficient range: 0.9989–0.9999) over the concentration range of 0.2–2000 ng/mL in rat plasma. Also, the detection limit of the method was 0.05 ng/mL and it showed good accuracy and precision within the concentration range of 0.45–376 ng/mL. This validated method was successfully applied to estimating the pharmacokinetic parameters of 5-NIO following intravenous administration of 5-NIO to rats. [ABSTRACT FROM AUTHOR]

A simple and specific LC-MS/MS method for the determination of FK506 in blood was developed, validated, and successfully applied in pharmacokinetic studies of the effect of silymarin on FK506 in rats. Blood samples were extracted by liquid-liguid extraction with methyl tert-butyl ether and separated on an Eclipse plus-C18 column (150 × 2.1 mm, 3.5 µm) with the mobile phase of acetonitrile-10 mM ammonium acetate buffer solution (80:20, v/v). FK506 was detected without interference in the multiple-reaction monitoring mode with positive electrospray ionization. Good linearity was achieved over a range of 2.0–200 ng mL−1. The intra- and inter-day precisions were less than 13.5 % for all concentrations of quality control samples. The recoveries of FK506 were 74.2–85.3 %. Although the mean Cmax and AUC0 − ∞ of FK506 were increased to some extent, there was no significant difference in the pharmacokinetic profile of FK506 after oral administration to rats in the presence and absence of silymarin (200 mg kg−1, 2 times/d for 14 d). [ABSTRACT FROM AUTHOR]

The tissue distribution and residue depletion of carbadox and its metabolites (QCA) were investigated in swine after a single oral dose of 3.5 mg/kg of body weight of carbadox and multiple dose (2 weeks) in-feed (50 ppm) administration. Plasma, muscle, liver, and kidney were sampled pre- and post-treatment and, subsequently, analyzed for carbadox and QCA concentrations using liquid chromatography with tandem mass spectrometry (LC-MS-MS). Carbadox concentration in plasma peaked 2 hr after a single oral dose administration, while QCA concentration was still detectable in liver tissue (2 ng/g) at the fifth week and in kidney tissue (0.9 ng/g) at the sixth week after withdrawal. The volume of distribution (V) of carbadox is 4700 + /−2200 mL/kg and areas under the concentration curves (2.36 + /−0.86 hr µg/mL) indicated that the drug was adequately distributed throughout the body from the blood of pigs. The slow elimination of the carbadox metabolites suggests a need for long withdrawal periods prior to the use of dosed swine for human consumption. [ABSTRACT FROM PUBLISHER]