Quantification of leonurine, a novel potential cardiovascular agent, in rat plasma by liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic study in rats

Leonurine (SCM‐198), an alkaloid from Herba Leonuri, has been suggested as a novel cardiovascular agent by pharmacology studies in preclinical stage. In present study, we report a simple, rapid and sensitive high‐performance liquid chromatography–tandem mass spectrometry method (HPLC‐MS/MS) for determination of leonurine in rat plasma. Leonurine and its internal standard (IS) n‐benzoyl‐l ‐arginine ethyl ester (BAEE) were extracted from plasma samples by one‐step protein precipitation with perchloric acid. Chromatographic separation was performed on an Agilent Zorbax SB‐C₁₈ column (150 × 2.1 mm, 5 µm) using an isocratic elution with acetonitrile–ammonium acetate buffer (10 mm , pH 4.0; 25:75, v/v) as mobile phase at a flow rate of 0.2 mL/min. Analytes were detected by tandem mass spectrometry in positive electrospray ionization (ESI) mode using multiple reaction monitoring (MRM) with the transitions of m/z 312.3 → 181.1 for leonurine and m/z 307.2 → 104.6 for IS. The calibration curves were linear over the range of 4–256 ng/mL with a lower limit of quantitation (LLOQ) of 4 ng/mL. The intra‐ and inter‐day assay precision (as relative standard deviation) were <15%, except which at LLOQ were <20%, with accuracy in the range 98.73‐105.42%. The validated HPLC‐MS/MS method was successfully applied to the pharmacokinetic study in rats following oral administration of leonurine. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of ecliptasaponin A in rat plasma and tissues by liquid chromatography‐tandem mass spectrometry

A sensitive, rapid and specific high‐performance liquid chromatography tandem mass spectrometry method (HPLC‐MS/MS) was developed to determine ecliptasaponin A in rat plasma and tissues after oral administration. Ginsenoside Rg1 was used as the internal standard (IS). The plasma and tissues samples were prepared by liquid‐liquid extraction with ethyl acetate and separated on an Eclipse Plus C₁₈ column (2.1 mm × 150 mm, 5 µm) at a flow rate of 0.4 mL/min using acetonitrile and water (containing 0.05% acetic acid) as the mobile phase. The tandem mass detection was carried out with eletrospray ionization in negative mode. Quantification was performed by using multiple reaction monitoring (MRM), which monitored the fragmentation of m/z 633.4→587.2 for ecliptasaponin A and m/z 859.4→637.4 for the IS. The calibration curves obtained were linear in different matrices, and the lower limit of quantification (LLOQ) achieved was 0.5 ng/mL both for rat plasma and tissues. The intra‐ and inter‐day precisions were below 15%. This method was successfully applied to pharmacokinetic study of ecliptasaponin A in rat plasma and tissues after oral administration. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of tubuloside B by LC‐MS/MS and its application to a pharmacokinetic study in rats

Tubuloside B, a novel neuroprotective phenylethanoid, is a major active constituent of Cistanche tubulosa and Cistanche deserticola. A specific and sensitive liquid chromatography tandem mass spectrometry (LC‐MS/MS) method has been developed and validated for the quantification of tubuloside B in rat plasma. Sample preparation was conducted through a protein‐precipitation extraction with methanol using tubuloside A as internal standard (IS). Chromatographic separation was achieved using a Capcell Pak C₁₈ column (2.0 × 50 mm, 5 μm) with a mobile phase of methanol–10 mm ammonium acetate buffer (70:30, v/v) in an isocratic elution. Mass spectrometry analysis was performed in negative ionization mode with selected reaction monitoring transitions at m/z 665.1 → 160.9 for tubuloside B, and m/z 827.1 → 160.9 for IS. Calibration curves were linear over the range of 1.64–1640 ng/mL for plasma samples samples (R² > 0.990). The lower limit of quantification (LLOQ) was 1.64 ng/mL. The intra‐ and inter‐day accuracy was between 92.3 and 113.0% with the RSD <9.23% at all LLOQ and quality control levels. Finally, this method was successfully applied in the pharmacokinetics study of tubuloside B after intravenous administration.     

Validated UPLC‐MS/MS method for determination of moclobemide in human brain cell supernatant and its application to bidirectional transport study

A simple and sensitive analytical method based on ultraperformance liquid chromatography–tandem mass spectrometry (UPLC‐MS/MS) has been developed for determination of moclobemide in human brain cell monolayer as an in vitro model of blood–brain barrier. Brucine was employed as the internal standard. Moclobemide and internal standard were extracted from cell supernatant by ethyl acetate after alkalinizing with sodium hydroxide. The UPLC separation was performed on an Acquity UPLC^TM BEH C₁₈ column (50 × 2.1 mm, 1.7 µm, Waters, USA) with a mobile phase consisting of methanol–water (29.5:70.5, v/v); the water in the mobile phase contained 0.05% ammonium acetate and 0.1% formic acid. Detection of the analytes was achieved using positive ion electrospray via multiple reaction monitoring mode. The mass transitions were m/z 269.16 → 182.01 for moclobemide and m/z 395.24 → 324.15 for brucine. The extraction recovery was 83.0–83.4% and the lower limit of quantitation (LLOQ) was 1.0 ng/mL for moclobemide. The method was validated from LLOQ to 1980 ng/mL with a coefficient of determination greater than 0.999. Intra‐ and inter‐day accuracies of the method at three concentrations ranged from 89.1 to 100.9% for moclobemide with precision of 1.1–9.6%. This validated method was successfully applied to bidirectional transport study of moclobemide blood–brain barrier permeability. Copyright © 2013 John Wiley & Sons, Ltd.     

New UPLC–MS/MS method for simultaneous determination of irbesartan and hydrochlorthiazide in human plasma

Ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) is a preeminent analytical tool for rapid biomedical analysis with the objective of reducing analysis time and maintaining good efficiency. In this study a simple, rapid, sensitive and specific ultra-performance liquid chromatography–tandem mass spectrometry method was developed and validated for quantification of the angiotensin II receptor antagonist, irbesartan and hydrochlorthiazide in human plasma. After a simple protein precipitation using methanol and acetonitrile, irbesartan, hydrochlorthiazide and internal standard (IS) telmisartan were separated on Acquity UPLC BEH? C18 column (50 × 2.1 mm, i.d. 1.7 μm, Waters, USA) using a mobile phase consisting of acetonitrile:10 mM ammonium acetate:formic acid (85:15:0.1 % v/v/v) pumped at a flow rate of 0.3 mL/min and detected by tandem mass spectrometry with negative ion mode. The ion transitions recorded in multiple reaction monitoring mode were m/z 427.2 → 193.08 for irbesartan, m/z 295.93 → 268.90 for hydrochlorthiazide and m/z 513.2 → 287.14 for IS. The assay exhibited a linear dynamic range of 30–500 ng/mL for irbesartan and 1–500 ng/mL in human plasma with good correlation coefficient of (0.996) and (0.997) and with a limit of quantitation of 30  and 1 ng/mL for irbesartan and hydrochlorthiazide, respectively. The intra- and inter-assay precisions were satisfactory; the relative standard deviations did not exceed 10.13 % for irbesartan and 11.14 % for hydrochlorthiazide. The proposed UPLC–MS/MS method is simple, rapid and highly sensitive, and hence it could be reliable for pharmacokinetic and toxicokinetic study in both animals and humans.     

A high selective and sensitive liquid chromatography–tandem mass spectrometry method for quantization of BPA urinary levels in children

A selective and highly sensitive liquid chromatography–tandem mass spectrometry method has been developed and validated for determination of Bisphenol A (BPA) in human urine using labeled d₆-BPA as internal standard. BPA was purified from human urine by affinity chromatography on solid extraction AFFINIMIP® Bisphenol A cartridges, based on molecularly imprinted polymers. After purification, the samples were analyzed on a Phenomenex Kinetex 100?×?4.6 mm, 2.6 μm particle PFP reversed-phase HPLC column, coupled to a triple quadrupole mass spectrometer by an electrospray ion source. Analyses were performed in the multiple reaction monitoring mode and negative ionization; the product ions at 133.2 and 212.1?m/z for BPA and at 138.2 and 215.0?m/z for d₆-BPA were monitored to assess unambiguous identification. The linearity of the detector response was verified in human urine over the concentration range 0.100–200 ng/mL. The detection limit was calculated as 0.03 ng/mL and the limit of quantification of the method is 0.10 ng/mL. This LC/ESI-MS/MS method was in-house validated evaluating specificity, trueness, within-day and between-days precision. The mean recoveries of BPA from spiked urine samples were higher than 94 % and good reproducibility (relative standard deviations?≤?8.1 %) was observed. The developed method was applied to a pilot study involving 105 children, aged from 6 to 14 years (16 normal weight and 89 obese children), from the Regione Campania (Southern Italy). The aim of this study was to determine the concentrations of BPA in urine of children and possible correlations with childhood obesity.     

LC–MS–MS Determination of Troxerutin in Plasma and Its Application to a Pharmacokinetic Study

A highly sensitive liquid chromatography–tandem mass spectrometry (LC–MS–MS) method for the determination of troxerutin in human plasma using tramadol as internal standard (IS) has been developed and validated. Sample preparation involved liquid–liquid extraction with ethyl acetate–isopropanol (95:5, v/v). The analyte and IS were separated by RP–LC with gradient elution using 10 mM ammonium acetate containing 0.1% formic acid and methanol at a flow rate of 0.9 mL min^?1. LC–MS–MS in the positive ion mode employed multiple reaction monitoring of the transitions at m/z 743.2→435.3 and m/z 264.1→58.0 for troxerutin and IS, respectively. The assay was linear in the concentration range 0.01–10 ng mL^?1 with precision and accuracy within assay variability limits as per FDA guidelines. The assay was successfully applied to a pharmacokinetic study involving oral administration of 300 mg troxerutin to eight healthy Chinese volunteers.     

LC-MS-MS Determination and Pharmacokinetic Study of Clozapine in Human Plasma

A sensitive and selective liquid chromatographic method coupled with tandem mass spectrometry was established and validated for the determination and pharmacokinetic study of clozapine in human plasma. Ethyl acetate extraction was used for plasma sample preparation with mirtazapine as internal standard. Chromatographic separation was achieved on a Hanbon Kromasil C₁₈ (250 mm × 4.6 mm, 5 μm) column by isocratic elution with a mixture of 70 volumes of methanol and 30 volumes of water containing 0.2% ammonium acetate and 0.1% formic acid as mobile phase delivered at 1.0 mL min^?1. The MS-MS detection was carried out on a tandem mass spectrometer using positive electrospray ionization and multiple reaction monitoring with argon for collision-induced dissociation. The ion transitions were monitored as follows: m/z 327 to m/z 270 for clozapine and m/z 266 to m/z 195 for the internal standard (mirtazapine), respectively. Calibration curves were generated over the concentration range from 0.10 to 200 ng mL^?1 with the lower limit of quantification of 0.10 ng mL^?1, and two segments of linear calibration curves were established by regressing in the way of least-square in the range from 0.10 to 5.0 and 5.0 to 200 ng mL^?1, respectively. The intra- and inter-day precision and accuracy were determined at three different concentration levels, 0.20, 10.0 and 100 ng mL^?1, and were all better than 15% (n = 5). This specific and sensitive liquid chromatography coupled with tandem mass spectrometry has been successfully applied to a pharmacokinetic study of clozapine after a single oral dose of 25 mg in healthy Chinese volunteers.     

A Sensitive LC–ESI–MS–MS Method for the Determination of Huperzine A in Human Plasma: Method and Clinical Applications

A sensitive and specific liquid chromatography–electrospray ionization–tandem mass spectrometry method has been developed and validated for the quantification of huperzine A in human plasma. After the addition of trimetazidine, the internal standard (IS) and sodium hydroxide, plasma samples were extracted using 5 mL ethyl acetate. The compounds were separated on an Agilent Zorbax SB C₁₈ column (100 mm × 2.1 mm ID, dp 3.5 μm) using an elution system of 10 mM ammonium acetate solution–methanol–formic acid (18:82:0.1, v/v) as the mobile phase. The quantification of target compounds was obtained by using multiple reaction monitoring (MRM) transitions: m/z 243.1, 210.1 and 267.2, 166.0 were measured in positive mode for huperzine A and IS. Linearity was established for the range of concentrations 0.01–4.0 ng mL^?1 with a coefficient of correlation (r) of 0.9991. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.01 ng mL^?1. The method has been successfully applied to study the pharmacokinetics of huperzine A in healthy male Chinese volunteers.     

Analysis and Confirmation of Rodenticide Pindone in Human Plasma by IC–ESI–IT–MS

Pindone is a highly effective anticoagulant rodenticide. In this paper, an improved assay for the analysis and confirmation of pindone in human plasma has been proposed. After the samples protein precipitation with 10% (v/v) methanol in acetonitrile and cleaning with solid-phase extraction, the separation was carried out on an IonPac AS11-HC analytical column (250 mm × 2 mm) using 20 mmol L^?1 KOH containing 10% (v/v) methanol as organic modifier by eluent generator reagent free ion chromatography. Quantification was performed by a negative electrospray ionization ion trap mass spectrometry using diphacinone as an internal standard. The transition for quantitative analysis was m/z 229 → 172, and for qualitative analysis were m/z 229 → 145 and m/z 229 → 214 for pindone. The transition for quantitative analysis was m/z 339 → 167 for IS. The limit of detection, the limit of quantification, recovery, linearity, precision, and stability were well validated. The cracking approach of characteristic fragments for pindone and IS were proposed. It was confirmed that this method could be used in clinical diagnosis and forensic toxicology analysis.     

Determination of limonin in dog plasma by liquid chromatography–tandem mass spectrometry and its application to a pharmacokinetic study

A highly sensitive liquid chromatography–tandem mass spectrometry method was developed and validated for the determination of limonin in beagle dog plasma using nimodipine as internal standard. The analyte and internal standard (IS) were extracted with ether followed by a rapid isocratic elution with 10 mm ammonium acetate buffer–methanol (26:74, v/v) on a C₁₈ column (150 × 2.1 mm i.d.) and subsequent analysis by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 469.4 → 229.3 and m/z 417.2 → 122.0 were used to measure the analyte and the IS. The assay was linear over the concentration range of 0.625–100 ng/mL for limonin in dog plasma. The lower limit of quantification was 0.312 ng/mL and the extraction recovery was >90.4% for limonin. The inter‐ and intra‐day precision of the method at three concentrations was less than 9.9%. The method was successfully applied to pharmacokinetic study of limonin in dogs. Copyright © 2012 John Wiley & Sons, Ltd.     

Simultaneous determination of tofacitinib and its principal metabolite in beagle dog plasma by UPLC-MS/MS and its application in pharmacokinetics

The main objective of our current study is to develop and validate an accurate and direct ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method to simultaneously detect plasma concentrations of tofacitinib and its metabolite M9, and to study the pharmacokinetic profiles of the two compounds in beagle dogs. After rapid precipitation of protein by adding acetonitrile, the chromatographic separation of tofacitinib was completed, as well as M9 and upadacitinib (internal standard, IS) by using an Acquity BEH C18 (1.7 μm, 2.1 mm × 50 mm) column. A Xevo TQ-S triple quadrupole tandem mass spectrometer was employed to determine their concentrations under the positive ion pattern. Selective reaction monitoring (SRM) was used with ion transitions at m/z 313.12 → 148.97 for tofacitinib, m/z 329.10 → 137.03 for M9, and m/z 380.95 → 255.97 for IS, respectively. This assay demonstrated excellent linearity, and the ranges of calibration curves for both tofacitinib and M9 were 0.5–400 ng/mL. The new UPLC-MS/MS assay can reach the values (0.5 ng/mL) of lower limit of quantification (LLOQ) for both tofacitinib and M9. Both intra-day and inter-day accuracy of all analytes ranged from ?12.0% to 14.3%, while the precision was ≤13.2%. The recovery rate of all analytes was >88.5%, and more importantly there was no conspicuous matrix effect. In addition, the stability was consistent with the quantificative requirements of plasma samples under all conditions. Finally, the assay on UPLC-MS/MS is able to be employed to determine the pharmacokinetic characteristics of tofacitinib and its metabolite M9 in the plasma of beagle dogs after taking orally a dose of tofacitinib at 2 mg/kg.     

LC–MS–MS Study of the Pharmacokinetics of a 9-β-Dihydro-9,10-O-acetal Derivative of Docetaxel in Rats and Beagle Dogs

SHR110008 is a representative 9-β-dihydro-9,10-O-acetal taxane with greater anticancer activity and less toxicity than docetaxel. To support a preclinical study of its pharmacokinetics and to predict the effect of 9-β-dihydro-9,10-O-acetal modification on its pharmacokinetic properties, we have developed a sensitive and rapid liquid chromatographic–tandem mass spectrometric method for quantitative analysis of SHR110008 in rat and dog plasma. Plasma was extracted with ethyl acetate. The analytes were separated on a 150 × 4.6 mm i.d., 5 μm particle, reversed-phase C₁₈ column with 90:10 (v/v) methanol–0.1% formic acid as mobile phase at a flow rate of 0.3 mL min^?1. Detection was performed by triple-quadrupole tandem mass spectrometry in selected reaction monitoring (SRM) mode with an electrospray ionization source. The precursor-to-product ion transition m/z 933 → 142 was used. The method was validated for accuracy and precision, and linearity in the two matrices was good. Lower limits of quantification (LLOQ) in rat and dog plasma were 5 and 2 ng mL^?1, respectively. There were no stability-related problems in the procedure for analysis of SHR110008. The method was successfully used in a preclinical study of the pharmacokinetics of SHR110008 in rats and beagle dogs. The pharmacokinetics of SHR110008 were non-linear in rats and dogs. The elimination half-life ranged from 5.18 to 7.32 h for the rats and from 6.42 to 8.42 h for the dogs.     

Validation of an LC-MS/MS method for the quantitative determination of mavoglurant (AFQ056) in human plasma

A simple, sensitive, and selective liquid chromatography/tandem mass spectrometry method was validated for the identification and quantification of mavoglurant (AFQ056) in human plasma. The chromatographic separation was performed using a Cosmosil 5 C18 (150?×?4.6 mm, 5 μm) column at 40?±?0.5 °C with a mobile phase consisting of acetic acid in water (0.1 %, v/v)/methanol (10:90, v/v) with a flow rate of 1.0 mL/min followed by quantification with tandem mass spectrometry, operating with electrospray ionization in positive ion mode and applying multiple reaction monitoring. The validated method described in this paper presents high absolute recovery with precision and accuracy meeting the acceptance criteria. The method was precise and accurate for 2- and 10-fold dilution of samples. The method was validated using sodium heparin as specific anticoagulant, and the anticoagulant effect was tested by lithium heparin and K₃EDTA. The method was successfully cross-validated between two bioanalytical sites. The method was specific for mavoglurant within the given criteria for acceptance (apparent peak area at the retention time of mavoglurant in zero samples was less than 20 % compared with the mean peak area at LLOQ) in human plasma. The method was fully validated for the quantitative determination of mavoglurant in human plasma between the range of 2.00 and 2,500 ng/mL.     

Simultaneous determination of etonogestrel and ethinyl estradiol in human plasma by UPLC‐MS/MS and its pharmacokinetic study

A selective, sensitive and rapid ultra‐performance liquid chromatography tandem mass spectrometry method was developed and validated for the simultaneous determination of etonogestrel (ENG) and ethinyl estradiol (EE) in human plasma. The analytes and their deuterated internal standards, ENG‐d7 and EE‐d4, were extracted from plasma samples by solid‐phase extraction on HyperSep™ Retain PEP cartridges. The chromatographic analysis was performed on an Acquity UPLC HSS Cyano column, 100 Å (50 × 2.1 mm, 1.8 μm), column using gradient mobile phase, acetonitrile and 2.0 mm ammonium trifluoroacetate at 0–1.7 min (65:35, v/v) and 1.8–2.7 min (95:5, v/v) with 0.250 mL/min flow rate. Analytes and IS protonated precursor → product ion transitions (ENG, m/z 325.2 → 257.2; EE, m/z 530.2 → 171.2; ENG‐d7, m/z 332.2 → 263.2; EE‐d4, m/z 534.2 → 171.2) were monitored on a Triple Quadrupole Mass spectrometer (TQMS), operating in multiple reaction monitoring and positive ionization mode. The calibration curves were established at 10.00–2500 pg/mL for ENG and 1.500–150.0 pg/mL for EE with a correlation coefficient (r²) ≥0.9996 for both. The validated method was successfully applied to support a bioequivalence study of 0.15 mg ENG and EE 0.03 mg tablet formulation, administered in 24 healthy Indian females. Method reliability was assessed by reanalysis of 94 incurred study samples.     

Rapid quantification of levosulpiride in human plasma using RP‐HPLC‐MS/MS for pharmacokinetic and bioequivalence study

A rapid and validated method for analysis of levosulpiride in human plasma using liquid chromatography coupled to tandem mass spectrometry was developed. Levosulpiride and tiapride (IS, internal standard) were extracted from alkalized plasma samples with ethylacetate and separation by RP‐HPLC. Detection was performed by positive ion electrospray ionization in multiple‐reaction monitoring mode, monitoring the transitions m/z 342.1 → m/z 112.2 and m/z 329.1 → m/z 213.2, for quantification of levosulpiride and IS, respectively. The standard calibration curves showed good linearity within the range of 2–200 ng/mL (r² ≥ 0.9990). The lower limit of quantitation was 2 ng/mL. The retention times of levosulpiride (0.63 min) and IS (0.66 min) presented a significant time saving benefit of the proposed method. No significant metabolic compounds were found to interfere with the analysis. This method offered good precision and accuracy and was successfully applied for the pharmacokinetic and bioequivalence study of a 25 mg of levosulpiride tablet in 24 healthy Korean volunteers. Copyright © 2009 John Wiley & Sons, Ltd.     

LC‐MS/MS for Determination of Paclitaxel in Rat Tissues: Application to a Biodistribution Study of Paclitaxel Nanoliposome Modified by PEO‐PPO‐PEO Triblock Copolymers

Abstract

A liquid chromatography‐tandem triple‐quadrupole mass spectrometry assay to quantify palitaxel in rat tissue homogenates containing paclitaxel nanoliposome (PTX‐NLP) modified by PEO-PPO-PEO triblock copolymers was developed and validated. Liquid–liquid extraction with tert‐butyl methyl ether was used for preparation of tissue samples and docetaxel was used as the internal standard. Paclitaxel and docetaxel were separated on a 200 mm×4.6 mm×5 µm C₁₈ column and quantified using a triple‐quadrupole mass spectrometer operating in positive ion electrospray selective reaction monitoring mode (ESI⁺‐SRM) with a total run time of 6.0 min. The peak area of the m/z 876.3→307.9 transition of paclitaxel is measured vs. that of the m/z 830.3→549.1 transition of docetaxel to generate the standard curves. The standard curves were linear over the concentration range of 0.2–2000 ng/mL for different tissues. The method had high extraction recovery (>90%) and accuracy (>90%) with the intraday and inter‐day precision <15%. Frozen stability, freeze‐thaw stability, extracted stability, and solution stability under ambient temperature were examined, which indicated the tissue samples should be extracted within 5 days and avoid being frozen and thawed repeatedly over 5 times, extracted samples after evaporation could be stored at ?20°C for 20 days without drug degradation, also, no degradation was observed after solution samples were left out at ambient temperature for 24 h. This assay was used to support an in vivo biodistribution study of paclitaxel nanoliposome modified by PEO-PPO-PEO triblock copolymers in rats.     

Rapid quantitative analysis of etoricoxib in human plasma by UPLC‐MS/MS and application to a pharmacokinetic study in Chinese healthy volunteers

A selective and sensitive liquid chromatography–tandem mass spectrometry method was developed for simultaneous determination of etoricoxib in human plasma. Chromatography was performed on an Acquity UPLC HSS T3 column (1.8 μm, 50 × 2.1 mm), with a flow rate of 0.600 mL/min, using a gradient elution with acetonitrile and water which contained 2 mm ammonium acetate as the mobile phase. Detection was carried out on Triple QuadTM 5500 mass spectrometer under positive‐ion multiple reaction monitoring mode. The respective mass transitions used for quantification of etoricoxib and etoricoxib‐d3 were m/z 359.0 → 280.1 and m/z 362.0 → 280.2. Calibration curves were linear over the concentration range of 5–5000 ng/mL. The validated method was applied in the pharmacokinetic study of etoricoxib in Chinese healthy volunteers under fed and fasted conditions. After a single oral dose of 120 mg, the main pharmacokinetic parameters of etoricoxib in fasted and fed groups were respectively as follows: peak concentration, 2364.78 ± 538.01 and 1874.55 ± 367.90 ng/mL; area under the concentration–time curve from 0 to 120 h, 44,605.53 ± 15,266.66 and 43,516.33 ± 12,425.91 ng h/mL; time to peak concentration, 2.00 and 2.50 h; and half‐life, 24.08 ± 10.06 and 23.64± 6.72 h. High‐fat food significantly reduced the peak concentration of etoricoxib (p = 0.001) but had no effect on the area under the concentration–time curve.     

High‐performance liquid chromatography tandem mass spectrometry method for quantification of endothelin receptor antagonist drug,ambrisentan, in human plasma and its application in a pharmacokinetic study

A simple and sensitive liquid chromatography tandem mass spectrometry method has been developed for the quantification of ambrisentan (AMB) in human plasma using midazolam (MID) as an internal standard (IS). Chromatographic separation was performed using a Beta Basic‐8 (50 × 4.6 mm, 5 µm) column with an isocratic mobile phase. AMB and MID were detected with proton adducts at m/z 379.09 → 303.12 and 326.15 → 291.14 in multiple reaction monitoring‐positive mode, respectively. A solid‐phase extraction method was used for extraction of the analyte and IS from the plasma samples. The method was shown to be reproducible and reliable with within‐run precision <11%, between‐run precision <14% and linear concentration range from 10.0 to 2000.2 ng/mL, with a correlation coefficient (r²) of >0.995. The method was successfully applied to a pharmacokinetic study of oral administration of AMB (10 mg) in 24 healthy Indian male human volunteers under fasting conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of Doxapram Hydrochloride in Rabbit Plasma by LC-MS-MS and Its Application

A sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS-MS) method for determination of doxapram hydrochloride in rabbit plasma was developed. After addition of urapidil hydrochloride as internal standard (IS), protein precipitation by 10% trichloroacetic acid in methanol (w/v) was used as sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm × 50 mm, 3.5 μm) column with acetonitrile–water as mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used for quantification using target fragment ions m/z 378.9 → 291.8 for doxapram hydrochloride and m/z 387.9 → 204.6 for the IS. Calibration plots were linear over the range of 2–1000 ng mL^?1 for doxapram hydrochloride in plasma. Lower limit of quantitation (LLOQ) for doxapram hydrochloride was 2 ng mL^?1. Mean recovery of doxapram hydrochloride from plasma was in the range 83.7–91.5%. RSD of intra-day and inter-day precision were less than 9%, respectively. This method is simple and sensitive enough to be used in pharmacokinetic research for determination of doxapram hydrochloride in rabbit plasma.