Determination of toosendanin in rat plasma by ultra‐performance liquid chromatography–electrospray ionization–mass spectrometry and its application in a pharmacokinetic study

Toosendanin (TSN) is a major triterpenoid existing in Melia toosendan, which has been used as a digestive tract parasiticide and insecticide but with serious hepatotoxicity. An ultra‐performance liquid chromatography–electrospray ionization–mass spectrometry method was developed for determination of TSN in rat plasma. Plasma samples were separated on Acquity UPLC^TM BEH C₁₈ column with acetonitrile and water as flow phase by gradient elution and determined by quadrupole mass spectrometer in negative selective ion monitoring mode. Usolic acid was used as internal standard. The calibration curves were linear over 0.02–3.0 µg/mL for TSN with a lower limit of quantification (LLOQ) of 20 ng/mL in rat plasma. The extraction recoveries of TSN were within 74.3–80.7% with an accuracy of 94.5–108.9%. The intra‐ and inter‐day precision values of the assay at three quality control levels were 8.8–13.8% and <13.9% at LLOQ level, respectively. The method was successfully applied to a pharmacokinetic study of TSN in rats after a single intravenous and oral administration of 2 and 60 mg/kg. The shorter T_max, higher V_d and Cl of TSN after oral administration indicated that TSN could be absorbed, distributed and eliminated quickly in rats in vivo. The absolute bioavailability of TSN after oral administration was 9.9%. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of astragaloside III in rat plasma by liquid chromatography–tandem mass spectrometry and its application to a rat pharmacokinetic study

Astragaloside III (AST III), a naturally occurring saponin compound isolated from Radix Astragali, has been demonstrated to have anti‐gastric ulcer, immunomodulatory and antitumor effects. To evaluate its pharmacokinetics in rats, a rapid, sensitive and specific high‐performance liquid chromatography–tandem mass spectrometric (HPLC‐MS/MS) method has been developed and validated for the quantification of astragaloside III in rat plasma. Samples were pretreated using a simple protein precipitation with methanol–acetonitrile (50:50, v/v) and the chromatographic separation was performed on a C₁₈ column by a gradient elution using a mobile phase consisting of water containing 0.1% formic acid and acetonitrile containing 0.1% formic acid. Astragaloside III and the internal standard (buspirone) were detected using a tandem mass spectrometer in positive multiple reaction monitoring mode. Method validation revealed excellent linearity over the range of 5.00–5000 ng/mL together with satisfactory intra‐ and inter‐day precision, accuracy and recovery. Stability testing showed that astragaloside III spiked into rat plasma was stable for 24 h at 20°C temperature, for up to 30 days at ?80°C, and during three freeze–thaw cycles. The method was successfully used to investigate the pharmacokinetic profile of AST III after oral (10 mg/kg) and intravenous (1.0 mg/kg) administration in rats. The oral absolute bioavailability of AST III was calculated to be 4.15 ± 0.67% with an elimination half‐life value of 2.13 ± 0.11 h, suggesting its poor absorption and/or strong metabolism in vivo. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination and validation of chikusetsusaponin IVa in rat plasma by UPLC‐MS/MS and its application to pharmacokinetic study

A novel, sensitive and rapid ultra‐performance liquid chromatography–tandem mass spectrometric method for the quantification of chikusetsusaponin IVa (CHS‐IVa) in rat plasma was established and validated. Plasma samples were pre‐treated by precipitation of protein with acetonitrile and chromatographed on a Waters Symmetry C₁₈ analytical column (4.6 × 50 mm, i.d., 3.5 μm) using a mobile phase consisting of methanol and water containing 0.05% formic acid (55:45, v/v) at a flow rate of 0.4 mL/min. The deprotonated molecular ions [M ? H]^– were employed in electrospray negative ionization mode and selected reaction monitoring transitions were performed for detection. The calibration curves exhibited good linearity (r > 0.99) over the range of 0.5–1000 ng/mL for CHS‐IVa. The recoveries of CHS‐IVa were >92.5% and exhibited no severe matrix effect. This method was successfully applied in the pharmacokinetic study of CHS‐IVa in rats. For oral administration, the plasma concentrations of CHS‐IVa increased to a peak value at 0.35 ± 0.14 h, followed by a gradual decrease to the lower limit of quantitation in 24 h. For intravenous administration, the plasma concentrations of CHS‐IVa decreased quickly (t_1/2, 1.59 ± 0.25 h). The absolute bioavailability of CHS‐IVa in rats was 8.63%. Copyright © 2016 John Wiley & Sons, Ltd.     

Quantitative determination of rupestonic acid in rat plasma by high‐performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A sensitive and specific high‐performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC‐ESI‐MS/MS) method was developed and validated for determination of rupestonic acid in rat plasma. Protein precipitation method was used to extract rupestonic acid and the internal standard (IS) warfarin sodium from rats plasma. The chromatographic separation was performed on an Agela Venusil XBP Phenyl column with an isocratic mobile phase consisting of methanol–0.1% formic acid in water (40:60, v/v), pumped at 0.4 mL/min. Rupestonic acid and the internal standard (IS) warfarin sodium were detected at m/z 247.2 → 203.1 and 307.1 → 161.3 in positive ion and multiple reaction monitoring mode respectively. The standard curves were linear over the concentration range of 2.5–5000 ng/mL (r² > 0.99). The within‐day and between‐day precision values for rupestonic acid at four concentrations were 4.7–5.7 and 4.4–8.7%, respectively. The method described herein was fully validated and successfully applied to the pharmacokinetic study after an intravenous administration of rupestonic acid in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of a liquid chromatography–tandem mass spectrometry method for quantitation of indomethacin in rat plasma and its application to a pharmacokinetic study in rats

A highly sensitive and rapid bioanalytical method has been developed and validated for the estimation of indomethacin in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves a simple liquid–liquid extraction of indomethacin and phenacetin (internal standard, IS) from rat plasma with acetonitrile. Chromatographic separation was achieved with 0.2% formic acid–acetonitrile (25:75, v/v) at a flow rate of 0.60 mL/min on an Atlantis dC₁₈ column with a total run time 3.0 min. The MS/MS ion transitions monitored were 357.7 → 139.1 for indomethacin and 180.20 → 110.10 for IS. Method validation and pharmacokinetic study plasma analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.51 ng/mL and the linearity was observed from 0.51 to 25.5 ng/mL. The intra‐ and inter‐day precisions were in the range of 1.00–10.2 and 5.88–9.80%, respectively. This novel method has been applied to an oral pharmacokinetic study in rats. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

Determination of eurycomanone in rat plasma using hydrophilic interaction liquid chromatography–tandem mass spectrometry for pharmacokinetic study

In this study, a rapid, sensitive, and reliable hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) method for the determination of eurycomanone in rat plasma was developed and validated. Plasma samples were pretreated with a protein precipitation method and quercitrin was used as an internal standard (IS). A HILIC silica column (2.1 × 100 mm, 3 μm) was used for hydrophilic‐based chromatographic separation, using the mobile phase of 0.1% formic acid with acetonitrile in gradient elution at a flow rate of 0.25 mL/min. Precursor–product ion pairs for multiple‐reaction monitoring were m /z 409.1 → 391.0 for eurycomanone and m /z 449.1 → 303.0 for IS. The linear range was 2–120 ng/mL. The intra‐ and inter‐day accuracies were between 95.5 and 103.4% with a precision of <4.2%. The developed method was successfully applied to the pharmacokinetic analysis of eurycomanone in rat plasma after oral dosing with pure compound and E. longifolia extract. The C _max and AUC_0–t , respectively, were 40.43 ± 16.08 ng/mL and 161.09 ± 37.63 ng h/mL for 10 mg/kg eurycomanone, and 9.90 ± 3.97 ng/mL and 37.15 ± 6.80 ng h/mL for E. longifolia extract (2 mg/kg as eurycomanone). The pharmacokinetic results were comparable with each other, based on the dose as eurycomanone.     

Simultaneous determination of four secoiridoid and iridoid glycosides in rat plasma by ultra performance liquid chromatography–tandem mass spectrometry and its application to a comparative pharmacokinetic study

A simple, reliable and rapid ultra‐performance liquid chromatography–tandem mass spectrometry method was developed and validated for the simultaneous quantification of four secoiridoid (gentiopicroside, swertiamarin, sweroside) and iridoid glycosides (loganic acid), the bio‐active ingredients in rat plasma. After liquid–liquid extraction, chromatographic separation was accomplished on a Shim‐pack XR‐ODS column with a mobile phase consisting of methanol and 0.1% formic acid in water. A triple quadrupole tandem mass spectrometry equipped with an electrospray ionization source was used as detector operating both in positive and negative ionization mode and operated by multiple‐reaction monitoring scanning. The lower limits of quantitation were 0.25–30 ng/mL for all the analytes. Both intra‐day and inter‐day precision and accuracy of analytes were well within acceptance criteria (±15%). The mean extraction recoveries of analytes and internal standard (amygdalin) from rat plasma were all >71.4%. The validated method was successfully applied to a comparative pharmacokinetic study of four analytes in rat plasma between normal and arthritic rats after oral administration of Huo Luo Xiao Ling Dan and Gentiana macrophylla extract, respectively. Results showed significant differences in pharmacokinetic properties of the analytes among the different groups. Copyright © 2015 John Wiley & Sons, Ltd.     

An ultraperformance liquid chromatography–tandem mass spectrometry method for determination of anastrozole in human plasma and its application to a pharmacokinetic study

A fast, selective and sensitive ultraperformance liquid chromatography–tandem mass spectrometry method was developed for determination and pharmacokinetic study of anastrozole in human plasma. Plasma sample pretreatment involved a one‐step extraction with diethyl ether of 500 µL plasma. The chromatographic separation was carried out on an Acquity UPLC^TM BEH C₁₈ column with a mobile phase consisting of methanol–10 mmol/L ammonium acetate (75:25, v/v) at a flow rate of 0.30 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring via electrospray ionization source with positive mode. A high throughput was achieved with a run time of 1.5 min per sample. The standard curve for anastrozole was linear (r² ≥ 0.99) over the concentration range of 0.0550–27.5 ng/mL with a lower limit of quantification of 0.0550 ng/mL. The intra‐ and inter‐day precision (relative standard deviation) values were not higher than 14% and the accuracy (relative error) was within ±3.2% at three quality control levels. This simple, fast and highly sensitive method was fully validated and successfully applied to a clinical pharmacokinetic study of anastrozole in healthy volunteers after oral administration. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantitative determination of dipyridamole in human plasma by high‐performance liquid chromatography–tandem mass spectrometry and its application to a pharmacokinetic study

Dipyridamole is a classic platelet inhibitor which has been a key medicine in clinical therapy of thrombosis and cerebrovascular disease. A rapid, selective and convenient method using high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) was developed for determination of dipyridamole in human plasma. After protein precipitation of 200 μL plasma with methanol, dipyridamole and diazepam (internal standard) were chromatographed on an Ultimate? XB‐C₁₈ (50 × 2.1 mm i.d, 3 μ) column with the mobile phase consisting of methanol–ammonium acetate (5 mM ; 80 : 20, v/v) at a flow rate of 0.25 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode via positive eletrospray ionization source (ESI⁺). The retention times of dipyridamole and diazepam were 1.4 and 1.2 min, respectively. The method was validated over a concentration range of 0.0180–4.50 μg/mL (r² ≥ 0.99) with a lower limit of quantitation (LLOQ) of 0.0180 μg/mL for dipyridamole. The intra‐ and inter‐day precisions (RSD) of the assay at all three QC levels were 1.6–12.7% with an accuracy (RE) of ?4.3–1.9%, which meets the requirements of the FDA guidance. The HPLC‐MS/MS method herein described was proved to be suitable for pharmacokinetic study of sustained‐release dipyridamole tablet in volunteers after oral administration. Copyright © 2009 John Wiley & Sons, Ltd.     

Ultra‐high pressure liquid chromatography–tandem mass spectrometry method for the determination of omarigliptin in rat plasma and its application to a pharmacokinetic study in rats

Omarigliptin is a novel long‐acting dipeptidyl peptidase‐4 inhibitor used for the treatment of type 2 diabetes. In this work, a sensitive and selective ultra‐high pressure liquid chromatography tandem mass spectrometry method was developed and validated for the determination of omarigliptin in rat plasma. Sample preparation was performed by protein precipitation with acetonitrile. Chromatographic separation of analytes was achieved on an RRHD Eclipse Plus C18 column (2.1 × 50 mm, 1.8 μm), using gradient mobile phase (0.1% formic acid–acetonitrile) at a flow rate of 0.4 mL/min. Detection was performed in multiple reaction monitoring mode, with target fragment ions m/z 399.1 → 152.9 for omarigliptin and m/z 237.1 → 194 for the internal standard. The total run time was 4 min. Retention time of omarigliptin and internal standard was 1.25 and 2.12 min, respectively. Relative standard deviation (%) of the intra‐ and inter‐day precision was below 10.0%, and accuracy was between 97.9% and 105.3%. Calibration curve was established over the range 2–5000 ng/mL with good linearity. The lower limit of quantification and limit of detection of omarigliptin were 2 and 0.25 ng/mL, respectively. Mean recoveries were in the range 87.3–95.1% for omarigliptin. No matrix effect was observed in this method. This novel method has been successfully applied to a pharmacokinetic study of omarigliptin in rats. The absolute bioavailability of omarigliptin was identified as high as 87.31%.     

Quantification and pharmacokinetics of crizotinib in rats by liquid chromatography–tandem mass spectrometry

Crizotinib is a small molecule inhibitor of anaplastic lymphoma kinase (ALK) and can be used to treat ALK‐positive nonsmall‐cell lung cancer. A rapid and simple high‐performance liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the quantification of crizotinib in rat plasma using a chemical synthetic compound buspirone as the internal standard (IS). The plasma samples were pretreated by a simple protein precipitation with methanol–acetonitrile (1:1, v/v). Chromatographic separation was successfully achieved on an Agilent Zorbax XDB C₁₈ column (2.1 × 50 mm, 3.5 µm). The gradient elution system was composed of 0.1% formic acid aqueous solution and 0.1% formic acid in methanol solution. The flow rate was set at 0.50 mL/min. The multiple reaction monitoring was based on the transitions of m/z = 450.3 → 177.1 for crizotinib and 386.2 → 122.2 for buspirone (IS). The assay was successfully validated to demonstrate the selectivity, matrix effect, linearity, lower limit of quantification, accuracy, precision, recovery and stability according to the international guidelines. The lower limit of quantification was 1.00 ng/mL in 50 μL of rat plasma. This LC‐MS/MS assay was successfully applied to the quantification and pharmacokinetic study of crizotinib in rats after intravenous and oral administration of crizotinib. The oral absolute bioavailability of crizotinib in rats was 68.6 ± 9.63%. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative determination of meloxicam in dog plasma by high performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A rapid, selective and sensitive high‐performance liquid chromatography–tandem mass spectrometry (HPLC‐MS/MS) method was developed to determine meloxicam in beagle dog plasma. Sample pretreatment involved a one‐step protein precipitation with methanol of 0.1 mL plasma. Analysis was performed on a Venusil ASB‐C₁₈ column with mobile phase consisting of methanol–water (containing 0.1% formic acid) (75:25, v/v). The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode via electrospray ionization source. Each plasma sample was chromatographed within 4.1 min. The linear calibration curves for meloxicam was obtained in the concentration range of 10.3–4.12 × 10³ ng/mL (r ≥ 0.99). The intra‐ and inter‐day precisions (relative standard deviation) were ≤ 15%, and accuracy (relative error) was within ±7.3%. The method herein described was fully validated and successfully applied to the pharmacokinetic study of meloxicam tablets in beagle dog.     

Development and validation of high-performance liquid chromatography/electrospray ionization mass spectrometry for assay of madecassoside in rat plasma and its application to pharmacokinetic study

A rapid, sensitive and specific high-performance liquid chromatography/electrospray ionization mass spectrometric (LC-ESI-MS) method was developed and validated for the quantification of madecassoside, a major active constituent of Centella asiatica (L.) Urb. herbs, in rat plasma. With paeoniflorin as an internal standard (IS), a simple liquid-liquid extraction process was employed for the plasma sample preparation. Chromatographic separation was achieved within 6 min on a Shim-pack CLC-ODS column using acetonitrile and water (60:40, v/v) containing 0.1% (v/v) formic acid as the mobile phase. The detection was performed by MS with electrospray ionization interface in negative selected ion monitoring (SIM) mode. The linear range was 11-5500 ng/mL with the square regression coefficient (r(2) ) of 0.9995. The lower limit of quantification was 11 ng/mL. The intra- and inter- day precision ranged from 4.99 to 9.03%, and the accuracy was between 95.82 and 111.80%. The average recoveries of madecassoside and IS from spiked plasma samples were >92%. The developed method was successfully applied to the pharmacokinetic study of madecassoside in rats after an oral administration.     

Quantitative determination of enzalutamide,an anti‐prostate cancer drug,in rat plasma using liquid chromatography–tandem mass spectrometry,and its application to a pharmacokinetic study

This report details a method using liquid chromatography–tandem mass spectrometry (LC‐MS/MS) that allows one to determine the concentration of an atypical anticancer drug, enzalutamide, in rat plasma. Specifically, this method involves the addition of an acetonitrile and bicalutamide (internal standard) solution to plasma samples. Following centrifugation of this mixture, an aliquot of the supernatant was directly injected into the LC‐MS/MS system. Separation was achieved using a column packed with octadecylsilica (5 µm, 2.1 × 50 mm) with 10 mM ammonium acetate in acetonitrile as the mobile phase; detection was accomplished using MS/MS by multiple‐reaction monitoring via an electrospray ionization source. This method demonstrated a linear standard curve (r = 0.997) over a concentration range of 0.001–1 µg/mL, as well as an intra‐ and inter‐assay precision of 2.7 and 5.1%, respectively, and an accuracy range from 100.8 to 105.6%. The lower limit of quantification was 1.0 ng/mL in 50 μL of rat plasma sample. We also demonstrated that this analytical method could be successfully applied to the pharmacokinetic study of enzalutamide in rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Quantitative analysis of costunolide and dehydrocostuslactone in rat plasma by ultraperformance liquid chromatography–electrospray ionization–mass spectrometry

Costunolide and dehydrocostuslactone are well‐known sesquiterpene lactones contained in many plants used as popular herbs, such as Saussurea lappa and Laurus novocanariensis, and have been considered as potential candidates for the treatment of various types of tumor. In the present work, a sensitive UPLC‐MS/MS for the quantification of costunolide and dehydrocostuslactone in biological matrices has been developed. The method is based on protein precipitation with acetonitrile followed by isocratic ultraperformance liquid chromatographic separation using methanol–formic acid (0.1% in water; 70:30, v/v) mobile phase. Detection was performed by ESI mass spectrometry in MRM mode with the precursor‐to‐product ion transitions m/z 233–187 and m/z 231–185, respectively. The calibration curves of analytes showed good linearity within the established range 0.19–760 ng/mL for costunolide and 0.23–908 ng/mL for dehydrocostuslactone. The lower limits of quantification of costunolide and dehydrocostuslactone were found to be 0.19 and 0.23 ng/mL, respectively. The intra‐day and inter‐day presicions of this method for the entire validation were less than coefficient of variation of 7% and the accuracy was within ±8% (relative error). The mean extraction recoveries were 73.8 and 75.3%, respectively. The method was found to be precise, accurate and specific during the study, and was successfully used to analyze the pharmacokinetics of costunolide and dehydrocostuslactone. Copyright © 2010 John Wiley & Sons, Ltd.     

Determination of cyclobenzaprine in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry and its application in a pharmacokinetic study

A sensitive, rapid and simple liquid chromatography–electrospray ionization mass spectrometry (LC‐ESI‐MS/MS) method was developed for the quantitative determination of cyclobenzaprine in human plasma, to study the pharmacokinetic behavior of cyclobenzaprine capsule in healthy Chinese volunteers. With escitalopram as the internal standard (IS), sample pretreatment involved a one‐step liquid–liquid extraction using saturated sodium carbonate solution and hexane–diethyl ether (3:1, v/v). The separation was performed on an Ultimate XB‐CN column (150 × 2.1 mm, 5 µm). Isocratic elution was applied using acetonitrile–water (40:60, v/v) containing 10 m M ammonium acetate and 0.1% formic acid. The detection was carried out on a triple‐quadrupole tandem mass spectrometer in multiple reaction monitoring mode via electrospray ionization. The ion‐pairs including m/z 276.2–216.2 for cyclobenzaprine and m/z 325.2–109.1 for IS were used for monitoring. Linear calibration curves were obtained over the range of 0.049–29.81 ng/mL with the lower limit of quantification at 0.049 ng/mL. The intra‐ and inter‐day precision showed ≤6.5% relative standard deviation. The established method laid the groundwork for follow‐up studies and provided basis for the clinical administration of cyclobenzaprine. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and validation of a liquid chromatography/tandem mass spectrometry assay for the quantification of methyl protodioscin in rat plasma: application to a pharmacokinetic study

A high performance liquid chromatography/tandem mass spectrometry assay was first developed and validated for the quantification of methyl protodioscin (MPD), a natural furostanol saponin with distinct antitumor activity, in rat plasma with 17alpha-ethinylestradiol as internal standard (IS). Methanol-mediated protein precipitation was employed for plasma sample pretreatment. The separation was achieved on a C(18) column (150 x 4.6 mm, i.d., 5 microm) by isocratic elution with methanol-water (72:28, v/v) as mobile phase at a flow rate of 1.0 mL/min. Ion acquisition was performed in selective reaction monitoring positive mode by monitoring the transition of m/z 1085.7 --> 1053.7 for MPD, and in selective ion monitoring negative mode by monitoring the deprotonated ion m/z 295.5 for IS. The assay was linear over the concentration range of 2.024-270.0 microg/mL with 2.024 microg/mL as the lower limit of quantification. It was specific, accurate, precise and reproducible with intra- and inter-run RSD <8.3% and RE between -11.5 and 12.8%. The assay was successfully applied to a preclinical pharmacokinetic study after an intravenous dose of 40 mg/kg MPD to rats.     

Quantification of mequitazine in human plasma by gas chromatography– quadrupole mass spectrometry and its application to a human pharmacokinetic study

A specific and sensitive gas chromatography–mass spectrometry (GC‐MS) with quadrupole mass analyzer type was developed and validated for the quantitative analysis of mequitazine in human plasma. After liquid–liquid extraction of plasma samples containing mequitazine and promethazine (internal standard, IS) using hexane with pH adjustment, the extract was evaporated and an aliquot of reconstituted residue was injected into the GC‐MS system. The assay showed linearity over a concentration range from 1 to 50 ng/mL. Intra‐ and inter‐day precision for mequitazine was <9.09 and 9.29%, respectively, and intra‐ and inter‐day accuracy ranged from ?7.97 to 9.05% and from ?1.51 to 7.89%, respectively. The lower limit of quantification was 1 ng/mL in the present assay. The developed analytical method was successfully applied to a pharmacokinetic study after a single oral administration of mequitazine in human subjects. Copyright © 2015 John Wiley & Sons, Ltd.     

Determination of PF‐04620110, a novel inhibitor of diacylglycerol acyltransferase‐1, in rat plasma using liquid chromatography–tandem mass spectrometry and its application in pharmacokinetic studies

In this study, we developed a method for the determination of PF‐04620110 (2‐{(1r,4r)‐4‐[4‐(4‐amino‐5‐oxo‐7,8‐dihydropyrimido[5,4‐f][1,4]oxazepin‐6(5H)‐yl)phenyl]cyclohexyl}acetic acid), a novel diacylglycerol acyltransferase 1 (DGAT‐1) inhibitor, in rat plasma and validated it using liquid chromatography–tandem mass spectrometry (LC‐MS/MS). Rat plasma samples were processed following a protein precipitation method by using acetonitrile and were then injected into an LC‐MS/MS system for quantification. PF‐04620110 and imipramine (internal standard) were separated using a Hypersil Gold C₁₈ column, with a mixture of acetonitrile and 10 mm ammonium formate (90:10, v/v) as the mobile phase. The ion transitions monitored in positive‐ion mode [M + H]⁺ of multiple‐reaction monitoring were m/z 397.0 → 260.2 for PF‐04620110 and m/z 280.8 → 86.0 for imipramine. The detector response was specific and linear for PF‐04620110 at concentrations within the range 0.05–50 µg/mL and the signal‐to‐noise ratios for the samples were ≥10. The intra‐ and inter‐day precision and accuracy of the method matched the acceptance criteria for assay validation. PF‐04620110 was stable under various processing and/or handling conditions. PF‐04620110 concentrations in the rat plasma samples could be measured up to 24 h after intravenous or oral administration of PF‐04620110, suggesting that the assay is useful for pharmacokinetic studies in rats. Copyright © 2013 John Wiley & Sons, Ltd.