Development and validation of a simple and sensitive high‐resolution LC/MS method for determination of PF‐04620110 in dog plasma: Application to a pharmacokinetic study

In this study, a more sensitive and reliable quantitative method based on ultra‐high performance liquid chromatography coupled with Q‐Exactive‐Orbitrap‐MS in full‐mass scan was developed and validated for the determination of PF‐04620110 in dog plasma. After protein precipitation with acetonitrile, the sample separations were carried out on an Acquity BEH C₁₈ column with 1 mm ammonium acetate in water and acetonitrile containing 0.1% acetic acid as mobile phase, at a flow rate of 0.4 mL/min. The assay showed excellent linearity over the concentration range of 1–2000 ng/mL with correlation coefficient >0.9980 (r > 0.9980). The LLOQ was 1 ng/mL. The inter‐ and intra‐day precision (RSD, %) was within 9.69% while the accuracy (RE, %) was in the range of ?8.59–11.24%. The extraction recovery was >85.37% and the assay was free of matrix effects. PF‐04620110 was demonstrated to be stable under various processing and handing conditions. The validated method was successfully applied to the pharmacokinetic study of PF‐04620110 in dogs and the results revealed that PF‐04620110 was slowly eliminated from plasma with a clearance of 60.81 ± 7.11 mL/h/kg for intravenous administration and 81.44 ± 25.79 mL/h/kg for oral administration. The oral bioavailability was determined to be 77.89% in dogs.     

Pharmacokinetics,bioavailability and metabolism of scopoletin in dog by ultra‐high‐performance liquid chromatography combined with linear ion trap–Orbitrap tandem mass spectrometry

A highly sensitive and selective method based on ultra‐high‐performance liquid chromatography combined with linear ion trap–Orbitrap tandem mass spectrometry (UHPLC–LTQ–Orbitrap–MS) has been developed and validated for the determination of scopoletin in dog plasma. The analyte was extracted from plasma samples using acetonitrile and separated on an Acquity UPLC BEH C₁₈ column (50 × 2.1 mm, 1.7 μm) with 0.05% ammonium hydroxide and acetonitrile as mobile phase. The developed method was linear over the concentration range of 1–500 ng/mL, with a correlation coefficient >0.9988. The intra‐ and inter‐day precisions (RSD) were <8.93% while the accuracy (RE) ranged from ?6.50 to 8.12%. Extraction recovery, matrix effect and stability for dog plasma samples were within the required limits. The validated method has been successfully applied to investigate the pharmacokinetics and metabolism of scopoletin in dog plasma after intravenous (1 mg/kg) and oral (10, 25, 50 mg/kg) administration. The results revealed that (a) scopoletin showed short elimination half‐life in dog; (b) its oral bioavailability was low (within the range of 5.69–7.08%); (c) scopoletin showed dose‐independent pharmacokinetic profiles in dog plasma over the dose range of 10–50 mg/kg; and (d) glucuronidation was the predominant metabolic pathway in dog.     

Determination of d‐limonene in mice plasma and tissues by a new GC–MS/MS method: Comparison of the pharmacokinetics and tissue distribution by oral and inhalation administration in mice

The aim of the present study was to develop a method based on gas chromatography–tandem mass spectrometry (GC–MS/MS) to determine and quantify the d ‐limonene in mouse plasma and tissue samples. This new method was validated for the quantification of d ‐limonene with the linearity ranges 1.0–1000.0 ng/mL (r² > 0.9952) for plasma samples and 5.0–5000.0 ng/g (r² > 0.9940) for tissue samples. The intra‐ and inter‐day assay of precisions in plasma and tissues were <13.4% and the accuracies were within 91.1–105.8%. In the oral/inhalation administration pharmacokinetics and tissue distribution studies, the main pharmacokinetic parameters were the peak concentration = (97.150 ± 34.450)/(4336.415 ± 1142.418) ng/mL, the area under the curve = (162.828± 27.447)/(2085.721 ± 547.787) h ng/mL and the half‐life = (3.196 ± 0.825)/(0.989 ± 0.095) h. The tissue distribution of d ‐limonene in mice after oral/inhalation administration demonstrated a decreasing tendency in different tissues (liver > kidney > heart > lung > spleen).     

A validated LC–MS/MS method for the quantification of capivasertib in dog plasma: Application to its pharmacokinetics study

In this study, a simple and reliable liquid chromatography tandem mass spectrometric method was first developed for the determination of capivasertib in dog plasma with ipatasertib as internal standard. The plasma samples were deproteinated using acetonitrile. An Acquity BEH C₁₈ column (1.7 μm, 2.1 × 50 mm) maintained at 40°C was used for chromatographical separation, with water containing 0.1% formic acid and acetonitrile as mobile phase. Multiple reaction monitoring transitions were m/z 429.2 > 135.1 for capivasertib and m/z 458.2 > 387.2 for ipatasertib, respectively. Excellent linearity was achieved in the concentration range of 1–1,000 ng/ml with a correlation coefficient of >0.9981. The lower limit of quantification was 1 ng/ml. The extraction recovery of capivasertib from dog plasma was >85.81% and no significant matrix effect was found. The intra- and inter-day precision was <9.58% and the accuracy ranged from −10.60% to 12.50%. The validated method was further applied to the pharmacokinetic study of capivasertib in dog plasma after single oral (5 mg/kg) and intravenous (1 mg/kg) administrations. The results revealed that capivasertib was rapidly absorbed into plasma with good bioavailability (47.04%) and low clearance.     

Simultaneous determination of evobrutinib and its metabolite evobrutinib‐diol in dog plasma by liquid chromatography combined with electrospray ionization tandem mass spectrometry

A rapid and sensitive liquid chromatography hyphenated with electrospray ionization tandem mass spectrometric method (LC–ESI–MS/MS) was developed and validated for simultaneous determination of evobrutinib and evobrutinib‐diol in dog plasma. The plasma sample was processed using acetonitrile and chromatographic separation was carried out on a Waters Acquity BEH C₁₈ column (50 × 2.1 mm, 1.7 μm). The mobile phase was composed of 0.1% formic acid and acetonitrile, with an optimized gradient elution at a flow rate of 0.4 mL/min. Detection was accomplished in selective reaction monitoring mode via electrospray ionization interface operated in positive ion mode. The precursor‐to‐product transitions for quantification were m/z 430.2 → 98.1 for evobrutinib, m/z 464.2 → 98.1 for evobrutinib‐diol and m/z 441.2 → 138.1 for ibrutinib (internal standard). The developed assay was linear over the tested concentration ranges with correlation coefficient >0.995. The LLOQ was 0.1 ng/mL for both analytes. The inter‐ and intra‐day precisions were <9.65% and the accuracy ranged from ?3.94 to 6.37%. The extraction recovery was >85.41% and no significant matrix effect was observed. The developed assay was successfully applied to the pharmacokinetic study of evobrutinib and evobrutinib‐diol in dogs after oral administration of evobrutinib at a single dose of 5 mg/kg.     

Determination of salvianolic acid C in rat plasma using liquid chromatography–mass spectrometry and its application to pharmacokinetic study

A sensitive and reliable LC‐ESI‐MS method for the determination of salvianolic acid C in rat plasma has been developed and validated. Plasma samples were prepared by liquid–liquid extraction with ethyl acetate and separated on a Zorbax SB‐C₁₈ column (3.5 µm, 2.1 × 100 mm) at a flow rate of 0.3 mL/min using acetonitrile–water as mobile phase. The detection was carried out by a single quadrupole mass spectrometer with electrospray ionization source and selected ion monitoring mode. Linearity was obtained for salvianolic acid C ranging from 5 to 1000 ng/mL. The intra‐ and inter‐day precisions (RSD, %) didn't exceed 9.96%, and the accuracy (RE, %) were all within ±3.64%. The average recoveries of the analyte and internal standard were >89.13%. Salvianolic acid C was proved to be stable during all sample storage, preparation and analytic procedures. The validated method was successfully applied to pharmacokinetic study after oral and intravenous administration of salvianolic acid C to rats. The absolute oral bioavailability of salvianolic acid C was 0.29 ± 0.05%. This method was further applied to simultaneous determination of salvianolic acid A, salvianolic acid B and salvianolic acid C in rat plasma and showed good practicability. Copyright © 2015 John Wiley & Sons, Ltd.     

A validated LC‐MS/MS method for the determination of senkyunolide I in dog plasma and its application to a pharmacokinetic and bioavailability studies

Senkyunolide I is one of the major bioactive components in the herbal medicine Ligusticum chuanxiong. The aim of this study was to develop and validate a fast, simple and sensitive LC‐MS/MS method for the determination of senkyunolide I in dog plasma. The plasma samples were processed with acetonitrile and separated on a Waters Acquity UPLC BEH C₁₈ column (50 × 2.1 mm, 1.7 μm). The mobile phase consisted of 0.1% formic acid aqueous and acetonitrile was delivered at a flow rate of 0.3 mL min⁻¹. The detection was achieved in the positive selected reaction monitoring mode with precursor‐to‐product transitions at m/z 225.1 → 161.1 for senkyunolide I and at m/z 349.1 → 305.1 for an internal standard. The assay was linear over the tested concentration range, from 0.5 ng mL⁻¹ to 1000 ng mL⁻¹, with a correlation coefficient >0.9992. The mean extraction recovery from dog plasma was within the range of 85.78–93.25%, while the matrix effect of the analyte was within the range of 98.23–108.89%. The intra‐ and inter‐day precisions (RSD) were <12.12% and the accuracy (RR) ranged from 98.89% to 104.24%. The validated assay was successfully applied to pharmacokinetic and bioavailability studies of senkyunolide I in dogs. The results demonstrated that (a) senkyunolide I showed short elimination half‐life (<1 h) in dog, (b) its oral bioavailability was >40% and (c) senkyunolide I showed dose‐independent pharmacokinetic profiles in dog plasma over the dose range of 1–50 mg kg⁻¹.     

HPLC‐ESI‐MS/MS analysis and pharmacokinetics of luteoloside,a potential anticarcinogenic component isolated from Lonicera japonica,in beagle dogs

Luteoloside is a potential anticarcinogenic component isolated from Lonicera japonica, a traditional Chinese medicine (TCM). This study details the development and validation of a sensitive and accurate HPLC‐ESI‐MS/MS method for the quantification of luteoloside in dog plasma. Sample pretreatment includes simple protein precipitation using methanol–acetonitrile (1:1, v/v). A Phenomenex Gemini C₁₈ column (2.0 × 50 mm, i.d., 3.5 µm) was used to separate luteoloside and internal standard by gradient mode with mobile phase consisting of water containing 0.1% formic acid and methanol containing 0.1% formic acid at a flow rate of 0.40 mL/min with a column temperature of 25°C. The detection was performed by positive ion electrospray ionization (ESI) in multiple reaction monitoring mode. The calibration curves were linear (R > 0.995) over the concentration range 1.0–2000 ng/mL and the lower limit of quantification was 1.0 ng/mL. The intra‐day and inter‐day precisions (RSD) were all <15%, accuracies (RE) were within the range of ±15%, and recoveries were between 85.0 and 115%. The validated HPLC‐ESI‐MS/MS method was successfully applied to determine plasma concentrations of luteoloside after intravenous administration of luteoloside at a dose level of 20 mg/kg. Copyright © 2012 John Wiley & Sons, Ltd.     

Development and validation of a UPLC–MS/MS method for determination of Sarsasapogenin‐AA22 in rat plasma and its application to a pharmacokinetic study

A sarsasapogenin derivative, sarsasapogenin‐AA22 (AA22), with cyclobutylamine at the 3‐hydroxyl position of sarsasapogenin, has great neuroprotective activity in PC12 cells and NO production inhibitory activity in RAW264.7 cell lines. A method was developed to determine AA22 in rat plasma which was further applied to evaluate the pharmacokinetics of AA22 after taking a single dose of AA22. Liquid chromatography tandem mass spectrometry was used in the method, while diosgenin was used as internal standard. A simple protein precipitation based on acetonitrile was utilized. A simple sample cleanup promoted the throughput of the method considerably. The method was validated over the range of 1–1000 ng/mL with a correlation coefficient > 0.99. The lower limit of quantification was 1 ng/mL for AA22 in plasma. Intra‐ and inter‐day accuracies for AA22 were 92–111 and 100–103%, respectively, and the inter‐day precision was <15%. After a single oral dose of 25 mg/kg of AA22, the mean peak plasma concentration of AA22 was 2114 ± 362 ng/mL at 6 h. The area under the plasma concentration–time curve was 196,098 ± 69,375 h ng/mL, and the elimination half‐life was 8.7 ± 2.2 h.     

Simultaneous determination of sunitinib and its two metabolites in plasma of Chinese patients with metastatic renal cell carcinoma by liquid chromatography–tandem mass spectrometry

A simple and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for the simultaneous determination of sunitinib and its two metabolites in plasma of Chinese patients with metastatic renal cell carcinoma (mRCC). After simple one‐step protein precipitation with methanol–acetonitrile (1:1, v/v), all three analytes were separated on an Agilent Zorbax SB‐C₁₈ column using a gradient mobile phase consisting of water (0.1% formic acid)–acetonitrile (0.1% formic acid) at a flow rate of 0.50 mL/min. The detection was performed in multiple reaction monitoring mode, using the transitions of m/z 399.0 → 326.2, m/z 371.0 → 283.1, m/z 343.0 → 283.1 and m/z 386.3 → 122.2 for sunitinib, M1, M2 and buspirone, respectively. The method was linear over the range of 0.10–100 ng/mL for all three analytes using only 50 μL of plasma and the lower limit of quantifications for the three analytes were all 0.10 ng/mL. The intra‐day and inter‐day precisions were all less than 15% and the accuracies were within the range of ±15%; recoveries were between 85.0 and 115%. The validated method was successfully applied to an explorative pharmacokinetic study of sunitinib in Chinese patients with mRCC following multi‐dose oral administration. Copyright © 2012 John Wiley & Sons, Ltd.     

The effect of naringenin on the pharmacokinetics of ibrutinib in rat: A drug–drug interaction study

The aim of this study was to investigate the effect of naringenin on the pharmacokinetics of ibrutinib in rats. A simple and sensitive quantitation method based on ultra‐high‐performance liquid chromatography–Q‐Exactive Orbitrap tandem mass spectrometry was developed and validated for the determination of ibrutinib in rat plasma. The samples were extracted using ethyl acetate containing 1% triethylamine and separated on a Waters Acquity UPLC BEH C₁₈ column with acetonitrile and water containing 0.1% formic acid as mobile phase. The assay showed good linearity over the concentration range of 1–1000 ng/mL with coefficient of correlation >0.995. The LLOQ was 1 ng/mL. The assay showed acceptable precision (RSD < 8.65%), accuracy (RE within ±15%), extraction recovery (>78.25%) and negligible matrix effects. The validated method has been successfully applied to the pharmacokinetic study of ibrutinib in rats after oral administration of ibrutinib with or without coadministration of naringenin. Our results demonstrated that naringenin could significantly affect the pharmacokinetics of ibrutinib, including prolonging its half‐life, increase the area under the concentration–time curve and reducing its clearance time. This study indicated that there is potential for drug–drug interactions between naringenin and ibrutinib, and coadministration of ibrutinib with naringenin or naringenin‐containing herbal medicines should be avoided in the clinic.     

Simultaneous determination of l‐tetrahydropalmatine and its active metabolites in rat plasma by a sensitive ultra‐high‐performance liquid chromatography with tandem mass spectrometry method and its application in a pharmacokinetic study

A sensitive and reliable ultra‐high‐performance liquid chromatography with tandem mass spectrometry (UHPLC–MS/MS) method was developed and validated for simultaneous determination of l ‐tetrahydropalmatine (l ‐THP) and its active metabolites l ‐isocorypalmine (l ‐ICP) and L ‐corydalmine (l ‐CD) in rat plasma. The analytes were extracted by liquid–liquid extraction and separated on a Bonshell ASB C₁₈ column (2.1 × 100 mm; 2.7 μm; Agela) using acetonitrile–formic acid aqueous as mobile phase at a flow rate of 0.2 mL/min in gradient mode. The method was validated over the concentration range of 4.00–2500 ng/mL for l ‐THP, 0.400–250 ng/mL for l ‐ICP and 1.00–625 ng/mL for l ‐CD. Intra‐ and inter‐day accuracy and precision were within the acceptable limits of <15% at all concentrations. Correlation coefficients (r ) for the calibration curves were >0.99 for all analytes. The quantitative method was successfully applied for simultaneous determination of l ‐THP and its active metabolites in a pharmacokinetic study after oral administration with l ‐THP at a dose of 15 mg/kg to rats.     

Simultaneous determination of erlotinib and its isomeric major metabolites in human plasma using isocratic liquid chromatography–tandem mass spectrometry and its clinical application

This study developed a method for the simultaneous determination of erlotinib and its isomeric major metabolites, OSI‐413 and OSI‐420, in human plasma using an isocratic liquid chromatography–tandem mass spectrometry. Plasma specimens deproteinized with acetonitrile were separated using a 3‐µm particle size octadecylsilyl column. The m/z values of the precursor and product ions for the analytes were as follows: erlotinib, 394.2/278.2; and OSI‐413 and OSI‐420, 380.2/278.2. The total run time was 21 min and no peaks interfering with the analytes and internal standard (d₆‐erlotinib) in human plasma were observed. The calibration curves of erlotinib, OSI‐413 and OSI‐420 were linear over the concentration ranges of 10–3000, 2–500 and 2–100 ng/mL, respectively. The pretreatment recovery ratios were >86.1%. The intra‐ and inter‐assay precisions and accuracies were <12.7 and 89.0–108.9% for all analytes. This validated method was applied to the determination of plasma samples in lung cancer patients receiving 150 mg of oral erlotinib. The plasma concentration ranges of erlotinib, OSI‐413 and OSI‐420 were 373–2354, 15.7–379 and 2.5–43.6 ng/mL, respectively. In conclusion, the present method can be helpful for evaluating the plasma exposures of erlotinib and its major isomeric metabolites in clinical settings. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous determination of neochlorogenic acid,chlorogenic acid,cryptochlorogenic acid and geniposide in rat plasma by UPLC‐MS/MS and its application to a pharmacokinetic study after administration of Reduning injection

A simple, specific and sensitive ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was established and validated for simultaneous determination of neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid and geniposide in rat plasma using puerarin as an internal standard (IS). Plasma samples were pretreated by a one‐step direct protein precipitation procedure with acetonitrile after acidified using as little as 50 μL plasma. Chromatographic separation was performed on an Acquity BEH C₁₈ column (100 × 2.1 mm, 1.7 µm) at a flow rate of 0.2 mL/min by a gradient elution, using 0.2% acetic acid–methanol as mobile phase. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring via electrospray ionization source with negative ion mode. Calibration curves showed good linearity (r > 0.995) over wide concentration ranges. The intra‐ and inter‐day precisions were <15%, and the accuracy was within ±8.0%. The validated method was successfully applied to a pharmacokinetic study of the four bioactive components in rats after intravenous administration of Reduning injection. Copyright © 2014 John Wiley & Sons, Ltd.     

LC‐ESI‐MS/MS analysis of quercetin in rat plasma after oral administration of biodegradable nanoparticles

A simple, rapid and sensitive LC‐MS/MS method was developed and validated for the determination of free quercetin in rat plasma, using fisetin as internal standard. The detection was performed by negative ion electrospray ionization under selected reaction monitoring. Chromatographic separation (isocratic elution) was carried out using acetonitrile–10 m m ammonium formate (80:20, v/v) with 0.1% v/v formic acid. The lower limit of quantification (4.928 ng/mL) provided high sensitivity for the detection of quercetin in rat plasma. The linearity range was from 5 to 2000 ng/mL. Intra‐ and inter‐day variability (RSD) of quercetin extraction from rat plasma was <4.19 and 1.37% with accuracies of 98.77 and 99.67%. The method developed was successfully applied for estimating free quercetin in rat plasma, after oral administration of quercetin‐loaded biodegradable nanoparticles (QLN) and quercetin suspension. QLN (C_max, 1277.34 ± 216.67 ng/mL; AUC, 17,458.25 ± 3152.95 ng hr/mL) showed a 5.38‐fold increase in relative bioavailability as compared with quercetin suspension (C_max, 369.2 ± 108.07 ng/mL; AUC, 3276.92 ± 396.67 ng hr/mL). Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous quantitation of polygalaxanthone III and four ginsenosides by ultra‐fast liquid chromatography with tandem mass spectrometry in rat and beagle dog plasma after oral administration of Kai‐Xin‐San: Application to a comparative pharmacokinetic study

A fast, selective, and quantitative ultra‐fast liquid chromatography with tandem mass spectrometry method has been developed and validated for the simultaneous quantitation of polygalaxanthone III, ginsenoside Rb1, ginsenoside Rd, ginsenoside Re, and ginsenoside Rg1 in the plasma of rat and beagle dog after oral administration of Kai‐Xin‐San. After addition of the internal standard, salidroside, the plasma samples were extracted by liquid–liquid extraction and separated on a Venusil MP C₁₈ column with methanol/0.01% acetic acid water as mobile phase. The tandem mass spectrometric detection was performed in the multiple reaction monitoring with turbo ion spray source in a switching ionization mode. The method was examined, and found to be precise and accurate with the linearity range of the compounds. The intra‐ and interday precision and accuracy of the analytes were well within acceptance criteria (±15%). The mean extraction recoveries of analytes and internal standard were all >75.0%. The validated method has been successfully applied to comparing pharmacokinetic profiles of analytes in rat and beagle dog plasma. The results indicated that no significant differences were observed in pharmacokinetic parameters of ginsenoside Rg1, while the others had significant differences, which may due to the different mechanisms of absorption and metabolism.     

Pharmacokinetics and metabolism of ulixertinib in rat by liquid chromatography combined with electrospray ionization tandem mass spectrometry

The purpose of this study was to develop and validate a simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of ulixertinib in rat plasma. The plasma samples were precipitated with acetonitrile and then separated on a C₁₈ column with water containing 0.1% formic acid and acetonitrile as mobile phase at a flow rate of 0.3 mL/min. Analytes were monitored on a TSQ Vantage triple quadrupole tandem mass spectrometer operated in positive electrospray ionization mode. Selected reaction monitoring transitions were m/z 433.1→262.1 for ulixertinib and m/z 450.1→260.1 for internal standard. The assay achieved good linearity over the concentration range of 0.1‐1000 ng/mL with correlation coefficient > 0.9991. The validated assay has been successfully applied to pharmacokinetic study of ulixertinib in rat after oral and intravenous administration. The results revealed that ulixertinib showed high exposure in rat plasma, low clearance, moderate oral bioavailability (45.13%), and dose‐independent pharmacokinetic profiles over the oral dose range of 1‐15 mg/kg. In addition, six metabolites from rat plasma and hepatocytes were detected and structurally identified by ultra‐high performance liquid chromatography combined with high‐resolution mass spectrometry. The metabolic pathways of ulixertinib referred to hydroxylation and dealkylation and glucuronidation.     

Simultaneous quantitative analyses of indole and oxindole alkaloids of Uncaria Hook in rat plasma and brain after oral administration of the traditional Japanese medicine Yokukansan using high‐performance liquid chromatography with tandem mass spectrometry

Uncaria Hook (UH) alkaloids are involved in the beneficial effects of Yokukansan. However, the pharmacokinetics of UH alkaloids after oral administration of Yokukansan has not yet been sufficiently investigated. Therefore, we developed and validated a sensitive and specific high‐performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) method for the simultaneous quantitation of seven UH alkaloids (corynoxeine, isocorynoxeine, rhynchophylline, isorhynchophylline, hirsutine, hirsuteine and geissoschizine methyl ether) in rat plasma and brain. After protein precipitation with acetonitrile, chromatographic separation was performed using an Ascentis Express RP‐amide column, with gradient elution with 0.2% formic acid and acetonitrile at 0.3 mL/min. All analytes in the plasma and brain showed good linearity over a wide concentration range (r > 0.995). Intra‐day and inter‐day variations of each constituent were 8.6 and 8.0% or less in the plasma, and 14.9 and 15.0% or less in the brain, respectively. The validated LC/MS/MS method was applied in the pharmacokinetic studies of UH alkaloids after oral administration of Yokukansan to rats. In the plasma, rhynchophylline, hirsutine, hirsuteine and geissoschizine methyl ether were detected, but only geissoschizine methyl ether was detected in the brain. These results suggest that geissoschizine methyl ether is an important constituent of the pharmacological effects of Yokukansan. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous determination of praziquantel,pyrantel embonate,febantel and its active metabolites,oxfendazole and fenbendazole,in dog plasma by liquid chromatography/mass spectrometry

A liquid chromatography–electrospray–mass spectrometry method (LC/MS) has been developed and validated for determination of praziquantel (PZQ), pyrantel (PYR), febantel (FBT), and the active metabolites fenbendazole (FEN) and oxfendazole (OXF), in dog plasma, using mebendazole as internal standard (IS). The method consists of solid‐phase extractions on Strata‐X polymeric cartridges. Chromatographic separation was carried out on a Phenomenex Gemini C₆‐Phenyl column using binary gradient elution containing methanol and 50 mm ammonium–formate (pH 3). The method was linear (r² ≥ 0.990) over concentration ranges of 3–250 ng/mL for PYR andFEB, 5–250 ng/mL for OXF and FEN, and 24–1000 ng/mL for PZQ. The mean precisions were 1.3–10.6% (within‐run) and 2.5–9.1% (between‐run), and mean accuracies were 90.7–109.4% (within‐run) and 91.6–108.2% (between‐run). The relative standard deviations (RSD) were <9.1%. The mean recoveries of five targeted compounds from dog plasma ranged from 77 to 94%.The new LC/MS method described herein was fully validated and successfully applied to the bioequivalence studies of different anthelmintic formulations such as tablets containing PZQ, PYR embonate and FBT in dogs after oral administration. Copyright © 2015 John Wiley & Sons, Ltd.