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Lumateperone is a novel agent approved by FDA for treatment of schizophrenia in adults. To elucidate the species differences in the of biotransformation of lumateperone and its pharmacokinetic (PK) characteristics in rats, the metabolite identification of lumateperone was carried out in rat, dog and human liver microsomes, and rat plasma after oral administration using UPLC-Q Exactive Orbitrap high-resolution mass spectrometry HRMS. Furtherly, the PK characteristics of lumateperone and its N-demethylated metabolite (M3) in rat plasma were investigated using a validated LC-MS/MS method following intravenous and oral administration. Fourteen phase I metabolites were found in liver microsomes and ten of them were observed in rat plasma. N-demethylation, carbonylation, dehydrogenation, and piperazine ring cleavage were main metabolic pathway of lumateperone. No unique metabolites were formed in human liver microsomes. After rapid absorption in rats, lumateperone was quickly metabolized and eliminated with bioavailability of less than 5%. The exposure level of M3 was about 1.5-fold higher than that of lumateperone in rat plasma. Lumatperone underwent extensive metabolism and was absorbed rapidly in rats. Metabolite M3 had equivalent or slightly higher exposure levels than lumateperone. This study provides essential PK information to facilitate further pharmacodynamic researches of lumateperone., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Within the family of serotonin (5-HT) receptors, the 5-HT 1A subtype is particularly interesting as it may be involved in various physiological processes or psychological disorders. The p-[ 18 F]MPPF, a highly selective 5-HT 1A antagonist, is used for in vivo studies in human or animal by means of positron emission tomography (PET) [1]. In order to selectively extract p-[ 18 F]MPPF and its main metabolites from plasma, molecularly imprinted polymer (MIP) was prepared against these compounds by using the p-MPPF as template. For the control of the selectivity, non-imprinted polymer (NIP) was also synthesized without template. The MIP sorbent, packed in disposable extraction cartridges (DECs), was then evaluated as molecularly imprinted solid-phase extraction (MISPE) prior to the LC determination. The conditions of extraction were evaluated in order to obtain the highest selective retention of the p-[ 18 F]MPPF and its metabolites on this MIP. The MIP selectivity was exploited in the loading and washing steps by adjusting the pH of plasma samples at a suitable value and by selecting mixtures for the washing step to limit the contribution of non-specific interactions. Other important parameters involved in the conditioning and elution steps were also studied. Finally, a pre-validation was carried out with optimal extraction conditions to demonstrate the performance of this MISPE-LC method as a generic method in the context of evaluation of new MISPE for p-[ 18 F]MPPF and its potential for metabolites extraction from human plasma., Competing Interests: Declaration of Competing Interest Not applicable, (Copyright © 2019 Elsevier B.V. All rights reserved.)

A new method for the quantitative analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) of five tyrosine kinase inhibitors (afatinib, crizotinib, osimertinib, erlotinib and nintedanib) used in the treatment of non-small cell lung cancer (NSCLC) was developed and validated in human plasma. Separation was performed on an Accucore ® C18 (2.1 × 50 mm; 2.6 μm) column using a gradient elution of water acidified with 0.1% (v/v) formic acid (A) and acetonitrile containing 0.1% (v/v) formic acid (B) at a flow rate of 500 μL/min. The analytes were detected in the selected reaction monitoring mode of a triple quadrupole mass spectrometer after positive ionization with heated electrospray interface. After addition of three isotopically labeled internal standards, plasma pretreatment consisted in a simple protein precipitation. This method presented satisfactory results in terms of sensitivity, specificity, precision (intra- and inter-assay coefficient of variation from 2.6% to 10.6%), accuracy (from 96.1% to 108.5%), recovery and matrix effects. The lower limit of quantification and the linearity of these five tyrosine kinases inhibitors are suitable with the expected concentrations in clinical practice. This new bioanalytical method can be used in daily clinical practice for therapeutic drug monitoring of these tyrosine kinase inhibitors in NSCLC patients., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of aripiprazole and its active metabolite, dehydro-aripiprazole, in human plasma. Stable isotopically labeled aripiprazole, aripiprazole-D8, has been used as the internal standard (IS) for both analytes. Only 200 μl of human plasma was needed for analyte extraction, using effective phospholipids-eliminating three-step microelution-solid-phase extraction (SPE, Oasis PRiME HLB 96-well μElution Plate). An ACE C18-PFP column was applied for chromatographic separation at 25 °C, protected by a 0.2-μm on-line filter. A combination of ammonium formate (5 mM)-acetonitrile (pH 4.0; 65:35, v/v) was used as mobile phase and the chromatogram was run under gradient conditions at a flow rate of 0.6 ml/min. Run time lasted 5 min, followed by a re-equilibration time of 3 min, to give a total run time of 8 min. Five μl of the sample was injected into the chromatographic system. Aripiprazole, dehydro-aripiprazole and IS were detected using the mode multiple reaction monitoring in the positive ionization mode. The method was linear in the concentration range of 0.18-110 ng/ml and 0.35-100 ng/ml for aripiprazole and dehydro-aripiprazole, respectively. Our method has been validated according to the recommendations of regulatory agencies through tests of precision, accuracy, recovery, matrix effect, stability, sensitivity, selectivity and carry-over. Our microelution-SPE method removes more than 99% of main plasma phospholipids compared to protein precipitation and was successfully applied to several bioequivalence studies., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An ultra high-performance liquid chromatographic (UHPLC) method with PDA detection was developed and validated for the simultaneous quantification of metronidazole, meropenem, ciprofloxacin, linezolid and piperacillin in human plasma and applied to patients suffering from hospital acquired pneumonia (HAP). The method uses an air assisted dispersive liquid-liquid microextraction for sample preparation. All parameters in the extraction step, including selection of extractant, amount of extractant, ionic strength, pH, and extraction cycles, were investigated and optimized. Chromatography was carried out using a Poroshell 120 SB C 18 (50 × 2.1 mm I.D. 2.6 μm particle size) column and a gradient mobile phase consisting of ammonium acetate buffer (10 mM, pH 4.0) (eluent A); and a mixture of acetonitrile-methanol in a ratio (80/20)(eluent B). Ulifloxacin was used as internal standard. The method demonstrated good linearity with correlation coefficients, r 2  > 0.9995 for the drugs, as well as high precision (RSD% ≤ 9.87%), accuracy ranged from -8.14% to +8.98. The enrichment factor (EF) obtained ranged within 87 and 121. During the validation, the concentrations of the analytes were found to be stable after 3 freeze-thaw cycles and for at least 24 h after extraction. Subsequently, this method was used to quantify the drugs in patients with HAP in order to establish if the dosage regimen given was sufficient to eradicate the infection at the target site., (Copyright © 2017. Published by Elsevier B.V.)

To establish a rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of vortioxetine, carvedilol and its metabolite 4-hydroxyphenyl carvedilol in rat plasma. The analytes and the internal standard (diazepam) were separated on an Acquity UPLC BEH C18 chromatography column (2.1mm×50mm, 1.7μm) using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water at a flow rate of 0.4mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 299.2→150.1 for vortioxetine, m/z 407.2→100.3 for carvedilol, m/z 423.2→100.1 for 4-hydroxyphenyl carvedilol and m/z 285.2→193.1 for diazepam (IS) using a positive electrospray ionization interface. The method was validated over a concentration range of 0.5-100ng/mL for vortioxetine, 0.5-1000ng/mL for carvedilol and 0.1-50ng/mL for 4-hydroxyphenyl carvedilol. Total time for each chromatograph was 3.0min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD)<11.6% and the accuracy values ranged from -12.2% to 11.3%. The analytical method was successfully applied to a pharmacokinetic interaction study of vortioxetine and carvedilol after oral administration vortioxetine and carvedilol in rats. Results suggested that the co-administration of vortioxetine and carvedilol results in a significant drug interaction in rats., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A procedure based on solid-phase extraction (SPE) followed by high performance liquid chromatography (HPLC) with PDA detection has been developed for the analysis of multiple drugs in rat plasma. The analytes evaluated were ulifloxacin, fenbufen and felbinac. Eight different solid phase extraction cartridges were tested to evaluate their applicability for the isolation of drugs from rat plasma. Comparison were recovery of different drugs and reproducibility. The samples were analyzed by HPLC using a Kinetex C18 EVO column and acetonitrile-10mM ammonium acetate-methanol as the mobile phase under gradient elution conditions. SPE combined with HPLC-PDA allowed the determination of drugs over a linear range of 0.05-15 μg/mL for ulifloxacin while 0.5-50 μg/mL for felbinac and fenbufen, with limit of detection at 0.05 for ulifloxacin and 0.5 for felbinac and fenbufen. Bond Elut Plexa sorbent was found to provide the most effective clean-up, removing the greatest amount of interfering substance and simultaneously ensuring analyte recoveries higher than 93.54% with relative standard deviation (RSD) <10%. The method was applied with good accuracy and precision in the determination of ulifloxacin, fenbufen and felbinac in rat plasma obtained from rats treated with selected drugs. This method permits its application to pharmacokinetic and pharmacodynamic studies of these analytes and will facilitate detailed investigations on the interactions between new fluoroquinolones and fenbufen., (Copyright © 2016. Published by Elsevier B.V.)

A rapid and sensitive LC-MS/MS method was developed for the quantification of vilazodone in rat plasma using escitalopram as internal standard. After extracted with organic solvent, post-treatment samples were chromatographed on an Agela C18 column. An isocratic mobile phase of acetonitrile: 5mM ammonium acetate: formic acid (35:65:0.1, v/v/v) was applied at a flow rate of 0.25mL/min. Detection was performed using multiple reaction-monitoring (MRM) modes at m/z 442.4→155.3 for vilazodone and m/z 325.1→109.0 for escitalopram. The method was linear in the concentration range of 1.0-100ng/mL with a correlation coefficient ≥0.993. The intra- and inter-assay precision (%RSD) values were within 13.4%, and intra- and inter-day accuracy (%RE) ranged from -9.8 to 6.9%. The total analysis time was 2.2min. The LC-MS/MS method was fully validated for its sensitivity, selectivity, stability, matrix effect and recovery. The data indicated that the developed method was rapid, specific and sensitive. This method was further and successfully applied in the pharmacokinetics study of vilazodone in rat., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A simultaneous, selective, sensitive, and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of bosentan, ambrisentan, sildenafil, and tadalafil in 50μL of human blood plasma. Diluted plasma samples were extracted using a solid-phase extraction procedure with 2% formic acid and methanol. The four drugs were separated by high-performance liquid chromatography using a C18 column and an isocratic mobile phase running at a flow rate of 0.2mL/min for 5min. The drugs were detected by a tandem mass spectrometer with electrospray ionization using deuterated compounds as internal standards. Calibration curves were generated over the linear concentration range of 2-1000ng/mL in plasma with a lower limit of quantification of 2ng/mL for all compounds. Finally, this validated method was applied to a clinical pharmacokinetic study in pediatric patients with pulmonary arterial hypertension (PAH) following the oral administration of PAH drugs. These results indicate that this method is suitable for assessing the risk/benefit of combination therapy in the pediatric population and useful for therapeutic drug monitoring for PAH treatment., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This work proposes a liquid chromatography-electrospray ionization ion trap mass spectrometry (LC-ESI-ITMS) method, for the quantification of sildenafil (SDF), tadalafil (TDF) and vardenafil (VDF) and their metabolites N-desmethylSDF, O-desethylSDF and N-desethylVDF, preceded by a sample preparation step based on protein and phospholipid elimination. A C8 column (150 mm × 4.6 mm, 5 μm) with ammonium formate (20mM) and acetonitrile as the mobile phase components have been used. This method has been validated, obtaining limits of quantification ranged from 1 to 2.5 ng/mL and 2 to 5 ng/g in serum and brain tissue respectively, while limits of detection ranged from 0.3 to 0.9 ng/mL in serum and 0.6 to 1.9 ng/g in brain tissue. Assay recoveries for low level QC samples were higher than 83% and the matrix effect ranged between 91% and 108% in serum and between 98% and 107% in brain tissue. The method has been applied to the quantification of these compounds in the serum and brain tissue of rats treated intraperitoneally with 10 mg/kg of SDF, TDF or VDF., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background and Objectives: Current liquid chromatographic tandem mass spectrometry (LC-MS/MS) methods to measure serum levels of aripiprazole (Ar) and dehydroaripiprazole (DHAr) are sensitive, but difficult to use in a hospital context. We aimed to develop a rapid LC-MS/MS method allowing reliable level measurement in the presence of co-administered drugs, withdrawing samples from 22 patients with acute agitation receiving 9.75 mg aripiprazole IM injection., Method: We developed a sensitive and selective HPLC-MS/MS method to measure serum Ar and DHAr levels in a hospital laboratory, requiring minimal sample preparation and inferior sample volume compared to previous LC-MS/MS methods. Analytes were separated on a reversed-phase HPLC (run-time, 10 min). A triple quadrupole tandem mass spectrometer was used for quantitative analysis in positive mode by a multiple reaction monitoring. Samples were drawn 2, 4, 6, and 24h post-injection., Results: Calibration curves (2-1000 ng/mL for Ar and 3.5-500 ng/mL for DHAr) were linear, with mean correlation coefficient >0.9998. Within- and between-day precision and accuracy were within 10%. Mean recovery was 95.2 ± 4.5% for Ar and 97.6 ± 7.2% for DHAr. Ar and DHAr peaks were not affected by other co-administered psychotropic drugs., Conclusion: Our method measured Ar and DHAr concentrations reliably, simply and rapidly without employing many reagents, as currently existing methods., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A new method using high performance liquid chromatography coupled with electrospray mass spectrometry is described for the quantification of PBMC concentration of tyrosine kinase inhibitors imatinib, dasatinib and nilotinib. A simple PBMC isolation and extraction procedure were applied on 10-14 mL of blood aliquots. Chromatographic separation of drugs and Internal Standard (quinoxaline) was achieved with a gradient (acetonitrile and water+formic acid 0.05%) on a C18 reverse phase analytical column with 25 min of analytical run, at flow rate of 0.25 mL/min. Mean intra- and inter-day precision for all compounds were 8.76 and 12.20%; mean accuracy was -3.86%; extraction recovery ranged within 79 and 91%. Calibration curves ranged from 50.0 to 0.25 ng. The limit of quantification was set at 0.25 ng for all the analyzed drugs. This novel developed methodology allows a specific, sensitive and reliable simultaneous intracellular determination of the three tyrosine kinase inhibitors imatinib, dasatinib and nilotinib in a single chromatographic run, useful for drugs estimation in PBMC of patients affected by chronic myeloid leukemia., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A novel T-type calcium channel blocker, 4-amino-1-{4-[(4-chloro-phenyl)-phenyl-methyl]-piperazin-1-yl}-butan-1-one (HYP-10) has been synthesized, and the compound has shown promise as both a nociceptive and inflammatory pain reliever as well as an analgesic in a rat neuropathic pain model. A quantification method was developed for the determination of HYP-10 in rat plasma. After simple protein precipitation with methanol, HYP-10 and the internal standard, methaqualone were chromatographed on a reversed-phase column and detected by liquid chromatography/tandem mass spectrometry with electrospray ionization. The accuracy and precision of the assay were in accordance with FDA regulations for validation of bioanalytical methods. This method was applied to measure the plasma HYP-10 concentration after a single intravenous administration of the compound in rats., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Traditional chiral chromatographic separation method development is time consuming even for an experienced chromatographer. This paper describes the application of computer software ACD Lab to facilitate the development of chiral separation for the quantitation of eszopiclone using LC-MS/MS technology. Assisted by ACD/Chrom Manager and LC Simulator software, the optimal chiral chromatographic development was completed within hours. The baseline chiral separation was achieved with a total cycle time of 3 min. For sample extraction method development, a Waters Oasis Sorbent Selection Plate containing four different sorbents was utilized. Optimal conditions were determined using a single plate under various load, wash and elution conditions. This was followed by a GLP validation which demonstrated excellent intra- and inter-day accuracy and precision for the quantitation of eszopiclone in human plasma at 1.00-100 ng/mL range using LC/MS/MS technology. This method was utilized to support multiple clinic bioequivalence studies., (Copyright (c) 2010. Published by Elsevier B.V.)

A sensitive and precise LC-ESI-MS/MS method for determination of nutlin-3a in murine plasma using ketoconazole as an internal standard was developed and validated. Plasma nutlin-3a samples were prepared by either a simple protein precipitation (PP) for the high concentration range (10-20,000ng/mL) or by liquid-liquid extraction (LLE) for the low concentration range (0.25-300ng/mL). Nutlin-3a and ketoconazole were separated on a modified C18 analytical column (4microm, 75mmx2mm) with an isocratic mobile phase (acetonitrile/5mM HCOONH(4)=70/30, v/v). The retention times of nutlin-3a and ketoconazole were 1.14 and 1.45min. Detection was achieved by a tandem MS system, monitoring m/z 582/99 and m/z 532/82 for nutlin-3a and ketoconazole, respectively. The PP method was linear in a range of 10-20,000ng/mL (R(2)>or=0.993) and the LLE method was linear in a range of 0.25-300ng/mL (R(2)>or=0.992). The mean recoveries for PP and LLE were 24% and 78%, respectively. Within-day and between-day precisions were

A sensitive and specific high performance liquid chromatography method with UV detection was developed and validated for the determination of PAC-1 in rat plasma. After extraction with ethyl acetate, the chromatographic separation was carried out on a Diamonsil C(18) column (150mmx4.6mm i.d., 5microm particle size, Zhonghuida) protected by a ODS guard column (10mmx4.6mm i.d., 5microm particle size), using acetonitrile-methanol-phosphate buffer (pH 3.0, 30mM) (31:3:66, v/v/v) as mobile phase at a flow rate of 1.0mL/min, and wavelength of the UV detector was set at 281nm. No interference from any endogenous substances was observed during the elution of PAC-1 and internal standard (IS, indapamide). The calibration curve was linear over the range of 0.05-20microg/mL (r>0.99). The lower limit of quantification was evaluated to be 50ng/mL. The method was successfully applied to the pharmacokinetic study of PAC-1 after intravenous and oral administration in rats, respectively.

The purpose of the present study was to determine sildenafil and a novel PDE-5 inhibitor, mirodenafil in the plasma and corpus cavernosum tissue of rats to compare their pharmacokinetic properties. The concentrations of mirodenafil and sildenafil in the rat plasma and corpus cavernosum tissue samples were analyzed using LC-MS/MS after a single oral administration at a dose of 40mg/kg to rats. Although the T(max), Tlambda(1/2) and MRT were not different between mirodenafil and sildenafil, the C(max) and AUC of mirodenafil were significantly higher than those of sildenafil in the plasma and corpus cavernosum tissue. Consequently mirodenafil remained longer than sildenafil in the plasma and tissue. This may provide pharmacokinetic evidence for assessment of the in vivo efficacy of mirodenafil and sildenafil.

A simple, sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantification of ranolazine in human plasma. The analytical method consists in the precipitation of plasma sample with methanol, followed by the determination of ranolazine by an LC-MS/MS. The analyte was separated on a Peerless Cyano column (33 mm x 4.6 mm, 3 microm) an isocratic mobile phase of methanol-water containing formic acid (1.0%, v/v) (65:35, v/v) at a flow rate of 1.0 ml/min. Protonated ions formed by a turbo ionspray in positive mode were used to detect analyte and internal standard (IS). The MS/MS detection was made by monitoring the fragmentation of m/z 428.20-->279.50 for ranolazine and m/z 448.30-->285.20 for internal standard on a triple quadrupole mass spectrometer. The method was validated over the concentration range of 5-2000 ng/ml for ranolazine in human plasma with correlation coefficient of 0.9937 (S.D.: +/-0.00367, range: 0.9895-0.9963). The accuracy and precision values obtained from six different sets of quality control samples analyzed in separate occasions ranged from 94.53 to 117.86 and 0.14% to 4.56%, respectively. Mean extraction recovery was 82.36-94.25% for three quality control (QC) samples and 88.37% for IS. Plasma samples were stable for three freeze-thaw cycles, or 24h ambient storage, or 1 and 3 months storage at -20 degrees C. Processed samples (ready for injection) were stable up to 72 h at autosampler (4 degrees C). The developed method was successfully applied for analyzing ranolazine in plasma samples for a bioequivalence study with 12 healthy volunteers.

The present paper deals with the development of a rapid and feasible high-performance liquid chromatographic method for the determination of trazodone and its main active metabolite 3-(1-clorophenyl)piperazine (m-CPP) in human plasma. Trazodone is a second-generation antidepressant with serotonin antagonist activity. The metabolite seems to be involved in the onset of some side effects of trazodone therapy, thus its determination is very important during therapeutic drug monitoring. Separation was achieved using a C8 reversed-phase column and a mobile phase composed of aqueous phosphate buffer (70%), containing triethylamine, at pH 3.5 and acetonitrile (30%). The UV detector was set at 255 nm and loxapine was used as the internal standard. An original pre-treatment procedure of plasma samples was developed, based on solid-phase extraction with C8 reversed phase cartridges (50mg, 1 mL). The obtained extraction yields values were higher than 90% and precision, expressed as R.S.D., was lower than 5.6%. The method was successfully applied to plasma samples from depressed patients undergoing therapy with trazodone; accuracy results were satisfactory (recovery >91%). Thus, the method seems to be suitable for the therapeutic drug monitoring of trazodone and its main active metabolite in depressed patients' plasma.

A simple, sensitive and specific liquid chromatography/tandem mass spectrometry method for the quantitation of aildenafil, a new phosphodiesterase V inhibitor, in human plasma is presented. The analyte and internal standard, sildenafil, were extracted by a one-step liquid-liquid extraction in alkaline conditions and separated on a C(18) column using ammonia:10mM ammonium acetate buffer:methanol (0.1:15:85, v/v/v) as the mobile phase. The detection by an API 4000 triple quadrupole mass spectrometer in multiple-reaction monitoring mode was completed within 2.5 min. The calibration curve exhibited a linear dynamic range of 0.05-100 ng/ml with a 10 pg/ml limit of detection. The intra- and inter-day precisions measured as relative standard deviation were within 8.04% and 5.72%, respectively. This method has been used in a pharmacokinetic study of aildenafil in healthy male volunteers each given an oral administration of one of the three dosages.

A rapid, selective and sensitive high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) method coupled with high flow direct-injection on-line extraction has been developed and validated for the simultaneous quantitation of nefazodone and its three active metabolites, hydroxynefazodone, triazole-dione (BMS-180492) and m-chlorophyenylpiperazine (mCPP) in human plasma. The method utilized d7-nefazodone, d7-hydroxynefazodone, d4-BMS-180492 and d4-mCPP as internal standards (IS). The plasma samples were injected into the LC-MS/MS system after simply adding the internal standard solution and centrifuging. The required extraction and chromatographic separation of the analytes were achieved on an Oasis HLB column (on-line extraction column, 1 mm x 50 mm, 30 microm) and a conventional Luna C8 column (analytical column, 4.6 mm x 50 mm, 5 microm). Detection was by positive ion electrospray tandem mass spectrometry. The total analysis run time for each sample was 2 min, which included the time needed for on-line extraction, chromatographic separation and LC-MS/MS analysis. The assay was validated for each analyte and the concentrations ranged from 2.0 to 500 ng/ml for nefazodone, hydroxynefazodone and mCPP and from 4.0 to 1000 ng/ml for BMS-180492, respectively. The assay was used for the high-throughput sample analysis of thousands of pharmacokinetic study samples and was proven to be rapid, accurate, precise, sensitive, specific and rugged.

A simple and sensitive LC-MS/MS analytical method was developed and validated for the determination of LASSBio-579 in plasma rat, using fluconazole as internal standard. Analyses were performed on a Shimadzu HPLC system using a Shimadzu C18 column and isocratic elution with acetonitrile-water (80:20, v/v), containing 0.4mM ammonium hydroxide and 0.2 mM acetic acid at a flow rate of 1.0 ml/min (split ratio 1:5). A Micromass triple quadrupole mass spectrometer, equipped with an electrospray ionization interface, operated in the positive mode. Plasma samples were deproteinized with acetonitrile (1:2) and 50 microl of the supernatant were injected into the system. The retention times of LASSBio-579 and IS were approximately 4.7 and 2.4 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 30-2000 ng/ml with determination coefficient >0.98. The lower limit of quantification was 30 ng/ml. The accuracy of method was within 15%. Intra- and inter-day relative standard deviations were less or equal to 13.5% and 6.4%, respectively. The applicability of the LC-MS/MS method for pharmacokinetic studies was tested using plasma samples obtained after intraperitoneal administration of LASSBio-579 to male Wistar rats. No interference from endogenous substances was observed, showing the specificity of the method developed. The reported method can provide the necessary sensitivity, linearity, precision, accuracy, and specificity to allow the determination of LASSBio-579 in pre-clinical pharmacokinetic studies.

A method which employed high-performance liquid chromatography coupled with electrochemical detection was developed for the simultaneous determination of sildenafil and its metabolite, N-desmethyl sildenafil, in human plasma has. The method was developed and validated for purposes of its application to a pharmacokinetic study in healthy volunteers after an oral dose of 50mg/tablet under fasting conditions. High precision and accuracy were demonstrated. A one-step liquid-liquid extraction further provides a simple and practical way to process plasma samples containing sildenafil with good quantitative recovery. Sampling lasted for 24h after dosing; consequently a limit of quantitation (LOQ) of 7.858 ng/mL was achieved for sildenafil whereas a LOQ of 8.675 ng/mL was obtained for N-desmethyl sildenafil. The mobile phase consisted of acetonitrile, methanol and phosphate buffer (0.05 M) (18.5:34.5:47.0, v/v/v) pH 7.68. The stationary phase was a C(8) (150 mm x 4.6 mm), 5 microm particle size operated at 27 degrees C. All analytes were stable at the pH of the supernatant, and during the analytical time window. At the applied potential of +1.20 V versus Ag/AgCl, no interferences from endogenous plasma compounds were recorded at the retention times of sildenafil, N-desmethyl sildenafil. High resolution was obtained between the analytes and the employed internal standards.

HPLC method for the determination of sildenafil and its metabolite (N-demethylsildenafil) in rat serum has been developed. The technique included a solid phase extraction of the serum samples on a [poly(divinylbenzene-co-N-vinylpyrrolidone)] solid phase extraction sorbent. After conditioning, the cartridge was loaded with 0.5 mL of buffered serum containing internal standard. Elution was made with 1 mL of acetonitrile. After evaporation of the eluates to dryness and reconstitution with methanol, the samples were analyzed on Kromasil C18 column phase with phosphate buffer 0.05 M/acetonitrile: 54/46, pH 8. Detection was carried out using a photodiode array detector. For sildenafil and demethylsildenafil, full validation of the proposed method was provided (linearity range, calibration curves, average extraction efficiency; average intra-day and interday variabilities, limit of detection, limit of quantification, specificity). The proposed method was successfully utilised to quantify sildenafil and N-demethylsidenafil in rat serum for a pharmacokinetic study.

A rapid, simple and accurate high performance liquid chromatography (HPLC) method was developed and validated for the determination of LASSBio-581 (1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-phenyl-piperazine) in rat plasma using ketoconazole as internal standard. Plasma samples were deproteinized with methanol. A good chromatographic separation was achieved using a reversed phase C18 column. Mobile phase consisting of sodium dihydrogen phosphate monohydrate (pH 4.5, 0.02 M) and methanol mixture (35:65, v/v) was used at a flow rate of 1.0 ml/min. The eluate was monitored using a UV detector at 248 nm. The retention times of LASSBio-581 and the internal standard were approximately 3.8 and 5.6 min, respectively. The calibration curves were linear over the concentration range of 0.25-8.0 microg/ml with correlation coefficients >0.99. The limit of quantitation was 0.25 microg/ml. The accuracy of the method was >90%. The intra-day relative standard deviation (R.S.D.) ranged from 6.15 to 10.52% at 0.4 microg/ml, 7.44 to 13.81% at 1.5 microg/ml and 6.10 to 13.94% at 6.0 microg/ml. The inter-day R.S.D. were 9.54, 8.42 and 8.25% at 0.4, 1.5 and 6.0 microg/ml, respectively. No interference from endogenous substances or metabolites were observed. The method has been used to measure plasma concentrations of LASSBio-581 in pharmacokinetic studies in rats.

A liquid chromatography-tandem mass spectrometric method for the simultaneous determination of sildenafil and its active N-demethylated metabolite, UK-103,320 in human plasma was developed. Sildenafil, UK-103,320 and the internal standard (DA-8159) were extracted from human plasma with dichloromethane at basic pH. A reverse-phase LC separation was performed on Luna phenylhexyl column with the mixture of acetonitrile-ammonium formate (10 mM, pH 6.0) (60:40, v/v) as mobile phase. The detection of analytes was performed using an electrospray ionization tandem mass spectrometry in the multiple reaction-monitoring mode. The lower limits of quantification for sildenafil and UK-103,320 were 2.0 ng/ml. The method showed a satisfactory sensitivity, precision, accuracy, recovery and selectivity.

Signal Transduction Inhibitor 571 (STI571, formerly known as CGP 57148B) or Gleevec received fast track approval by the US Food and Drug Administration (FDA) for treatment of chronic myeloid leukemia (CML). STI571 (Gleevec) is a revolutionary and promising new oral therapy for CML, which functions at the molecular level with high specificity. The dramatic improvement in efficacy compared with existing treatments prompted an equally profound increase in the pace of development of Gleevec. The duration from first dose in man to completion of the New Drug Application (NDA) filing was less than 3 years. In addition, recently, FDA approved Gleevec for the treatment of gastrointestinal stromal tumor (GIST). In order to support all toxicokinetic (TK) studies with sufficient speed to meet various target dates, a semi-automated procedure using solid phase extraction (SPE) was developed and validated. A Packard Multi-Probe I and a SPE step in a 96-well plate format were utilized. A 3M Empore octyl (C(8))-standard density 96-well plate was used for plasma sample extraction. A Sciex API 3000 triple quadrupole mass spectrometer with an atmospheric pressure chemical ionization (APCI) interface operated in positive ion mode was used for detection. Lower limits of quantification of 1.00 and 2.00 ng/ml were attained for STI571 and its metabolite, CGP 74588, respectively. The method proved to be rugged and allowed the simultaneous quantification of STI571 and CGP 74588 in monkey plasma. Herein, assay development, validation, and representative concentration-time profiles obtained from TK studies are presented.

This manuscript reports development and validation of an assay method in rat serum for the simultaneous estimation of C1, C2, and C3, in-house CDRI molecules, of the class of aryloxy-substituted aryl-piperazinyl derivatives. The assay was applied to determine pharmacokinetic data after simultaneous intravenous administration of these three compounds. A high-performance liquid chromatography assay method using isocratic elution and fluorescence (excitation, 250 nm; emission 350 nm) was developed for simultaneous estimation of all the three compounds in rat serum. Linearity was observed between 12.5 and 400 ng/ml for all the three compounds in serum. Recoveries were highly consistent over the concentration ranges for all the analytes. Variations in the intra- and inter-batch accuracy and precision were within the acceptable limits of +/-20% at the limit of quantitation, whereas at higher concentrations it was +/-15%. A mixture of the three compounds was administered intravenously to rats. Blood samples were collected over a period of 6 h and analyzed to determine serum levels and pharmacokinetics of each compound. The pharmacokinetics of the aforementioned three compounds was also determined after individual administration. The results obtained in the N-in-One dosing correlated well with discrete dosing of compounds. Based on the results obtained, C2 emerges to be the compound with appropriate pharmacokinetic parameters. Thus, the N-in-One method is a useful method for increasing the throughput to obtain the pharmacokinetic information.

CDRI-93/478 is a potent anti-ischemic and anti-hypertensive agent. This compound is in advanced stage of pre-clinical trials. A high-performance liquid chromatographic (HPLC) method was developed for the analysis of CDRI-93/478 in rat serum, a species used for safety evaluation. The HPLC analysis, applicable to 1 ml volumes of serum, involved double extraction of serum samples with diethyl ether at alkaline pH followed by separation on a spheri-5 cyano column and the use of fluorescence detector at excitation wavelength 250 nm and emission wavelength 372 nm. The method was sensitive with a limit of quantitation of 10 ng ml(-1) in rat serum and the recovery was more than 84%. The linearity was satisfactory as indicated by correlation of >0.99, in addition to the visual examination of the calibration curves. The precision and accuracy were acceptable as indicated by relative standard deviation (R.S.D.) ranging from 1.73 to 9.51%, bias values ranging from -7.31 to 8.68%. Moreover, CDRI-93/478 was stable in rat serum after being subjected to three freeze-thaw cycles. In-process stability evaluation showed the stability of the compound in processed samples lasted up to 168 h. The assay was found to be sensitive, specific, accurate, precise, and reliable for use in pharmacokinetic or toxicokinetic studies.

RGH-1756 (1-(2-methoxy-phenyl)-4-(4-[4-(6-imidazo[2,1-b]-thiazolyl)-phenoxy]-butyl)-piperazine dimethansulphonate) is a novel atypical antipsychotic candidate of Gedeon Richter Ltd. A new HPLC method has been developed and validated for the quantitative determination of RGH-1756 in dog and rat plasma. The compound and the internal standard are extracted from the biological samples by a simple and fast liquid--liquid extraction method, using 1-chlorobutane. The recovery for RGH-1756 is about 90%. The extracts are analyzed by reversed phase HPLC (column: Supelcosil-LC-18-DB 250*4.6 mm, 5 microm, eluent:acetonitrile:methanol:0.2 molar ammonium-acetate 40:25:35, lambda=254 nm). The assay is specific for RGH-1756. The standard curves are linear in the range between 10 and 2000 ng ml(-1). The overall precision (expressed as CV%) and accuracy (expressed as bias%) of quality controls and calibration standards are within 15%. The validated lower limit of quantification is 10 ng/ml. No indications have been found for possible instabilities of RGH-1756 in plasma, in the extraction solvent, or after repeated thawing-freezing cycles. The method has been succesfully applied for the bioavailability studies of RGH-1756 in the two animal species. In these studies results of the inprocess method validation have shown the reliability of the method, too. CV% of quality controls in the rat study has been found between 7.4 and 10.0%, in the dog study between 4.1 and 12.5%. The bias has ranged from 0.4 to 3.8% and from -4.5 to 1.2% in the rat and dog study, respectively.

A method for the simultaneous determination of the HIV protease inhibitors indinavir and L-756423, in human plasma has been developed. Plasma samples (0.5 ml) were extracted using a 3M Empore 96-well plate in the mixed phase cation exchange (MPC) format. The extraction method was automated through the application of both the Packard 204DT and TOMTEC Quadra 96 work stations, and the resulting extracts were analyzed using a PE-Sciex API-3000 LC-MS/MS with a heated nebulizer interface (500 degrees C). The assay was linear in the concentration range 1-2500 ng/ml for indinavir and 5 2500 ng/ml for L-756423 when 0.5-ml aliquots of plasma were extracted. Recoveries of indinavir and L-756423 were greater than 76 and 80%, respectively, over the calibration curve range when using the described sample preparation method. Within-batch precision and accuracy for the quantitation of indinavir over the range 1-2500 ng/ml were 5.4% R.S.D. or less and within 4.0%, respectively. Within-batch precision and accuracy for the quantitation of L-756423 over the range 5-2500 ng/ml were 5.3% R.S.D. or less and within 3.4%, respectively. Interbatch variability for the analysis of indinavir QC samples at low (3 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) were 3.2, 2.9, and 1.9%, respectively. Interbatch variability for the analysis of L-756423 QC samples at low (15 ng/ml), middle (250 ng/ml) and high (2250 ng/ml) concentration were 2.0, 2.5, and 3.3%, respectively. The validated assay was used in support of human clinical trials.

A simple reversed-phase high-performance liquid chromatography (HPLC) method with UV detection was developed and validated for the quantitation of SYN-2869, a novel triazole antifungal agent and its analogs in rat plasma. The method involved a simple precipitation of plasma protein with acetonitrile (1:10 ratio). The reconstituted sample after evaporation to dryness was injected onto a HPLC column. SYN-2869 and its analogs were separated from the matrix components on a symmetry C18 column using an aqueous mobile phase of acetonitrile and water with a flow rate of 1 ml min(-1). A step gradient of 40-80% acetonitrile eluted all four compounds. The run time was 30 min. The linear range was 0.5 10 microg ml(-1)(r2 > 0.999). The limit of quantitation was 0.5 microg ml(-1). The inter-day precision and accuracy for SYN-2869 standard concentration were from 1.9 to 8.5% and from 1.4 to +/- 4.40%, respectively. The precision and accuracy of intra-day quality control samples were from 4.6 to 5.2% and from 4.6 to 12%, respectively.

A stereoselective method based on high-performance liquid chromatography (HPLC) and ultraviolet detection at 235 nm for the separation of the four possible stereoisomers of compound 1 ((S-(R*,S*))-2-(4-((4-methylpiperazin-1-yl)carbonyl)phenoxy)-3,3-d iethyl-N-(1-(3,4-(methylenedioxy)phenyl)butyl)-4-oxo-1-azetidinecarbo xamide, L-694,458), a potent, selective, and orally active human leukocyte elastase (HLE) inhibitor, in human and monkey plasma has been developed. The molecule of 1 contains two chiral centers and is being developed as a single stereoisomer with the absolute configuration S and R in positions 'a' and 'b', respectively. Although the baseline separation of each of the two pairs of enantiomers (SS/RR and SR/RS) was achieved on a single chiral column (Chiralcel OD-H) using hexane methyl-t-butyl ether (MTBE)-methanol 80/10/10, (v/v/v) as a mobile phase (alpha(RS,SR) = 2.03, alpha(RR,SS) = 4.97), only partial separation of RS from RR was observed under these conditions (k'RS = 3.32, k'RR = 3.08). Baseline separation of all four stereoisomers from each other and from endogenous plasma components required the initial chromatography of the two diastereomeric racemates (SS/RR and SR/RS) on the achiral silica column (50 x 4.6 mm, 5 microm), followed by column switching and further separation of the stereoisomers on a Chiralcel OD-H column (250 x 4.6 mm, 5 microm) using isopropanol (IPA)-hexane diethylamine (DEA), 65/35/0.3, (v/v/v) on both columns as a mobile phase. The drug was extracted from basified (pH 11) plasma (1 ml) using liquid liquid extraction with MTBE. After evaporation of the extract to dryness, the residue was reconstituted in the mobile phase (200 microl) and part of the extract (125 microl) was injected into the HPLC system. Using this method, it was demonstrated that after oral dosing of monkeys at 40 mg kg(-1) with 1 the only stereoisomer detected in the post-dose plasma samples was the starting material 1, and no inversion of the configuration at positions 'a' and 'b' of 1 had occurred in vivo. Based on this observation, a non-chiral assay for 1 in human plasma was also developed. The method was validated in the concentration range 10-500 ng ml(-1) with the assay precision (expressed as the coefficient of variation, CV) better than 9% and assay accuracy in the range of 95-107% of the nominal concentrations at all concentrations within the standard curve range. The total run time in the non-chiral assay was 12 min. The details of both chiral and non-chiral methods are provided.

AD-5423, 2-(4-ethyl-1-piperazinyl)-4-(4-fluorophenyl)-5,6,7,8,9,10-hexahydrocy cloocta [b]pyridine, is a novel anti-psychotic agent. In order to investigate the pharmacokinetics of AD-5423, a simple and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of AD-5423 and its two N-oxidized metabolites (N-desethyl AD-5423 and AD-5423 N-oxide) in plasma. After pretreatment of a plasma sample by solid-phase extraction, AD-5423 and its metabolites were analyzed on a HPLC with fluorescence detection (335/410 nm). Chromatography was performed on two C18 reversed-phase columns connected by a switching system, with a mobile phase of acetonitrile-methanol-25 mM sodium phosphate buffer (pH 2.5) containing 25 mM sodium 1-heptanesulfonate (36:26:38 v/v/v). The method gives satisfactory accuracy and precision for the determination of AD-5423 and its metabolites. In human plasma, accurate determination are possible over the concentration ranges of 0.04-5 ng ml-1 for AD-5423 and 0.1-5 ng ml-1 for N-oxidized metabolites. The intra- and inter-day assay precision (R.S.D.) of AD-5423 (0.5 ng ml-1) were 3.6 and 7.2%, respectively. In plasma of experimental animals, the validated quantitative range are 0.1-100 ng ml-1 for both AD-5423 and its metabolites.

Inhibiting the action of platelet-activating factor (PAF) is a new therapeutic approach for the treatment of allergic disorders. SCH 44643 is a new orally-active antagonist of response to both PAF and histamine. This study was done to determine plasma drug concentrations using a GC method and to compare them to ex-vivo anti-PAF activity in the plasma of cynomolgus monkeys following a single oral (12.5 mg kg-1) administration. The GC method involved organic solvent extraction of monkey plasma followed by a GC analysis in a RTX-1 capillary column with a nitrogen/phosphorus detector. The method showed good precision (RSD < 8%) and accuracy (bias < 9%) with a limit of quantitation of 20 ng ml-1. The plasma profiles of SCH 44643 concentration and anti-PAF activity were very similar in each of the six monkeys. There was an excellent correlation (r = 0.9003) between anti-PAF activity and plasma concentration of SCH 44643, suggesting that the anti-PAF activity in cynomolgus monkeys was primarily due to unchanged SCH 44643, rather than its potential metabolite(s).

A new labelling approach of haptenic drugs with digoxigenin for the development of competitive enzyme immunoassay (EIA) is reported. It consists of the covalent linking of the hapten to the preactivated digoxigenin derivative and revealing the immune complexes with anti-digoxigenin Fab fragments coupled to alkaline phosphatase. This approach has been applied to the development of an EIA for the pharmacokinetic study of lesopitron (E-4424), a new anxiolytic agent. The assay involves a solid-phase immobilization of IgG purified from polyclonal antiserum developed against the butylamino derivative of lesopitron covalently linked to bovine serum albumin. The tracer consists of the covalent linking of the same butylamino derivative to digoxigenin-3-O-methylcarbonyl-epsilon-aminocaproic acid N-hydroxysuccinimide ester. The calibration curve for E-4424 from 12.5 to 6400 pg per well displays an ED50 of 34.5 pg per well, a slope factor of 0.86 and a minimum detectable dose of 4.1 pg per well. The accuracy and the precision of the assay assessed at three different concentrations of E-4424 (500, 1000 and 2000 pg ml-1) give a recovery higher than 95% and intra- and inter-assay RSDs lower than 5 and 10%, respectively. The specificity of the assay was demonstrated by a good correlation of the samples analysed by both HPLC and EIA. A kinetic profile of E-4424 in rats following an oral dose of 50 mg kg-1 has also been established.

A sensitive and specific quantitative method for the determination of zipeprol, a newly abused antitussive, in human fluids is described. Zipeprol and an internal standard, levallorphan, are isolated by a basic extraction and back-extraction process. The final extract is derivatizated with BSTFA + 1% TMCS and separated on a 12-m HP-1 capillary column. Drugs are detected by selected ion monitoring at m/z 335 and m/z 355 for zipeprol and the internal standard, respectively. The minimum detectable quantities are 0.6 and 0.4 ng ml-1, for zipeprol in plasma and urine, respectively. Relative standard deviations for within-run data are less than 6%.

An HPLC method was developed for the direct on-line radioactivity determination of [14C]-saterinone and its metabolites in biological canine fluids after intravenous and intraduodenal administration. After direct injection of 200 microliters of sample, the metabolites were separated on a semi-preparative reverse-phase column. The metabolites were identified by HPLC reference standards, enzymatic hydrolysis and mass spectrometry. Besides a small amount of unchanged saterinone, six metabolites could be detected, both in bile and urine. The main fraction (about 80-90% of the sum of detected metabolites) contained the phase II metabolites of saterinone, the sulphate and glucuronide. Ring hydroxylated saterinone and three metabolites that were not identified made up about 1-4% each. In plasma, only the major compounds could be detected because of the lower absolute concentrations. The metabolic pathway of saterinone in dogs was elucidated and compared with other species. Results from previous studies concerning a first-pass metabolism could be confirmed.