Liquid chromatography-negative ion electrospray tandem mass spectrometry method for the quantification of ezetimibe in human plasma

A simple, reliable and sensitive liquid chromatography-tandem mass spectrometry method (LC-MS/MS) was developed and validated for quantification of free and total ezetimibe in human plasma. The analyte and internal standard (13C6-ezetimibe) were extracted by liquid-liquid extraction with methyl tert-butyl ether. The reversed-phase chromatographic separation was performed on a Capcell C18 column, and the plasma extract was eluted with a gradient consisting of acetonitrile and 5 mM ammonium acetate. The analyte was detected using negative ionization by multiple reaction monitoring mode. The mass transition pairs of m/z 408.5-->270.8 and m/z 414.5-->276.8 were used to detect ezetimibe and internal standard, respectively. The assay exhibited linear ranges from 0.02 to 20 ng/ml for free ezetimibe and 0.25 to 250 ng/ml for total ezetimibe in human plasma. Acceptable precision and accuracy were obtained for concentrations of the calibration standard and quality control. The validated method was successfully used to analyze human plasma samples for application in a pharmacokinetic study.     

High performance liquid chromatography-tandem mass spectrometric determination of rupatadine in human plasma and its pharmacokinetics

A simple, rapid, sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the quantification of rupatadine in human plasma using estazolam as internal standard (IS). Following liquid-liquid extraction, the analytes were separated using a mobile phase of methanol-ammonium acetate (pH 2.2; 5mM) (50:50, v/v) on a reverse phase C18 column and analyzed by a triple-quadrupole mass spectrometer in the positive ion and multiple reaction monitoring (MRM) mode, m/z 416-->309 for rupatadine and m/z 295-->267 for the IS. The assay exhibited a linear dynamic range of 0.1-100 ng/ml for rupatadine in human plasma. The lower limit of quantification (LLOQ) was 0.1 ng/ml with a relative standard deviation of less than 20%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The validated LC-MS/MS method has been successfully applied to study the pharmacokinetics of rupatadine in healthy volunteers.     

Liquid chromatography/tandem mass spectrometry for the determination of carbamazepine and its main metabolite in rat plasma utilizing an automated blood sampling system

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous determination of carbamazepine and its main metabolite carbamazepine 10,11-epoxide in rat plasma is described. The method consists of a liquid-liquid extraction procedure and electrospray LC/MS/MS analysis. The chromatographic separation was achieved within 5 min using a C(8) (150 mm x 2.1mm) 5 microm column with a mobile phase composed of water/acetonitrile/acetic acid (69.5:30:0.5, v/v/v) at a flow rate of 0.4 ml/min. D(10)-carbamazepine is used as the internal standard for all compounds. Analytes were determined by electrospray ionization tandem mass spectrometry in the positive ion mode using selected reaction monitoring (SRM). Carbamazepine was monitored by scanning m/z 237-->194, carbamazepine 10,11-epoxide by m/z 253-->210 and d(10)-carbamazepine by m/z 247-->204. The lower limit of quantitation (LLOQ) is 5 ng/ml for each analyte, based on 0.1 ml aliquots of rat plasma. The extraction recovery of analytes from rat plasma was over 87%. Intra-day and inter-day assay coefficients of variations were in the range of 2.6-9.5 and 4.0-9.6%, respectively. Linearity is observed over the range of 5-2000 ng/ml. This method was used for pharmacokinetic studies of carbamazepine and carbamazepine 10,11-epoxide in response to two different blood sampling techniques (i.e., manual sampling versus automated sampling) in the rat. Several differences between the two sampling techniques suggest that the method of blood collection needs to be considered in the evaluation of pharmacokinetic data.     

Development and validation of an automated SPE-LC-MS/MS assay for valdecoxib and its hydroxylated metabolite in human plasma

A sensitive and specific liquid chromatography-tandem mass spectrometry assay was developed to quantitate valdecoxib (I) and its hydroxylated metabolite (II) in human plasma. The analytes (I and II) and a structurally analogue internal standard (IS) were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The chromatographic separation was performed on a narrow-bore reverse phase Zorbax XDB-C(8) HPLC column with a mobile phase of acetonitrile:water (50:50, v/v) containing 10 mM ammonium acetate. The analytes were ionized using negative electrospray mass spectrometry, then detected by multiple reaction monitoring (MRM) with a tandem mass spectrometer. The precursor to product ion transitions of m/z 313-->118 and m/z 329-->196 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-200 ng/ml of I and II in human plasma with absolute recoveries from plasma at 91 and 86%, respectively. The lower limit of quantitation was 0.5 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.5-200 ng/ml). Sample analysis time for each injection was 5 min, a throughput of 70 human plasma standards and samples per run was achieved. The assay has been successfully used to analyze human plasma samples to support clinical phase I and II studies.     

A sensitive LC/MS/MS method using silica column and aqueous-organic mobile phase for the analysis of loratadine and descarboethoxy-loratadine in human plasma

A sensitive method using liquid chromatography with tandem mass spectrometric detection (LC/MS/MS) was developed and validated for the simultaneous analysis of antihistamine drug loratadine (LOR) and its active metabolite descarboethoxy-loratadine (DCL) in human plasma. Deuterated analytes, i.e. LOR-d(3) and DCL-d(3) were used as the internal standards (I.S.). Analytes were extracted from alkalized human plasma by liquid/liquid extraction using hexane. The extract was evaporated to dryness under nitrogen, reconstituted with 0.1% (v/v) of trifluoroacetic acid (TFA) in acetonitrile, and injected onto a 50 x 3.0 mm I.D. 5 microm, silica column with an aqueous-organic mobile phase consisted of acetonitrile, water, and TFA (90:10:0.1, v/v/v). The chromatographic run time was 3.0 min per injection and flow rate was 0.5 ml/min. The retention time was 1.2 and 2.0 min for LOR and DCL, respectively. The tandem mass spectrometric detection was by monitoring singly charged precursor-->product ion transitions: 383-->337 (m/z) for LOR, 311-->259 (m/z) for DCL, 388-->342 (m/z) for LOR-d(3), and 316-->262 (m/z) for DCL-d(3). The low limit of quantitation (LLOQ) was 10 pg/ml for LOR and 25 pg/ml for DCL. The inter-day precision of the quality control (QC) samples was 3.5-9.4% relative standard deviation (R.S.D.). The inter-day accuracy of the QC samples was 99.0-107.9% of the nominal values.     

Development of a rapid and sensitive LC-MS/MS assay for the determination of sorafenib in human plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometric (LC/MS/MS) assay was developed for the quantitative determination of sorafenib in human plasma. Sample pretreatment involved simple protein precipitation by the addition of 0.5 mL acetonitrile, containing internal standard ([2H3, 15N] sorafenib), to 50 microL of plasma sample volume. Separation was achieved on a Waters SymmetryShield RP8 (2.1 mm x 50 mm, 3.5 microm) column at room temperature using an isocratic elution method with acetonitrile/0.1% formic acid in water: 65/35 (v/v) at a flow rate of 0.25 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 464.9 --> 252.0 (sorafenib) and m/z 469.0 --> 259.0 (internal standard). Calibration curves were linear in the concentration range of 5-2000 ng/mL. The accuracy and precision values, calculated from three different sets of quality control samples analyzed in quintuplicate on six different days, ranged from 92.86% to 99.88% and from 1.19% to 4.53%, respectively.     

Rapid quantification of gabapentin in human plasma by liquid chromatography/tandem mass spectrometry

A simple, sensitive and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of gabapentin, a new antiepileptic drug, in human plasma using its structural analogue, 1,1-cyclohexane diacetic acid monoamide (CAM) as internal standard. The method involved a simple protein precipitation by means of acetonitrile followed by a rapid isocratic elution with 10mM ammonium formate buffer/acetonitrile (20/80, v/v, pH 3.0) on Waters Symmetry C(18 reversed phase chromatographic column and analyzed by mass spectrometry in the multiple reaction monitoring mode. The precursor to product ion transitions of m/z 172-->154 and m/z 200-->182 were used to measure the analyte and the IS, respectively. The assay exhibited a linear dynamic range of 40-10000 ng/mL for gabapentin in human plasma. The limit of detection and lower limit of quantification in human plasma were 10 and 40 ng/mL, respectively. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.     

A validated SPE-LC-MS/MS assay for Eplerenone and its hydrolyzed metabolite in human urine

An automated LC-MS/MS assay was validated to quantitate the first selective aldosterone blocker Eplerenone (I) and its hydrolyzed metabolite (II) in human urine. After the addition of the stable isotope labeled internal standards, human urine samples were extracted on a C(18) solid phase extraction (SPE) cartridge using a Zymark RapidTrace automation system. The extraction eluates were diluted with 20 mM ammonium acetate aqueous solution and directly injected onto the LC-MS/MS system. The chromatographic separation was performed on a reverse phase Zorbax XDB-C(8) HPLC column (2.1 x 50 mm, 5 microm) with a mobile phase of acetonitrile:water (40:60, v/v) containing 10 mM ammonium acetate (pH 7.4). I and II were ionized using positive and negative ionization mass spectrometry, respectively, to achieve the best sensitivity. The ionization polarity was switched during the run at approximately 2.5 min after the injection. Multiple reaction monitoring (MRM) with a tandem mass spectrometer was used to detect the analytes. The precursor to product ion transitions of m/z 415-->163 and m/z 431-->337 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 50-10000 ng/ml of urine for both of I and II. The lower limit of quantitation (LLOQ) was 50 ng/ml for I and II. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. Sample analysis time for each injection was 5 min; a throughput of 100 human urine standards and samples per run was achieved.     

Determination of cetirizine in human plasma using high performance liquid chromatography coupled with tandem mass spectrometric detection: application to a bioequivalence study

A rapid, sensitive and selective HPLC-MS/ MS method was developed and validated for the quantification of cetirizine dihydrochloride (CAS 83881-51-0) in human plasma using mosapride citrate as internal standard (IS, CAS 112885-42-4). Following liquid-liquid extraction, the analytes were separated using a mobile phase consisting of methanol and aqueous ammonium acetate solution (10 mM) (60:40, v/v) on a reverse phase C18 column and analyzed by a triple-quadrupole mass spectrometer in the selected reaction monitoring (SRM) mode using the respective [M+H]+ ions, m/z 398 --> 201 for cetirizine and m/z 422 --> 198 for mosapride. The analysis time for each run was 8.0 min. The assay exhibited a linear dynamic range of 0.5-500 ng/ml for cetirizine dihydrochloride in human plasma. The lower limit of quantification (LLOQ) was 0.5 ng/ml with a relative standard deviation of less than 15% (all the concentration data in this study related to the salt (cetirizine dihydrochloride)). Acceptable precision and accuracy were obtained for concentrations over the standard curve range. It is the first time that the validated HPLC-MS/MS method has been successfully applied to a bioequivalence study in 20 healthy male Chinese volunteers.     

Liquid chromatography-tandem mass spectrometry method for the quantification of deglymidodrine in human plasma

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry method was developed for quantification of deglymidodrine in human plasma. The plasma samples were pretreated by protein precipitation with trichloroacetate. The chromatographic separation was performed on reversed phase Aquasil C18 column, and the plasma extraction was eluted with a mobile phase solution consisting of acetonitrile (containing 0.02% formic acid) and water (containing 0.02% formic acid). The molecular ion of analyte was detected in positive ionization by multiple reaction monitoring. The mass transitions of m/z 198.4--> 148.1 and m/z 212.4--> 162.3 were used for detection of deglymidodrine and its internal standard, respectively. The assay exhibited linear ranges from 0.25 to 32 ng/ml for the analyte in human plasma. Acceptable precision and accuracy were obtained for concentrations of quality control (QC) samples. The proposed method has been successfully used to analyze human plasma samples for application in oral pharmacokinetic study.     

Quantitative determination of rosuvastatin in human plasma by ion pair liquid-liquid extraction using liquid chromatography with electrospray ionization tandem mass spectrometry

A simple and sensitive liquid chromatography/tandem mass spectrometry method was developed and validated for the quantification of rosuvastatin in human plasma. After being treated with acetic acid and tetrabutyl ammonium hydroxide, the analyte was extracted by simple one-step liquid-liquid extraction with the internal standard (IS: estrone). The chromatographic separation was performed on a Phenomenex Luna C18 column with a mobile phase consisting of 2% formic acid/methanol (20:90, v/v) at a flow rate of 1.00 mL/min with a split of 200 microL to mass spectrometer. The retention time of rosuvastatin and internal standard was 2.3 and 3.4 min, respectively. Triple-quadrupole MS/MS detection was operated in positive mode by monitoring the transition of m/z 482-->258 for rosuvastatin and m/z 271-->253 for IS. Validation results indicated that the lower limit of quantification (LLOQ) was 0.1 ng mL(-1) and the assay exhibited a linear range of 0.1-20 ng mL(-1) and gave a correlation coefficient (r) of 0.9990 or better. Inaccuracy was less than 8.4% and imprecision less than 12.8% at all tested concentration levels. The analyte was stable in human plasma following three freeze/thaw cycles and for up to 8 weeks following storage at -20 degrees C. The assay was successfully applied to the analysis of rosuvastatin in human plasma samples derived from clinical pre-trials.     

液相色谱-串联质谱法同时测定人血浆中二甲双胍和格列吡嗪

建立了快速、灵敏的液相色谱-串联质谱法测定人血浆中的二甲双胍和格列吡嗪。血浆样品经0.3%甲酸-乙腈(v/v)沉淀蛋白后，以乙腈-水-甲酸(70∶30∶0.3，v/v/v)为流动相，流速为0.50 mL·min^-1。Zorbax Extend C₁₈柱分离，采用大气压化学电离源；以选择反应监测(SRM)方式进行正离子检测。用于定量分析的离子反应分别为m/z 130→m/z 60(二甲双胍)，m/z 446→m/z 321(格列吡嗪)和m/z 256→m/z 167(内标，苯海拉明)。测定血浆中二甲双胍的线性范围为2.00～2 000 ng·mL^-1， 定量下限为2.00 ng·mL^-1； 格列吡嗪的线性范围为1.00～1 000 ng·mL^-1， 定量下限为1.00 ng·mL^-1。该方法专属性好，灵敏度高，准确快捷，适用于二甲双胍和格列吡嗪的临床药代动力学研究。     

Simultaneous quantitative analysis of oxcarbazepine and 10,11-dihydro-10-hydroxycarbamazepine in human plasma by liquid chromatography-electrospray tandem mass spectrometry

A fast and sensitive method to quantify oxcarbazepine (OXC) and its active metabolite, 10,11-dihydro-10-hydroxycarbamazepine (MHD) in human plasma using HPLC-MS/MS has been developed. The method involved liquid-liquid extraction (LLE), with diethyl ether-diclhoromethane (60:40v/v) using deuterade carbamazepine (d10-carbamazepine) as internal standard (IS). The analytes and IS were separated using an isocratic mobile phase (acetonitrile/water (50:50v/v)+20 mM acetic acid) on the analytical column Phenomenex Luna C18 5 microm (150 mm x 4.6 mm) at room temperature. Detection was performed by a Micromass Quatro LC mass spectrometer in the reaction monitoring mode using positive electrospray ionization (ESI+). The MS-MS ion transition monitored were m/z 253>208 for OXC, m/z 255>194 for MHD and m/z 247>204 for IS. Over the range 20-5250 ng/ml for OXC and 40-10,500 ng/ml for MHD, the calibration curves were defined by the following equations: y = 0.00568 + 0.00296x -5.70e - 8x(2) and y = 0.00749 + 0.00178x - 5.70e - 8x(2) for OXC and MHD, respectively. All coefficient of determination (r(2)) were close to unity (0.9986-0.9994). The lower limits of quantification obtained as a result of the LLE procedure was 20 ng/ml for OXC and 40 ng/ml for MHD. The statistical evaluation of the developed method was conducted by examining within-batch and between-batch precision data, which were within the required limits. The suitability of the assay for pharmacokinetics studies was determined by measuring OXC and MHD concentration after administration of a single 10 ml of OXC oral suspension (6%) in plasma human of healthy volunteers.     

Electrospray LC-MS/MS quantitation,stability, and preliminary pharmacokinetics of bradykinin antagonist polypeptide B201 (NSC 710295) in the mouse

B201 (NSC 710295), [SUIM-(Darg-Arg-Pro-Hyp-Gly-Igl-Ser-Digl-Oic-Arg)(2)], a third generation of bradykinin (BK) antagonist, has been found to possess high potency. We report the development of a highly sensitive electrospray LC-MS/MS assay method for the analysis of B201 in plasma for the first time, using an ion-trap mass spectrometer. Human or mouse plasma (0.2 ml) was spiked with B201 and the internal standard, substance P. The compounds were extracted with a preconditioned C-18 reversed-phase column and analyzed by LC-MS/MS. The analytes were separated on a 50 x 2 mm (i.d.) BetaBasic C8 column, using a gradient elution. The positive ion selected reaction monitor mode was used monitoring the transitions of ions at m/z 938.9(3+)-->816.0(2+) for B201 and 674.3(2+)-->665.7(2+) for substance P. Assay validation was performed, and the limit of quantitation (LOQ) for B201 was found to be 1 ng/ml for human plasma and 2.5 ng/ml for mouse plasma. The recovery was 78% for B201 and 88% for substance P. The assay was linear from 2.5 to 1500 ng/ml for mouse plasma monitored. Using a 0.2 ml plasma, the within-day CVs were 9.3% at 2.5 ng/ml, 6.5% at 100 ng/ml, and 3.8% at 1000 ng/ml for human plasma (n=6). For mouse plasma, the respective within-day CVs were 17.6, 9.6, and 6.2% (n=6). The between-day CVs for human plasma were 8.2, 10.9, and 2.4%, respectively, (n=3) and the respective values for mouse plasma were 11.9, 8.6 and 6.5% (n=6). Pharmacokinetics of B201 in the mouse was studied following i.v. administration at 5 mg/kg and found to conform to a two-compartment model with an initial half-life of 14 min and a terminal half-life of 44 h. Plasma B201 peak level was detected at microg/ml range and the levels were detectable for a least 24 h. Preliminary oral bioavailability was found to be about 1%. This method demonstrates that an ion trap mass spectrometer can be a powerful tool to quantify large peptides at low nanogram per milliliter with a non-isotopically labeled internal standard.     

Determination of fexofenadine in human plasma using 96-well solid phase extraction and HPLC with tandem mass spectrometric detection

A fast and sensitive HPLC-MS/MS method, utilizing atmospheric pressure chemical ionization, for the determination of fexofenadine in human plasma is described. A deuterated analog, d6-fexofenadine is used as the internal standard (IS). Plasma samples are prepared using 96-well solid phase extraction with plates containing Waters Oasis HLB sorbent. The analytes are chromatographed on a Restek Ultra IBD column (3.2 mm x 50 mm, 3 microm) using a mobile phase consisting of a mixture of 90% acetonitrile and 10% 10 mM ammonium acetate buffer and 0.1% formic acid. Quantitation of the analyte is based on the response from the multiple reaction monitoring of the precursor to product ion pairs for fexofenadine (m/z 502 --> 466) and d6-fexofenadine (m/z 508 --> 472). The assay has been validated over the concentration range of 1-200 ng/ml based on the analysis of 0.5 ml aliquots of plasma. Within-day assay accuracy was between 97 and 102% of nominal, while within-day precision was better than 3.5% CV at all points on the standard curve. Analyte extraction recovery was better than 70% over the range of the standard curve. The method was found to be suitable for the analysis of human plasma samples obtained 24 h following the administration of a single 60 mg dose of fexofenadine.     

LC-MS determination and relative bioavailability of doxazosin mesylate tablets in healthy Chinese male volunteers

This study aims to develop a standard protocol for the relative bioavailability testing of doxazosin mesylate tablets. For this purpose, a simple rapid and selective LC-MS method using a single quadrupole mass spectrometer was developed and validated to determine the concentration of doxazosin mesylate in human plasma. Using this method, we carried out a study of relative bioavailability. N-Hexylane-tertiary butyl methyl ether (1:1, v/v) was used to extract doxazosin mesylate and terazosin (internal standard, I.S.) from an alkaline plasma sample. LC separation was performed on a Thermo Hypersil-Hypurity C18 (5 microm, 150 mm x 2.1mm) using aqueous solution (20 mmol/l ammonium acetate, pH 4.28), methanol and acetonitrile (55:10:35, v/v/v) as the mobile phase. The retention time of doxazosin and the internal standard was 2.7 and 1.8 min, respectively. Quadrupole MS detection was done by monitoring at m/z 388 (M+1) corresponding to doxazosin mesylate and at m/z 452 (M+1) for I.S. The assay method described above showed acceptable precision, accuracy, linearity, stability, and specificity. The bioavailability of doxazosin mesylate was evaluated in 12 healthy Chinese male volunteers. The following pharmacokinetic parameters were elucidated after administering a single dose of 4 mg doxazosin. The area under the plasma concentration versus time curve from time 0 to 72 h (AUC(0-72 h)) 743.4+/-149.5 ngh/ml; peak plasma concentration (C(max)) 47.66 ng/ml; time to C(max) (T(max)) 3.0+/-1.0 h; and elimination half-life (t(1/2)) 18-20 h. The method was successfully used to determine the relative bioavailability of doxazosin mesylate.     

Quantitative determination of paclitaxel in human plasma using semi-automated liquid-liquid extraction in conjunction with liquid chromatography/tandem mass spectrometry

This paper describes a high-throughput sample preparation procedure combined with LC-MS/MS analysis to measure paclitaxel in human plasma. Paclitaxel and an internal standard were extracted from plasma by a semi-automated robotic method using liquid-liquid extraction. Thereafter compounds were separated on a RP C18 column. Detection was by a PE Sciex API 3000 mass spectrometer equipped with a TurboIonSpray interface. The compounds were detected in positive ion mode using the mass transition m/z 854.6-->286.2 and m/z 831.6-->263.2 for paclitaxel and the internal standard, respectively. The limit of quantitation for paclitaxel was 1 ng/ml with an imprecision of 5.2% following extraction of 0.1 ml of plasma. Linearity was confirmed over the whole calibration range (1-1000 ng/ml) with correlation coefficients higher than 0.99 indicating good fits of the regression models. The inter and intra-day precision was better than 9.5% and the accuracy ranged from 90.3 to 104.4%. The assay was simple, fast, specific and exhibited excellent ruggedness.     

A rapid and sensitive method for determination of dimethyl benzoylphenyl urea in human plasma by using LC/MS/MS

Dimethyl benzoylphenyl urea (BPU), a poorly water-soluble benzoylphenyl urea derivative, inhibits tubulin polymerization and causes microtubule depolymerization in vitro with activity against solid tumors. BPU is currently being tested in Phase I clinical trials. A rapid, sensitive and specific method using LC/MS/MS has been developed for the quantitation of BPU in human plasma to perform pharmacokinetic (PK) and pharmacodynamic (PD) studies of BPU administered orally once a week. BPU is extracted from plasma into acetonitrile-n-butylchloride and separated on a Waters X-Terra MS C18 (50 x 2.1 mm, 3.5 microm) column with acetonitrile/water mobile phase (80:20, v/v) containing 0.1% formic acid using isocratic flow at 0.15 ml/min for 5 min. The analyte of interest was monitored by tandem-mass spectrometry with electrospray positive ionization with a cone voltage 15 V for BPU and 30 V for the internal standard, paclitaxel. The detector settings allowed the monitoring of the [MH](+) ion of BPU (m/z 470.3) and the [MH](+) of internal standard paclitaxel (m/z 854.5), with subsequent monitoring of the product ions of BPU (m/z 148.0) and paclitaxel (m/z 286.1). Calibration curves were generated over the range of 0.05-10 ng/ml with values for coefficient of determination of >0.99. The values for precision and accuracy were <20 and < or =15%, respectively. Following administration of BPU 5 mg as a weekly oral dose to a patient with advanced solid tumor malignancies, the maximum plasma concentration was 6.5 ng/ml and concentrations were quantifiable up to 173 h after administration. The lower limit of quantitation (LLOQ) of 0.05 ng/ml allows for successful measurement of plasma concentrations in patients receiving therapy with BPU as a once weekly oral dose.     

Simple, sensitive and rapid LC-MS/MS method for the quantitation of cerivastatin in human plasma--application to pharmacokinetic studies

A simple and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for estimation of cerivastatin (I) in human plasma, a potent hydroxy-methylglutaryl-coenzyme A reductase inhibitor. The analyte and internal standard (atorvastatin, II) were extracted by liquid/liquid extraction with diethyl ether/dichloromethane (70/30, v/v). The chromatographic separation was performed on reverse phase Xterra ODS column with a mobile phase of water/acetonitrile (30/70, v/v) with 0.03% formic acid. The protonated analyte was quantitated in positive ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 460.4 --> 356.3 and 559.2 --> 440.3 were used to measure I and II, respectively. The lower limit of quantitation was 10pg/mL with a relative standard deviation of less than 15%. Acceptable precision and accuracy were obtained for concentrations over the calibration curve ranges (0.01-10ng/mL). Sample analysis time of 2min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The assay can be used to analyze human plasma samples to support phase I and II clinical studies.