A highly sensitive LC-MS/MS method for the determination of 21-hydroxy deflazacort in nude mice plasma and its application to a pharmacokinetic study

In the current study, we established and validated a simple and sensitive liquid chromatography-tandem mass spectrometricmethod for the determination of 21-hydroxy deflazacort in nude mice plasma, and such a method was applied to a pharmacokinetic study. Using betamethasone as the internal standard, the plasma samples were pre-treated by precipitation with acetonitrile and then analyzed on a reversed-phase C₁₈ column (50 mm×2 mm, 5 μm) with a mobile phase consisting of acetonitrile and 4.0 mM ammonium formate (pH was adjusted to 3.5 with formic acid (40:60, v/v)). The analyte was detected by a triple quadrupole tandem mass spectrometer using electrospray, and multiple reaction monitoring was employed to select 21-hydroxy deflazacort at m/z 400.2/124.0 and betamethasone at m/z 393.3/147.0 in the positive ion mode. The calibration curves were linear (r>0.99) over the range of 0.5–400 ng/mL. The intra- and inter-day precisions and accuracies were 4.5%–10.1% and –1.7%~10.7% respectively. This method was successfully applied to a preclinical pharmacokinetic study of deflazacort on female nude mice administered with a single oral dose of 4 mg/kg deflazacort, and its pharmacokinetics was characterized by a two-compartment model with first-order absorption.     

A liquid chromatography-tandem mass spectrometric method for the determination of axitinib in nude mouse plasma: development,validation and application to a pharmacokinetic study

In the present study, a simple, rapid, and sensitive liquid chromatography-tandem mass spectrometric method for the determination of axitinib in nude mouse plasma was developed, validated, and applied to a pharmacokinetic study. Plasma samples were pre-treated by protein precipitation with acetonitrile spiked with erlotinib as an internal standard. The chromatographic separation was accomplished by using a reversed phase C₁₈ column (50 mm×2 mm, 5 μm) with a simple mobile phase system composed of methanol and water (60:40, v/v) at an isocratic flow rate of 0.4 mL/min. The analyte was detected by a triple-quadrupole tandem mass spectrometer via electrospray ionization and multiple reaction monitoring was employed to select both axitinib and erlotinib in the positive ion mode. The calibration curves were linear (r>0.99) ranging from 1 to 1000 ng/mL, and the lowest level of this range was the lower limit of quantification. The intra­ and inter­day precision were 7.7%-12.0%, and the accuracies ranged from 88.6% to 110.4%. This method was successfully applied to a preclinical pharmacokinetic study on female nu/nu nude mice administrated with a single oral dose of axitinib at 120 mg/kg, and the pharmacokinetics was characterized by a one-compartment model with first-order absorption.     

液相质谱串联法同时测定舒尼替尼及其活性代谢产物SU12662在BABL/c裸鼠血浆中的浓度及其药物动力学研究(英文)

本研究建立并验证了一种灵敏、快速、简单的液质联用方法,用于同时测定BABL/c裸鼠血浆中舒尼替尼及其活性代谢产物SU12662的药物浓度。血浆样品采用蛋白沉淀方法处理,并使用帕唑帕尼作为内标。采用C18反相柱进行分离,流动相为10 mM甲酸胺–乙腈(65:35,v/v,pH 3.25),流速0.5 m L/min。所有化合物均采用电喷雾电离源,正离子方式检测。舒尼替尼及SU12662的最低定量下限均为0.5 ng/m L,线性范围均为0.5–1000 ng/m L(r>0.99)。该方法对舒尼替尼及SU12662的测定均具有良好准确度以及可靠的日内、日间精密度,方法稳定性良好,无明显基质效应。此方法成功用于BABL/c裸鼠口服20 mg/kg舒尼替尼的药物代谢动力学研究。     

液质联用法同时测定埃罗替尼及其活性代谢产物OSI-420在BALB/c裸鼠体内的浓度及其药代动力学研究(英文)

本试验建立了一种简单快速灵敏的液质联用方法, 用以同时测定裸鼠血浆内埃罗替尼及其活性代谢物OSI-420的浓度。采用液液萃取法从血浆中提取埃罗替尼, OSI-420和内标普萘洛, 用C18反相柱进行分离, 流动相为乙腈-5 mM甲酸铵 (35:65, v/v, pH = 3.0)。所有化合物均采用电喷雾电离源, 正离子方式检测。埃罗替尼和OSI-420的最低定量下限均为0.5 ng/mL。埃罗替尼的准确度在0.07%-8.00%范围内, OSI-420准确度在-2.83%-6.67%范围内; 埃罗替尼精密度在2.28%-15.12%范围内, OSI-420精密度在1.96%-11.50%范围内。此方法应用于BALB/c裸鼠口服12.5 mg/kg埃罗替尼的药代动力学研究中, 并用二室模型拟合埃罗替尼的药代动力学, 一室模型拟合OSI-420的药代动力学。代谢为OSI-420的埃罗替尼占埃罗替尼总量的10%, 比文献中的这一比值大一倍, 表明种属间埃罗替尼的代谢存在差异。     

LC-MS/MS法测定人血浆中甘草次酸及其临床药代动力学研究

目的建立人血浆中甘草次酸的LC-MS/MS测定方法,研究男性健康志愿者单剂量服用甘草酸二铵胶囊,其代谢产物甘草次酸体内药代动力学行为。方法健康男性志愿者单剂量口服甘草酸二铵胶囊150 mg,血浆样品经乙酸乙酯提取,进行LC-MS/MS分析。色谱柱为Agilent ZORBAXSB C18(3.0×100 mm,5μm),流动相为甲醇∶乙腈∶醋酸铵缓冲液(5 mmol.L-1醋酸铵,0.2%冰醋酸)(15∶60∶25,V/V/V),检测离子为m/z469.4/355.2(甘草次酸)、m/z358.9/279.9(内标泼尼松龙)。测定甘草次酸血药浓度,计算其药代动力学参数。结果在1.5～192μg.L-1内,甘草次酸与内标的峰面积比值与浓度的线性关系良好,定量限为1.5μg.L-1,提取回收率为77.14%～83.64%。人体中甘草次酸药代动力学参数:Cmax为(73.85±25.25)μg.L-1,Tmax为(11.50±3.07)h,T21β为(11.82±3.56)h,AUC0-60为(1252.49±489.06)μg.h.L-1。结论建立的LC-MS/MS分析方法准确灵敏,适于临床药代动力学研究。口服甘草酸二铵胶囊,其代谢产物甘草次酸在体内的药代动力学特点是达峰时间长,约占受试者总人数50%的药时曲线有双峰现象。     

Development and validation of an LC–MS/MS method for quantification of NC-8 in rat plasma and its application to pharmacokinetic studies

ent-16-Oxobeyeran-19-N-methylureido (NC-8) is a recently synthesized derivative of iso-steviol that showed anti-hepatitis B virus (HBV) activity by disturbing replication and gene expression of the HBV and by inhibiting the host toll-like receptor 2/nuclear factor-κB signaling pathway. To study its pharmacokinetics as a part of the drug development process, a highly sensitive, rapid, and reliable liquid chromatography tandem mass spectrometry (LC–MS/MS) method was developed and validated for determining NC-8 in rat plasma. After protein precipitation extraction, the chromatographic separation of the analyte and internal standard (IS; diclofenac sodium) was performed on a reverse-phase Luna C₁₈ column coupled with a Quattro Ultima triple quadruple mass spectrometer in the multiple-reaction monitoring mode using the transitions, m/z 347.31 → 75.09 for NC-8 and m/z 295.89 → 214.06 for the IS. The lower limit of quantitation was 0.5 ng/mL. The linear scope of the standard curve was between 0.5 and 500 ng/mL. Both the precision (coefficient of variation; %) and accuracy (relative error; %) were within acceptable criteria of <15%. Recoveries ranged from 104% to 113.4%, and the matrix effects (absolute) were nonsignificant (CV ≤ 6%). The validated method was successfully applied to investigate the pharmacokinetics of NC-8 in male Sprague–Dawley rats. The present methodology provides an analytical means to better understand the preliminary pharmacokinetics of NC-8 for investigations on further drug development.     

LC-MS／MS测定人血浆中甘草次酸的浓度及其在药代动力学中的应用(英文)

建立一种灵敏度高、重现性好的高效液相色谱-质谱法（LC-MS/MS）测定人血浆中甘草次酸的浓度,并用于甘草酸铵的人体药动学研究。采用液-液萃取法进行血浆样品预处理,色谱柱为C₁₈柱,流动相为乙腈-5mmol/L乙酸铵（70:30,v/v）,流速0.8mL/min。采用负离子模式,多离子监测（MRM）方式进行检测,甘草次酸与内标甲砜霉素离子对质核比（m/z）分别为469.3→355.3、354.1→185.0。方法学验证表明此方法特异性强、灵敏度高、准确度与精密度符合要求,线性范围为0.5-500ng/mL,血浆样本经两次冻融及冷冻稳定良好,可以用于甘草酸铵的人体药代动力学研究。健康志愿者口服75mg甘草酸铵后,活性代谢产物甘草次酸的药动学参数如下:AUC_0-t（3457.26±1999.01）ng·h/mL、AUC_0-∞（3708.85±2428.36）ng·h/mL、MRT_0-t（19.69±4.03）h、MRT_0-∞（22.83±8.45）h、t_1/2Z（11.71±7.77）h、T_max（13.40±4.84）h、CLz/F（29±17±19±82）L/h、Vz/F（487.38±518.07）L、C_max（215.85±99.88）ng/mL。     

A rapid LC-MS/MS method for simultaneous determination of quetiapine and duloxetine in rat plasma and its application to pharmacokinetic interaction study

Combinations of new antidepressants like duloxetine and second-generation antipsychotics like quetiapine are used in clinical treatment of major depressive disorder, as well as in forensic toxicology scenarios. The drug–drug interaction (DDI) between quetiapine and duloxetine is worthy of attention to avoid unnecessary adverse effects. However, no pharmacokinetic DDI studies of quetiapine and duloxetine have been reported. In the present study, a rapid and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of quetiapine and duloxetine in rat plasma. A one-step protein precipitation with acetonitrile was applied for sample preparation. The analytes were eluted on an Eclipse XDB-C₁₈ column using the mixture of acetonitrile and 2 mM ammonium formate containing 0.1% formic acid at a gradient elution within 6.0 min. Quantification was performed in multiple-reaction-monitoring mode with the ion transitions m/z 384.4 → 253.2 for quetiapine, m/z 298.1 → 154.1 for duloxetine and m/z 376.2 → 165.2 for IS (haloperidol), respectively. Good linearity was obtained in the range of 0.50–100 ng/mL for quetiapine (r² = 0.9972) and 1.00–200 ng/mL for duloxetine (r² = 0.9982) using 50 μL of rat plasma, respectively. The method was fully validated with accuracy, precision, matrix effects, recovery and stability. The validated data have met the acceptance criteria in FDA guideline. The method was applied to a pharmacokinetic interaction study and the results indicated that quetiapine had significant effect on the enhanced plasma exposure of duloxetine in rats under combination use. This study could be readily applied in therapeutic drug monitoring of major depressive disorder patients receiving such drug combinations.     

Determination of fexofenadine in human plasma by LC-MS/MS and its application in pharmacokinetic study

This study presented a simple, rapid, and sensitive liquid chromatography analytical method employing tandem mass spectrometry (LC-MS/MS) to determine fexofenadine in human plasma. After the de-proteination procedure with acetonitrile, chromatographic separation of fexofenadine was performed using a reversed-phase Eclipse XDB-C₈ column with a mobile phase consisted of 1 mmol/L ammonium acetate buffer solution containing 0.2% formic acid-methanol (45:55, v/v). Fexofenadine was quantified using tandem mass detection in the electrospray ionization (ESI) positive ion mode. The flow rate of the mobile phase was 1 mL/min, and the retention times of fexofenadine and the internal standard (IS, losartan) were 1.76 min and 2.65 min, respectively. The calibration curve was linear over the plasma concentration range of 1-1000 ng/mL. The relative standard deviations of intra- and inter-batches were less than 10.4% and 15.4%, respectively. The LC-MS/MS method reported in this study showed higher sensitivity for the quantification of fexofenadine in human plasma than that shown by previously described analytical methods. Lastly, the method was successfully applied to the pharmacokinetic of fexofenadine in healthy Taiwan volunteers.     

Development and validation of a LC-MS/MS method with electrospray ionization for determination of LASSBio-579 in rat plasma

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.     

An established LC-MS/MS method and a developed PK model for the study of pharmacokinetic properties of benapenem in infected mice

Benapenem is a new parenteral beta-lactam antibacterial with a broad antibacterial spectrum. In the present study, we developed and validated a simple, rapid and sensitive assay method using D6-benapenem as internal standard (IS) after one-step precipitation with methanol to determine benapenem in the plasma of infected mice. Separation was achieved on a reverse phase C₁₈ column with a mobile phase composed of acetonitrile containing 0.2% formic acid–water (0.2% formic acid) and 10 mmol/L ammonium acetate in gradient elution mode. A triple quadrupole tandem mass spectrometer with electrospray ionization source was used as detector and operated by multiple reaction monitoring (MRM) in the positive ion mode. Calibration curves were linear (r>0.99) between 10 and 2000 ng/mL. The quantitative limit was 10 ng/mL, and the intra- and inter- precisions were <4.85% and <1.47%, respectively. The extraction recovery of benapenem and IS was 97.07%–107.09% and 92.47%–111.59%, respectively. The intra- and inter- accuracies were –9.70%– –11.00%, and the matrix effects of benapenem and IS were 85.68%–92.04% and 83.17%–92.04%, respectively. The method was successfully applied to the preclinical pharmacokinetic (PK) studies of benapenem. We also developed a two-compartment model to characterize the PK profiles of benapenem in infected mice, which could provide a better understanding of the PK properties of benapenem.     

Establishment of a liquid chromatographic/mass spectrometry method for quantification of tetrandrine in rat plasma and its application to pharmacokinetic study

A rapid and sensitive liquid chromatography-tandem mass spectrometric method (LC/MS/MS) for the determination of tetrandrine in rat plasma has been developed, fully validated and successfully applied to pharmacokinetic study in Sprague-Dawley (SD) rats after a single oral administration. Sample preparation involves a liquid-liquid extraction with n-hexane-dichlormethane (65:35, containing 1% 2-propanol isopropyl alcohol, v/v). Tetrandrine and brodimoprim (internal standard) were well separated by LC with a Dikma C(18) column using acetonitrile-methanol-ammonium formate aqueous solution (20mM) containing 0.3% formic acid (20:30:50, v/v/v) as mobile phase. Detection was performed on a triple quadrupole mass spectrometer in multiple reaction monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved using MS/MS analysis, m/z 623.0-->381.0 and m/z 339.0-->281.0 for tetrandrine and I.S., respectively. The present method exhibited good linearity over the concentration range of 5-2,000 ng/mL for tetrandrine in rat plasma with a lower limit of quantification of 5 ng/mL. The intra- and inter-day precision were 2.0-9.2% and 4.5-9.4%, and the intra- and inter-day accuracy ranged from -7.6 to 10.3% and -6.0 to 5.3%, respectively. No endogenous compounds were found to interfere with the analysis, and tetrandrine was stable during the whole assay period. The method was successfully applied to a pharmacokinetic study after an intragastric administration (i.g.) of tetrandrine to SD rats with a single dose of 50mg/kg. The results confirm that the assay is suitable for the pharmacokinetic study of tetrandrine.     

An HPLC-MS/MS method for the quantitative determination of 4-hydroxy-anethole trithione in human plasma and its application to a pharmacokinetic study

A selective, rapid and sensitive method for the quantitation of 4-hydroxy-anethole trithione (ATX) in human plasma based on high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) was developed and validated. Paracetamol was used as the internal standard (I.S.). After liquid–liquid extraction of 500 μL plasma with ethyl acetate, ATX and the I.S. were chromatographed on an Inertsil^® ODS-3 column. The mobile phase was consisted of methanol–water (75:25, v/v) with a flow rate of 0.25 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. The calibration curve was linear over the range of 0.452–603 ng/mL (r² ≥ 0.99) with a lower limit of quantitation (LLOQ) of 0.452 ng/mL. The intra- and inter-day precision (relative standard deviation, R.S.D.) values were below 13% and the accuracy (relative error, R.E.) was from −2.7% to −7.5% at three quality control levels. The assay herein described was successfully applied to a pharmacokinetic study of anethole trithione (ATT) tablet in healthy volunteers after oral administration.     

HPLC-MS/MS法测定雷诺嗪血药浓度及其缓释制剂的药代动力学研究

目的:通过方法学的建立和确认,进行了单次给药雷诺嗪缓释片后的药动学研究,为该药临床研究及合理用药提供依据。方法:12名健康受试者,男女各半,采用三周期、3交叉(3×3)拉丁方设计,实验分别单剂量给500、1000、1500mg雷诺嗪缓释片。分别于给药前(0h)和给药后0.5、1.0、2.0、2.5、3.0、3.5、4.0、5.0、6.0、8.0、10.0、12.0、16.0、24.0、36.0、48.0h采集静脉血4mL。采用LC-MS/MS法测定血浆样品中雷诺嗪的浓度,并计算主要的药动学参数。结果:单剂量给药500、1000、1500mg雷诺嗪缓释片后Cmax分别为(742±253)、(1355±502)和(2329±890)ng/mL;AUC0-48分别为(9072±3400)、(16574±6806)和(29324±10857)ng.mL-1.h;AUC0-∞分别为(9827±3152)、(16882±6791)和(29924±10706)ng.mL-1.h;tmax分别为(5.3±1.4),(4.2±1.2)和(5.9±2.8)h;t1/2分别为(6.4±3.3),(6.4±3.5)和(6.7±4.3)h。结论:在本次实验中,Cmax和AUC与剂量成比例增加,单次给药3个剂量有很好的线性关系,所有受试者都有较好的耐受性。     

Rapid and sensitive HPLC-MS/MS method for quantitative determination of isochlorogenic acid B in rat plasma and its application in pharmacokinetic study

Asensitive LC-ESI-MS/MS method for determination of isochlorogenic acid B in rat plasma was developed and validated in the present study. Plasma samples were prepared by a simple protein precipitation with methanol containing resveratrol as internal standard (IS). The chromatographic separation was performed on a Zorbax SB-C₁₈ column (3.5 μm, 2.1 mm×100 mm, Agilent, USA) at a flow rate of 0.2 mL/min using methanol/water containing 0.1% formic acid (v/v) as mobile phase. The detectionwas performed on a triple quadrupole tandem mass spectrometer equipped with Electronic Spray Ion by selected reaction monitoring (SRM) of the transitions at m/z 515.3→352.9 for isochlorogenic acid B and m/z 227.1→143.1 for IS, respectively. The calibration curve of the method was linear over the range of 5–2500 ng/mL (r² = 0.9982). The intra- and inter-day precisions (R.S.D.%) were less than 12.46%, and the accuracy (R.E.%) was within ±5.80%. Isochlorogenic acid B was sufficiently stable under all relevant analytical conditions. The validated method was successfully applied to the plasma pharmacokinetic studies of isochlorogenic acid B in rats. It was found that isochlorogenic acid B had non-linear pharmacokinetic characteristics in rats within the dosage ranges from 5 to 20 mg/kg.     

Quantification of oltipraz using liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study in rat plasma

An assay method for the determination of oltipraz, a candidate drug for the treatment of liver fibrosis and liver cirrhosis, was developed in rat plasma using a fast-flow protein precipitation (FF-PPT) method coupled with LC-MS/MS for quantification to reduce the labor and to improve the speed of analysis. The applicability of the assay to pharmacokinetic studies was also evaluated. Oltipraz and ethyl-oltipraz, an internal standard (IS), were analyzed by multiple reaction monitoring (MRM) at m/z transitions of 227 → 193 and 241 → 174, respectively. A lower limit of quantification (LLOQ) of 20 ng/mL was observed, with a linear dynamic range from 20 to 4000 ng/mL (R > 0.997). The accuracy, precision, dilution, recovery, and stability of the assay were deemed acceptable according to FDA guidelines. Oltipraz concentrations were measured successfully in plasma samples up to 12 h post-dose in rats that had received an oral dose of 60 mg/kg. The findings indicate that the assay method is rapid and sensitive to oltipraz, showing applicability for pharmacokinetics (PK) studies of oltipraz in other small animals, including rats.     

Determination of dabigatran in dog plasma by LC-MS/MS and its application to a pharmacokinetic study of dabigatran etexilate nanosuspension

In this study, a sensitive and rapid LC-MS/MS method was developed and validated to determine dabigatran in plasma of beagle dogs after oral administration of dabigatran etexilate nanosuspension (DABE-NS). The analytes (dabigatran) and sertraline hydrochloride (internal standard, IS) were separated on a Kromasil C₁₈ column using gradient elution consisting of methanol and formate buffer at a flow rate of 0.4 mL/min in 20 min. Detection and quantitation were carried out by multiple reaction monitoring following the transitions: m/z 472.17→289.07 and 305.98→275.00 for dabigatran and IS at positive ion mode, respectively. The calibration curves were linear from 1.0 to 500.0  ng/mL for dabigatran with r  = 0.9995. The accuracy of each analyte ranged from 94.8% to 107.1%, and the precision was within 6%. Besides, this method was successfully applied in the investigation of the pharmacokinetic profile of dabigatran in beagle dogs after oral administration ofDABE-NS. The maximum concentration and the areas under curves of dabigatranfor DABE-NS were significantly higher than those of control formulation, indicating improved oral absorption.     

高效液相-质谱联用法（LC—MS／MS）测定延龄草苷血药浓度及其药物动力学研究

目的:进行延龄草苷在小鼠体内的药物动力学研究。方法:采用甲醇沉淀蛋白进行血浆样品预处理,选用人参皂苷 Rh2为内标,以 LC-MS/MS 法测定小鼠血浆中延龄草苷的含量。色谱柱为 MetaChem ODS-3(50mm×2.0mm,5μm),流动相为乙腈-水-甲酸(80:20:0.1),流速为0.2mL·min~(-1)。电喷雾离子化(ESI)方式,采用多反应监测,检测离子为正离子,分别选择 m/z 577.6→253.6amu 和 m/z 621.5→603.7amu 作为延龄草苷和内标物人参皂苷 Rh2的检测离子对。结果:延龄草苷在2.0μg·mL~(-1)～200μg·mL~(-1)范围内线性关系良好(r=0.9964)。方法的准确度范围为-3.0%～1.4%,日内精密度 RSD 范围为1.1%～3.3%,日间精密度 RSD 范围为3.2%～5.1%。小鼠尾静脉注射延龄草苷(7.6mg·kg~(-1))后,药-时数据符合二室模型,主要药物动力学参数:t_(1/2)为5.56h、K_e 为0.12h~(-1)、C_(max)为130.1μg·mL~(-1)、V_d 为4.6mL、Cl 为0.049mL·h·kg~(-1)。结论:建立的含量测定方法快速、准确,适用于延龄草苷在小鼠体内的药物动力学研究。     

Simultaneous determination of amoxicillin and ambroxol in human plasma by LC-MS/MS: validation and application to pharmacokinetic study

A rapid, simple and sensitive LC-MS/MS method was developed for simultaneous determination of amoxicillin and ambroxol in human plasma using clenbuterol as internal standard (IS). The plasma samples were subjected to a simple protein precipitation with methanol. Separation was achieved on a Lichrospher C(18) column (150 mm x 4.6mm ID, dp 5 microm) using methanol (containing 0.2% of formic acid) and water (containing 0.2% of formic acid) as a mobile phase by gradient elution at a flow rate of 1.0 mL/min. Detection was performed using electrospray ionization in positive ion multiple reaction monitoring (MRM) mode by monitoring the ion transitions from m/z 365.9-->348.9 (amoxicillin), m/z 378.9-->263.6 (ambroxol) and m/z 277.0-->203.0 (IS). Calibration curves were linear in the concentration range of 5-20,000 ng/mL for amoxicillin, and 1-200 ng/mL for ambroxol, with the intra- and inter-run precisions of <9% and the accuracies of 100+/-7%. The method has been validated and applied to pharmacokinetic studies of compound amoxicillin and ambroxol hydrochloride tablets in healthy Chinese volunteers.     

Development of a robust and sensitive LC-MS/MS method for the determination of adenine in plasma of different species and its application to in vivo studies

A simple, robust, and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed for the measurement of endogenous adenine in mouse, rat, cynomolgus monkey, and human plasma. A “surrogate analyte” strategy was adopted by employing [¹³C(U)]-adenine as the surrogate analyte. The plasma samples were processed by protein precipitation, and the extracted supernatant samples were subjected directly to LC-MS/MS analysis. The analysis was carried out in the negative ion detection mode using selected-reaction monitoring (SRM). The method achieved a lower limit of quantification (LLOQ) of 5.0 nM with a signal-to-noise ratio of 10. The intra- and inter-day assay coefficients of variation (CV) were ≤6.67% in rat plasma, and the mean recoveries and matrix effects across species and at various concentrations ranged from 88.8% to 104.2% and 86.0% to 110.8%, respectively. Using this methodology, the endogenous concentration of adenine in plasma of four species was found to range from 8.7 nM in human to 93.1 nM in cynomolgus monkey plasma. The assay was further applied to both an adenine pharmacokinetic study and a pivotal pharmacodynamic study evaluating the plasma concentration of adenine after a dose of 5′-deoxy-5′-methylthioadenosine (MTA).