Determination of two HMG-CoA reductase inhibitors, pravastatin and pitavastatin, in plasma samples using liquid chromatography-tandem mass spectrometry for pharmaceutical study

We developed a method for determining pravastatin or pitavastatin, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, in plasma using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Pravastatin, pitavastatin and the internal standard fluvastatin were extracted from plasma with solid-phase extraction columns and eluted with methanol. After drying the organic layer, the residue was reconstituted in mobile phase (acetonitrile:water, 90:10, v/v) and injected onto a reversed-phase C(18) column. The isocratic mobile phase was eluted at 0.2 mL/min. The ion transitions recorded in multiple reaction monitoring mode were m/z 423 --> 101, 420 --> 290 and 410 --> 348 for pravastatin, pitavastatin and fluvastatin, respectively. The coefficient of variation of the assay precision was less than 12.4%, the accuracy exceeded 89%. The limit of detection was 1 ng/mL for all analytes. This method was used to measure the plasma concentration of pitavastatin or pravastatin from healthy subjects after a single 4 mg oral dose of pitavastatin or 40 mg oral dose of pravastatin. This is a very simple, sensitive and accurate analytic method to determine the pharmacokinetic profiles of pitavastatin or pravastatiny.     

Simultaneous determination of udenafil and its active metabolite, DA-8164, in human plasma and urine using ultra-performance liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study

A rapid, sensitive, and simple ultra-performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) method for the determination of udenafil and its active metabolite, DA-8164, in human plasma and urine using sildenafil as an internal standard (IS) was developed and validated. Udenafil, DA-8164 and IS from a 100 microL aliquot of biological samples were extracted by protein precipitation using acetonitrile. Chromatographic separation was carried on an Acquity UPLC BEH C(18) column (50 x 2.1 mm, i.d., 1.7 microm) with an isocratic mobile phase consisting of acetonitrile and containing 0.1% formic acid (75:25, v/v) at flow rate of 0.4 mL/min, and total run time was within 1 min. Detection and quantification was performed by the mass spectrometer using multiple reaction-monitoring mode at m/z 517 --> 283 for udenafil, m/z 406 --> 364 for DA-8164 and m/z 475 --> 100 for IS. The assay was linear over a concentration range of 1-600 ng/mL with a lower limit of quantification of 1 ng/mL in both human plasma and urine. The coefficient of variation of this assay precision was less than 13.7%, and the accuracy exceeded 92.0%. This method was successfully applied for pharmacokinetic study after oral administration of udenafil 100 mg to healthy Korean male volunteers.     

Rapid and sensitive determination of donepezil in human plasma by liquid chromatography/tandem mass spectrometry: application to a pharmacokinetic study

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for the determination of donepezil in human plasma samples. Diphenhydramine was used as the internal standard. The collision-induced transition m/z 380 --> 91 was used to analyze donepezil in selected reaction monitoring mode. The signal intensity of the m/z 380 --> 91 transition was found to relate linearly with donepezil concentrations in plasma from 0.1-20.0 ng/mL. The lower limit of quantification of the LC/MS/MS method was 0.1 ng/mL. The intra- and inter-day precisions were below 10.2% and the accuracy was between -2.3% and +2.8%. The validated LC/MS/MS method was applied to a pharmacokinetic study in which healthy Chinese volunteers each received a single oral dose of 5 mg donepezil hydrochloride. The non-compartmental pharmacokinetic model was used to fit the donepezil plasma concentration-time curve. Maximum plasma concentration was 12.3 +/- 2.73 ng/mL which occurred at 3.50 +/- 1.61 h post-dosing. The apparent elimination half-life and the area under the curve were, respectively, 60.86 +/- 12.05 h and 609.3 +/- 122.2 ng . h/mL. LC/MS/MS is a rapid, sensitive and specific method for determining donepezil in human plasma samples.     

超高效液相色谱-质谱/质谱联用法测定人血浆中的辛伐他汀

建立了超高效液相色谱-质谱/质谱联用法(UPLC-MS/MS)测定人血浆中辛伐他汀的浓度。血浆样品经乙醚-正己烷-异丙醇(体积比为80∶20∶3)提取,以洛伐他汀为内标,采用ACQUITY UPLCTM BEH C18柱(50 mm×2.1 mm,1.7 μm)分离,以乙腈-10 mmol/L乙酸铵水溶液(体积比为85∶15)为流动相,流速为0.25 mL/min,通过电喷雾离子化,采用多反应监测(MRM)方式进行正离子检测。线性范围为0.051～20.4 ng/mL,日内及日间测定的相对标准偏差不高于10%,平均回收率为91.6%。方法灵敏度高,分析速度快,操作简便,适用于辛伐他汀药物动力学和生物等效性研究。     

Bioanalytical technique for determination of tasimelteon in human plasma by LC–MS/MS and its application to pharmacokinetic study in humans

A highly sensitive, specific and rapid liquid chromatography–tandem mass spectrometry technique for the quantification of tasimelteon in human plasma has been developed and validated using tasimelteon‐d₅ as internal standard. Liquid–liquid extraction technique with ethyl acetate was used for extraction of tasimelteon from the plasma. The chromatographic separation was achieved on an Agilent Zorbax, Eclipse, C₁₈ (4.6 × 50 mm, 5 μm) column using a mobile phase of acetonitrile and 0.02% formic acid buffer (85:15, v/v) with a flow rate of 0.5 mL/min. A detailed method validation was performed as per the United States Food and Drug Administration guidelines. The linear calibration curve was obtained over the concentration range 0.30–299 ng/mL. The API‐4000 liquid chromatography–tandem mass spectrometry was operated under multiple reaction monitoring mode during analysis. The validated method was successfully applied to estimate plasma concentration of tasimelteon after oral administration of a single dose of a 20 mg capsule in healthy volunteers under fasting conditions. The maximum concentration of the drug achieved in the plasma was 314 ± 147 ng/mL and the time at which this concentration was attained was 0.54 ± 0.22 h.     

Rapid and sensitive liquid chromatography tandem mass spectrometry method for the quantification of ambroxol in human plasma

A sensitive, specific and rapid high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was described and validated for the quantification of ambroxol in human plasma using enalaprilat as the internal standard (IS). Chromatographic separation was performed on a Lichrospher CN column with a mobile phase of methanol and water (containing 0.1% formic acid) (70:30, v/v). The total run time was 5.0 min for each sample. The analytes was detected by mass spectrometry with electrospray ionization source in positive selected reaction monitoring mode. The precursor-fragment ion reaction for ambroxol was m/z 378.9 --> 263.8, and for IS was m/z 349.0 --> 205.9. The linearity was established over the concentration range of 1.56-400.00 ng/mL. The inter-day and the intra-day precisions were all within 10%. A simple protein precipitation with methanol was adopted for sample preparation. The extraction recoveries of ambroxol and IS were higher than 90.80%. The validated method was successfully applied in pharmacokinetic study after oral administration of 90 mg ambroxol to 24 healthy volunteers.     

Development and validation of a liquid chromatographic/tandem mass spectrometric method for the determination of sertraline in human plasma

A sensitive and rapid liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of sertraline in human plasma. The analyte and internal standard (IS, diphenhydramine) were extracted with 3 mL of diethyl ether/dichloromethane (2:1, v/v) from 0.25 mL plasma, then separated on a Zorbax Eclipse XDB C18 column using methanol/water/formic acid (75:25:0.1, v/v/v) as the mobile phase. The triple quadrupole mass spectrometry was applied via an atmospheric pressure chemical ionization (APCI) source for detection. The fragmentation pattern of the protonated sertraline was elucidated with the aid of product mass spectra of isotopologous peaks. Quantification was performed using selected reaction monitoring of the transitions of m/z 306 --> 159 for sertraline and m/z 256 --> 167 for the IS. The method was linear over the concentration range of 0.10-100 ng/mL. The intra-day and inter-day precisions, expressed by relative standard deviation, were both less than 6.7%. Assay accuracies were within +/-6.9% as terms of relative error. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.10 ng/mL with a precision of 8.3% and an accuracy of 9.6%. The validated method has been successfully applied for the pharmacokinetic study and bioequivalence evaluation of sertraline in 18 healthy volunteers after a single oral administration of 50 mg sertraline hydrochloride tablets.     

Validated LC-MS/MS method for quantification of gabapentin in human plasma: application to pharmacokinetic and bioequivalence studies in Korean volunteers

A sensitive validated liquid chromatography-tandem mass spectrometric method (LC-MS/MS) for gabapentin (GB) in human plasma has been developed and applied to pharmacokinetic (PK) and bioequivalence (BE) studies in human. In a randomized crossover design with a 1-week period, each subject received a 300 mg GB capsule. The procedure involves a simple protein precipitation with acetonitrile and separated by LC with a Gemini C(18) column using acetonitrile-10 mm ammonium acetate (20:80, v/v, pH 3.2) as mobile phase. The GB and internal standard [(S)-(+)-alpha-aminocyclohexanepropionic acid hydrate] were analyzed using an LC-API 2000 MS/MS in multiple reaction monitoring mode. The ionization was optimized using ESI(+) and selectivity was achieved using MS/MS analysis, m/z 172.0 --> 154.0 and m/z 172.0 --> 126.0 for GB and IS, respectively. The assay exhibited good linearity over a working range of 20-5000 ng/mL for GB in human plasma with a lower limit of quantitation of 20 ng/mL. No endogenous compounds were found to interfere with the analysis. The accuracy and precision were shown for concentrations over the standard ranges. This method was successfully applied for the PK and BE studies by analysis of blood samples taken up to 36 h after an oral dose of 300 mg of GB in 24 healthy volunteers.     

Determination of donepezil hydrochloride (E2020) in plasma by liquid chromatography-mass spectrometry and its application to pharmacokinetic studies in healthy, young, Chinese subjects

A sensitive, simple, and specific liquid chromatographic method coupled with electrospray ionization-mass spectrometry for the determination of donepezil in plasma is developed, and its pharmacokinetics in healthy, male, Chinese is studied. Using loratadine as the internal standard, after extraction of the alkalized plasma by isopropyl alcohol-n-hexane (3:97, v/v), solutes are separated on a C(18) column with a mobile phase of methanol-acetate buffer (pH 4.0) (80:20, v/v). Detection is performed with a time-of-flight mass spectrometer equipped with an electrospray ionization source operated in the positive-ionization mode. Quantitation of E2020 is accomplished by computing the peak area ratio (donepezil [M+H](+) m/z 380-loratadine [M+H](+) m/z 383) and comparing them with the calibration curve (r = 0.9998). The linear calibration curve is obtained in the concentration range 0.1-15 ng/mL. The limit of quantitation is 0.1 ng/mL. The mean recovery of E2020 from human plasma is 99.4% +/- 6.3% (ranging 93.4-102.6%). The inter- and intraday relative standard deviation is less than 15%. After an oral administration of 5 mg E2020 to 20 healthy Chinese volunteers, the main pharmacokinetic parameters of E2020 are as follow: T(max), 3.10 +/- 0.55 h; t((1/2)), 65.7 +/- 12.8 h; C(max), 10.1 +/- 2.02 ng/mL; MRT, 89.4 +/- 13.4 h; and CL/F, 9.9 +/- 4.3 L/h.     

Rapid and sensitive determination of udenafil in plasma by LC-MS/MS for intranasal pharmacokinetic study in rats

A rapid and sensitive analytical method for udenafil in rat plasma was developed and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This chromatographic procedure was then applied to the in vivo pharmacokinetic studies in rats for determining the advantages of intranasal administration of the drug over oral administration. Using liquid-liquid extraction (LLE), udenafil and the internal standard (IS) sildenafil were extracted with dichloromethane from 100 μl of plasma samples. Chromatographic separation was performed using Pursuit XRS C?? column (50 mm × 2.1 mm, i.d., 3 μm, Varian Inc., CA, U.S.A.) with an isocratic mobile phase consisting of acetonitrile and 10 mM ammonium acetate (90 : 10, v/v) at a flow rate of 0.2 ml/min over a total run time of 2.5 min. Detection and quantification was performed by mass spectrometry using the multiple reaction-monitoring mode at m/z 517.4→283.1 for udenafil and m/z 475.3→100.0 for IS. Results showed that the developed method was sensitive and specific for udenafil. Linearity was obtained in the range of 0.5-1000 ng/ml. The coefficient of variation of both intra- and inter-day validation were below 11.6% and the intra- and inter-day accuracy ranged from 91.5 to 109.9%. Udenafil concentration was successfully measured from plasma after intranasal as well as after intravenous or oral administration at clinical dose (1.67 mg/kg) in rats. Moreover, the T(max) values obtained from pharmacokinetic studies suggested that administration of udenafil intranasally could be more effective than by the oral route.     

Sensitive and rapid liquid chromatography/tandem mass spectrometry assay for the quantification of amlodipine in human plasma

A simple, sensitive and rapid high-performance liquid chromatography/electrospray ionization tandem mass spectrometry method was developed and validated for the assay of amlodipine in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase C(18) column and analyzed by MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 409/238 for amlodipine and m/z 409/228 for the IS. The assay exhibited a linear dynamic range of 50-10,000 pg/mL for amlodipine in human plasma. The lower limit of quantification was 50 pg/mL with a relative standard deviation of less than 8%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The average absolute recoveries of amlodipine and the IS from spiked plasma samples were 74.7 +/- 4.6 and 72.1 +/- 2.0%, respectively. A run time of 1.5 min for each sample made it possible to analyze 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. The observed maximum plasma concentration (Cmax) of amlodipine (2.5 mg oral dose) was 1425 pg/mL, time to observed maximum plasma concentration (Tmax) was 8.1 h and elimination half-life (T(1/2)) was 50.1 h.     

Development of a rapid and sensitive liquid chromatography/tandem mass spectrometry method for the determination of 1,2-[bis(1,2-benzisoselenazolone-3(2H)-ketone)]-ethane (BBSKE), a novel anti-cancer agent in rat plasma

A rapid and sensitive liquid chromatography/electrospray ionization tandem mass spectrometric (LC/ESI-MS/MS) method has been developed to determine 1, 2-[bis(1,2-benzisoselenazolone-3(2H)-ketone)]-ethane (BBSKE), a novel antineoplastic agent, in rat plasma. The analytes were separated on a C18 column with a mobile phase of methanol-water (75:25, v/v) and detected using a triple-quadrupole mass spectrometer in positive mode with the selective reaction monitoring. The characteristic ion dissociation transitions were m/z 603.0 --> 448.9 for derivatized BBSKE and m/z 631.0 --> 476.8 for derivatized internal standard. The assay was linear over a range of 1-1000 ng/mL with a lower limit of quantification of 1 ng/mL. Intra- and inter-day precisions were less than 9.6 and 5.0%, respectively, and the accuracy ranged from -5.2 to 4.0%. The validated method was successfully applied to the characterization of pharmacokinetic profile of BBSKE after oral administration in rats. Cop     

Determination of roxatidine in human plasma by liquid chromatography/electrospray mass spectrometry and application to a clinical pharmacokinetic study

A rapid and sensitive liquid chromatography/mass spectrometry (LC/MS) method was developed and validated for the determination of roxatidine in human plasma. Roxatidine was extracted by single liquid-liquid extraction with tert-butyl methyl ether, and the chromatographic separation was performed on a C8 column. The total analytical run time was relatively short (5 min), and the limit of assay quantification was 2 ng/mL using 0.1 mL of human plasma. Roxatidine and the internal standard, propranolol, were monitored in selected ion monitoring (SIM) mode at m/z 307.3 and 260.3, respectively. The standard curve was linear over a concentration range from 2-500 ng/mL, and the correlation coefficients were >0.999. The mean intra- and inter-day assay accuracy ranged from 103.4-108.8% and 102.3-110.0%, respectively, and the mean intra- and inter-day precision was between 3.3-8.8% and 5.3-6.2%, respectively. The developed assay method was successfully applied to a pharmacokinetic study in human volunteers after oral administration of roxatidine acetate hydrochloride at a dose of 75 mg.     

Liquid chromatographic-electrospray tandem mass spectrometric determination of clarithromycin in human plasma

A rapid, sensitive and specific LC-MS-MS method has been developed for the determination of clarithromycin (CLA) in human plasma using roxithromycin (ROX) as the internal standard. Samples were prepared via liquid-liquid extraction with methyl tert-butyl ether (MTBE) and chromatographed on a Supelco RP(18) (4.6 x 50 mm, 3 microm particle size) column with a mobile phase consisting of acetonitrile:methanol:60 mM (pH 3.5) ammonium acetate buffer (32.5:32.5:35) at a constant flow rate of 0.8 mL/min. The run time was 3 min with retention times of approximately 1.65 and 1.70 min for CLA and ROX, respectively. Detection was performed on a PE Sciex API 365 mass spectrometer equipped with a turboionspray ionization source in multiple reaction monitoring (MRM) mode. The MRM pairs were m/z 748.5 --> m/z 158.2 for CLA and m/z 837.7 --> m/z 679.3 for ROX, respectively, with dwell times of 200 ms for each transition. The validated calibration curve range was 5.00-5000 ng/mL, based on 0.100 mL plasma sample volume with signal-to-noise ratio (S/N) greater than 60 for CLA at the lower limit of quantification level (5.00 ng/mL). The correlation coefficients (r(2)) of the calibration curves were better than or equal to 0.996. The inter-day (n = 18) precision and accuracy of the quality control (QC) samples were less than 3.58% RSD (relative standard deviation) and -10.8% bias, respectively. The intra-day (n = 6) precision and accuracy of the quality control samples were less than 5.0 and 12.6%, respectively. There was no significant deviation from the nominal values after a 10-fold dilution of high concentration QC samples using blank matrix. The QC samples were stable when left on the bench for 24 h or after three freeze-thaw cycles. The processed samples were also stable in HPLC autosampler at 10C for over 72 h. No matrix ionization suppression was observed when extracted blank matrix or reconstitution solvent was injected onto the system with post-column infusion of clarithromycin and roxithromycin. No carryover was observed when an extracted blank plasma sample was injected immediately after a 5000 ng/mL ULOQ (the upper limit of quantification) standard. The mean recovery was 81.5 and 78.3%, respectively, for clarithromycin and internal standard.     

Development and validation of an LC–MS/MS method for the determination of hinokiflavone in rat plasma and its application to a pharmacokinetic study

Hinokiflavone has drawn a lot of attention for its multiple biological activities. In this study, a sensitive and selective method for determination of hinokiflavone in rat plasma was developed for the first time, using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Amentoflavone was used as an internal standard. Separation was achieved on a Hypersil Gold C₁₈ column with isocratic elution using methanol–water (65:35, v /v) as mobile phase at a flow rate of 0.3 mL/min. A triple quadrupole mass spectrometer operating in the negative electrospray mode with selected reaction monitoring was used to detect the transitions of m/z 537 → 284 for hinokiflavone and m/z 537 → 375 for IS. The LOQ was 0.9 ng/mL with a linear range of 0.9–1000 ng/mL. The intra‐ and inter‐day accuracy (RE%) ranged from −3.75 to 6.91% and from −9.20 to 2.51% and the intra‐ and inter‐day precision (RSD) was between 0.32–14.11 and 2.85–10.04%. The validated assay was successfully applied to a pharmacokinetic study of hinokiflavone in rats. The half‐life of drug elimination at the terminal phase was 6.10 ± 1.86 h, and the area under the plasma concentration‐time curve from time zero to the time of last measurable concentration and to infinity values obtained were 2394.42 ± 466.86 and 2541.93 ± 529.85 h ng/mL, respectively.     

Determination of sodium cromoglycate in human plasma by liquid chromatography with tandem mass

A sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of sodium cromoglycate (SCG) in human plasma after a nasal dose of 10.4 mg sodium cromoglycate nasal spray, using pravastatin sodium as the internal standard. The method was validated over a linear range of 0.300-20.0 ng/mL. SCG and I.S. were extracted from 1.0 mL of heparinized plasma by C(18) solid-phase extraction cartridges using methanol as eluting solvent. The dried residue was reconstituted with 100 microL of mobile phase, and 10 microL was injected onto the LC-MS/MS system. Chromatographic separation was achieved on a C(18) column (250 x 4.6 mm i.d., 5 microm particle size) with a mobile phase of methanol-acetonitrile-water (containing 2 mmol/L ammonium acetate; 42.5:42.5:15, v/v/v) at a flow rate of 0.4 mL/min. The analytes were detected with a triple quad LC-MS/MS using ESI with positive ionization. Ions monitored in the multiple reaction monitoring mode were m/z 469.0 (precursor ion) to m/z 245.0 (product ion) for SCG and m/z 447.2 (precursor ion) to m/z327.1 (product ion) for pravastatin sodium (internal standard) The average recovery of SCG from human plasma was 94.88% and the lower limit of quantitation was 0.3 ng/mL. Results from a 3-day validation study demonstrated excellent precision and accuracy across the calibration range of 0.3-20 ng/mL. The method was successfully applied to the pharmacokinetic study of SCG in healthy Chinese volunteers. Copyright (c) 2008 John Wiley & Sons, Ltd.     

A high-performance liquid chromatography/tandem mass spectrometry method for the determination of artemisinin in rat plasma

Artemisinin is a widely used antimalarial drug. To evaluate the pharmacokinetics of artemisinin in rats, a sensitive and specific liquid chromatography/tandem mass spectrometric (LC/MS/MS) method was developed and validated for the determination of artemisinin in rat plasma. For detection, a Sciex API 4000 LC/MS/MS instrument with an electrospray ionization (ESI) TurboIonSpray inlet in the positive ion multiple reaction monitoring (MRM) mode was used to monitor precursor ([M+NH4]+) --> product ions of m/z 300.4 --> 209.4 for artemisinin and m/z 316.4 --> 163.4 for artemether, the internal standard (IS). The plasma samples were pretreated by a simple liquid-liquid extraction with ether. The standard curve was linear (r > 0.99) over the artemisinin concentration range of 1.0-200.0 ng/mL in plasma. The method had a lower limit of quantification of 1.0 ng/mL for artemisinin in 100 microL of plasma, which offered a satisfactory sensitivity for the determination of artemisinin. The intra- and inter-day precisions were measured to be within +/-5.3% and accuracy between -2.6% and 1.2% for all quality control samples, lower limit of quantification and upper limit of quantification samples. The extraction recoveries of artemisinin and the IS were 95.4 +/- 4.5% and 92.8 +/- 3.9%, respectively. This present method was successfully applied to the characterization of the pharmacokinetic profile of artemisinin in rats after oral administration.     

Determination of aranidipine and its active metabolite in human plasma by liquid chromatography/negative electrospray ionization tandem mass spectrometry

A simple, sensitive and rapid high-performance liquid chromatography/negative electrospray ionization tandem mass spectrometry method was developed and validated for the assay of aranidipine (AR) and its active metabolite (AR-M) in human plasma. Following a liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reversed-phase column and analyzed by mass spectrometry in the multiple reaction monitoring mode using the respective [M-H]- ions, m/z 387.0 --> 164.0 for AR, m/z 389.1 --> 208.1 for AR-M and m/z 359.0 --> 121.8 for the internal standard. The assay exhibited a linear dynamic range of 0.02-10 ng x mL(-1) for AR and 0.2-100 ng x mL(-1) for AR-M in human plasma. The limits of quantitation were 0.02 ng x mL(-1) for AR and 0.2 ng x mL(-1) for AR-M. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.8 min for each sample exhibited its high-throughout analysis ability. The validated method can be applied to analyze human plasma samples for pharmacokinetic studies.     

A sensitive method for determination of salvianolic acid A in rat plasma using liquid chromatography/tandem mass spectrometry

Salvianolic acid A (SAA), a major effective constituent of Salvia miltiorrhizas, is widely used in traditional Chinese medicine. A sensitive rapid analytical method was established and validated for SAA in rat plasma, which was further applied to assess the pharmacokinetics of SAA in rats receiving a single oral dose of SAA. The method used liquid chromatography tandem mass spectrometry in multiple reaction monitoring mode with chloramphenicol as the internal standard. A simple liquid-liquid extraction based on ethyl acetate was employed. The combination of a simple sample cleanup and short chromatographic run time (3 min) increased the throughput of the method substantially. The method was validated over the range 1.4-1000 ng/mL with a correlation coefficient >0.99. The lower limit of quantification was 1.4 ng/mL for SAA in plasma. Intra- and inter-day accuracies for SAA were 95-113 and 98-107%, and the inter-day precision was less than 12%. This method is more sensitive and faster than previous methods. After a single oral dose of 100 mg/kg of SAA, the mean peak plasma concentration (Cmax) of SAA was 318 ng/mL at 0.5 h, the area under the plasma concentration-time curve (AUC0-12 h) was 698 +/- 129 ng.h/mL, and the elimination half-life (T1/2) was 3.29 h.     

LC–MS/MS method for simultaneous determination of ramelteon and its metabolite M‐II in human plasma: Application to a clinical pharmacokinetic study in healthy Chinese volunteers

A sensitive liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of ramelteon and its active metabolite M‐II in human plasma. After extraction from 200 μL of plasma by protein precipitation, the analytes and internal standard (IS) diazepam were separated on a Hedera ODS‐2 (5 μm, 150 × 2.1 mm) column with a mobile phase consisted of methanol–0.1% formic acid in 10 mm ammonium acetate solution (85:15, v/v) delivered at a flow rate of 0.5 mL/min. Mass spectrometric detection was operated in positive multiple reaction monitoring mode. The calibration curves were linear over the concentration range of 0.0500–30.0 ng/mL for ramelteon and 1.00–250 ng/mL for M‐II, respectively. This method was successfully applied to a clinical pharmacokinetic study in healthy Chinese volunteers after a single oral administration of ramelteon. The maximum plasma concentration (C_max), the time to the C_max and the elimination half‐life for ramelteon were 4.50 ± 4.64ng/mL, 0.8 ± 0.4h and 1.0 ± 0.9 h, respectively, and for M‐II were 136 ± 36 ng/mL, 1.1 ± 0.5 h, 2.1 ± 0.4 h, respectively.