M+4 stable isotope labeling of levovirin and M+7 and carbon‐14 labeling of levovirin valinate pro‐drug

[M+4]‐labeled levovirin 5 (231 mg) was synthesized as an MS reference compound from [M+4] triazole ester 2 . [M+7]‐labeled levovirin valinate 6 (127 mg) was synthesized as a comparison MS reference compound from [M+6] triazole ester 3 . [¹⁴C]‐Levovirin 7 and [¹⁴C]‐levovirin valinate 8 were synthesized to support metabolism studies. The synthesis of 7 was accomplished in 33% overall yield (35.4 mCi, 57 mCi/mmol) from Ba¹⁴CO₃ and 8 was synthesized in 41% yield (12.5 mCi, 57 mCi/mmol) from 7 . An efficient metallation/carbonation reaction was developed to synthesize [¹⁴C]‐triazole ester 4 . Copyright © 2006 John Wiley & Sons, Ltd.     

LC-MS/MS method for simultaneous determination of viramidine and ribavirin levels in monkey red blood cells

A high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed for the simultaneous determinations of total viramidine (viramidine, viramidine monophosphate, viramidine diphosphate, and viramidine triphosphate) and total ribavirin (ribavirin, ribavirin monophosphate, ribavirin diphosphate, and ribavirin triphosphate) in monkey red blood cells (RBC). The method involves the addition of internal standards and perchloric acid, conversion of viramidine or ribavirin phosphorylated metabolites to viramidine or ribavirin, purification with an aminopropyl (NH(2)) solid phase extraction (SPE) cartridge, and LC-MS/MS analysis. The MS/MS is selected to monitor m/z 245-->113, 250-->113, 244-->112, and 249-->112 for ribavirin, [(13)C]ribavirin, viramidine, and [(13)C]viramidine, respectively, using positive electrospray ionization. The calibration curves are linear over a concentration range of 100-10,000 ng/mL (0.412-41.2 microM) with a lower limit of quantification (LLOQ) of 100 ng/mL for both compounds. Mean inter-assay recoveries for ribavirin are 101%, 98.9%, and 96.0%, with coefficient of variance (%CV) values between 1.95 and 4.50% for 100, 1000, and 10,000 ng/mL quality control (QC) samples, respectively. Mean inter-assay recoveries for viramidine are 96.3%, 101%, and 102%, with coefficient of variation (%CV) values between 3.61 and 7.22%, for 100, 1000, and 10,000 ng/mL QC samples, respectively. Over-curve dilution QC at 400 microg/mL (1639 microM) for both viramidine and ribavirin are used to ensure the dilution accuracy (25 X dilutions) for monkey samples. The method has been used to simultaneously determine the total concentrations of ribavirin and viramidine in monkey RBC following 5, 15, and 36 weeks dosing of viramidine or ribavirin (60 mg/kg). The concentrations of total ribavirin following ribavirin dosing are 1242 microM at week 5, 1257 microM at week 15, and 1146 microM at week 36. The concentrations of total ribavirin following viramidine dosing are 634 microM at week 5, 716 microM at week 15, and 683 microM at week 36. Only small amounts of viramidine are detected in RBC following viramidine dosing, 7.80 microM at week 5, 6.63 microM at week 15, and 10.4 microM at week 36. The results suggest that ribavirin levels in RBC were at steady state at week 5 of ribavirin or viramidine dosing. At steady state, ribavirin levels in RBC are approximately 2x after ribavirin dosing than viramidine dosing. The relatively small percentage of viramidine in RBC suggests that viramidine either poorly penetrated into RBC or was extensively converted to ribavirin following entry into RBC.     

Single- and multiple-dose pharmacokinetics of levovirin valinate hydrochloride (R1518) in healthy volunteers

R1518 is a valine ester prodrug of levovirin as an investigational new drug for the treatment of hepatitis C virus. Two phase 1, single- and multiple-dose studies were conducted to investigate the pharmacokinetics of R1518 in healthy volunteers. After oral dosing, R1518 was rapidly and exclusively converted to levovirin. Levovirin plasma concentrations peaked at 2 hours, with T(1/2) ranging from 6 to 8 hours. The T(1/2) of R1518 was less than 1 hour, with relative exposures (R1518/levovirin) less than 6%. A high-fat meal did not affect the pharmacokinetics. The female groups in both studies had higher plasma levels than males did due to age and renal function difference. An accumulation ratio of 1.3 to 1.5 was observed with the twice-daily regimen. About 75% to 90% of the levovirin equivalent dose was recovered in urine. Increase in exposure was slightly disproportionate to increase in dose. Significantly improved oral absorption of levovirin was achieved following administration of R1518.     

A sensitive and specific method for the determination of total ribavirin in monkey liver by high-performance liquid chromatography with tandem mass spectrometry

A sensitive and specific method using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of total ribavirin in monkey liver is developed and validated. In this method, ribavirin and its phosphorylated metabolites are extracted with perchloric acid. The metabolites are converted to ribavirin using acid phosphatase and further purified using a NH2 solid-phase extraction (SPE) cartridge prior to LC-MS/MS analysis. [13C]Ribavirin is added with the extraction solution as an internal standard to obtain better accuracy and precision of the analysis. The MS/MS was selected to monitor 245-->113 and 250-->113 transitions using positive electrospray ionization for ribavirin and [(13)C]ribavirin. The calibration curve is linear over a concentration of 1.0-100 microg/g with a limit of quantitation (LOQ) of 1.0 microg/g. Mean inter-assay accuracy for QC at 1.0, 10 and 100 microg/g are 108, 99.7 and 99.7%, respectively. Mean inter-assay precision (CV) for QC at 1.0, 10 and 100 microg/g are 5.34, 5.24 and 4.59%, respectively. Extractability of total ribavirin from liver has been confirmed with liver obtained from monkey dosed with [14C]ribavirin. The method has been proven to be useful in the determination of total ribavirin concentration in liver from monkeys in mass balance study (10 mg/kg) and in 28 days toxicology study (300 mg/kg/day). It is also used to determine the total ribavirin concentration in human livers from hepatitis C patients received dose of 600 mg ribavirin twice daily.     

Development of a sensitive bioanalytical method for determination of PNU-83757 in rat,monkey and human plasma: from LC-UV to LC-MS/MS

To support pre-clinical pharmacokinetic/toxicokinetic (PK/TK) evaluation, a sensitive bioanalytical method for determination of N-cyano-N'-(tert-pentyl)-N"-(3-pyridinyl) guanidine (PNU-83757), in rat and monkey plasma was required. Although the UV response of PNU-83757 was quite decent and the extracts using solid phase extraction (SPE) were very selective and concentrated, the best limit of quantitation (LOQ) achieved was 0.4 ng ml(-1) using 0.5 ml plasma for extraction and 2 ng ml(-1) using 0.1 ml plasma for extraction, which was insufficient for PK/TK evaluation at lower doses. When using liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometric detection (LC-APCI-MS/MS, positive ions) and SPE, a LOQ of 0.045 ng ml(-1) for PNU-83757 was reached. Quantitation was accomplished using the precursor --> product ion combinations of m/z 232 --> 162 for PNU-83757 and m/z 236 --> 166 for the internal standard, [2H(4)]PNU-83757, in the multiple reaction monitoring mode. This method has been successfully utilized for PK/TK evaluation in pre-clinical studies and proved to have sufficient sensitivity to determine plasma concentrations for a dose level as low as 1 microg kg(-1) day(-1) in the rat and monkey. Further improvement of this method by using electrospray mass spectrometric detection (LC-ESI-MS/MS, positive ions) and automated membrane SPE, gave an LOQ of 0.008 ng ml(-1), and allowed analysis of large numbers of samples to support clinical PK studies in microg dose levels.     

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.     

Determination of loratadine and its active metabolite in human plasma by high-performance liquid chromatography with mass spectrometry detection

A new sensitive and selective liquid chromatography coupled with mass spectrometry (LC/MS/MS) method for quantification of loratadine (LOR) and its active metabolite descarboethoxyloratadine (DSL) in human plasma was validated. After addition of the internal standard, metoclopramide, the human plasma samples (0.3 ml) were precipitated using acetonitrile (0.75 ml) and the centrifuged supernatants were partially evaporated under nitrogen at 37 degrees C at approximately 0.3 ml volume. The LOR, DSL and internal standard were separated on a reversed phase column (Zorbax SB-C18, 100 mmx3.0 mm i.d., 3.5 microm) under isocratic conditions using a mobile phase of an 8:92(v/v) mixture of acetonitrile and 0.4% (v/v) formic acid in water. The flow rate was 1 ml/min and the column temperature 45 degrees C. The detection of LOR, DSL and internal standard was in MRM mode using an ion trap mass spectrometer with electrospray positive ionisation. The ion transitions were monitored as follows: 383-->337 for LOR, 311-->(259+294+282) for DSL and 300-->226.8 for internal standard. Calibration curves were generated over the range of 0.52-52.3 ng/ml for both LOR and DSL with values for coefficient of determination greater than 0.994 by using a weighted (1/y) quadratic regression. The lower limits of quantification were established at 0.52 ng/ml LOR and DSL, respectively, with an accuracy and precision less than 20%. Both analytes demonstrated good short-term, long-term, post-preparative and freeze-thaw stability. Besides its simplicity, the sample treatment allows obtaining a very good recovery of both analytes, around 100%. The validated LC/MS/MS method has been applied to a pharmacokinetic study of loratadine tablets on healthy volunteers.     

Pharmacokinetic study of the novel, synthetic trioxane antimalarial compound 97-78 in rats using an LC-MS/MS method for quantification

The present study has been designed to investigate the pharmacokinetic parameters of the novel trioxane antimalarial 97-78 (US Patent 6316493 B1, 2001) in male and female rats after single oral and intravenous administration. The pharmacokinetic profile of 97-78 was investigated in the form of its completely converted metabolite 97-63 after dose administration. Quantification of metabolite 97-63 in rat plasma was achieved using a simple and rapid LC-MS/MS method. The LC-MS/MS method has been validated in terms of accuracy, precision, sensitivity and recovery for metabolite 97-63 in rat plasma. The intra- and interday accuracy (% bias) and precision (% RSD) values of the assay were less than 10% for metabolite 97-63. The chromatographic run time was 4.0 min and the weighted (1/x2) calibration curves were linear over the range 1.56-200 ng/ml. This method was successfully applied for analysis of pharmacokinetic study samples. Maximum plasma concentrations of 97-63 at 47 mg/kg oral administration in male and female rats were 1986.6 ng/ml and 4086.7 ng/ml at time (Tmax) 0.92 h and 0.58 h, respectively. The area under the curve (AUC(0-infinity)), elimination half-life (t(1/2) beta) and mean residence time (MRT) were 4669.98 ng x h/ml, 2.8 h and 4.2 h in male and 11786.0 ng x h/ml, 4.52 h and 4.32 h in female rats respectively. After single oral and intravenous administration of 97-78 to male and female rats significant differences were observed in pharmacokinetic parameters (AUC and t (1/2) beta) for metabolite 97-63.     

Sample preparation and determination of gabapentin in venous and capillary blood using liquid chromatography-tandem mass spectrometry

An analytical method for the determination of gabapentin in serum obtained from venous blood samples has been developed using high-performance liquid chromatography (HPLC)-tandem mass spectrometry. In addition, a comparative study between capillary plasma samples and venous serum samples was carried out. This demonstrates the potential for the use of the described analytical system using very small amounts of blood. As internal standard (S)-(+)-alpha-amino-cyclohexane-propionic acid hydrate was used. Gabapentin and the internal standard are structural isomers, but have different m/z values for the fragments after collision induced dissolution. Gabapentin has 172-->154 and 172-->136 transitions and amino-cyclohexane-propionic acid hydrate has a 172-->126 transition which can be detected in tandem MS. Analysis of gabapentin was carried out on a C8 HPLC column using an isocratic mobile phase consisting of ammonium acetate (pH 3.0; 5mM)-methanol (96:4, v/v). The analytical method was validated for venous serum samples. Limit of detection was 1.6ng/ml and lower limit of quantification was 7.5ng/ml. R.S.D. values and bias values were within the range of acceptance for all concentration levels. The method developed for venous serum samples is being used in a gabapentin monitoring study using population pharmacokinetic modeling.     

A fast and sensitive liquid chromatographic-tandem mass spectrometric method for assay of lorazepam and application to pharmacokinetic analysis

A fast and sensitive method of coupled high-performance liquid chromatography-electrospray tandem mass spectrometry for the assay of lorazepam in human plasma was developed. Plasma samples were simply treated with acetonitrile to precipitate and remove proteins and the isolated supernatants were directly injected into the HPLC/MS/MS system. Chromatographic separation was performed on a Zorbax C(18) (100 x 2.1 mm I.D.) column with a 65:35 (v/v) mixed solution of acetonitrile and 10mM aqueous formic acid being used as mobile phase. With diazepam as an internal standard, quantification was performed by selected reaction ion monitoring of the transitions of m/z 321--> m/z 275 for lorazepam and m/z 285--> m/z 193 for the internal standard. The assay was validated in the concentration range of 0.71-71.3 ng/ml in human plasma. A detection limit of 0.10 ng/ml for lorazepam was achieved, and inter- and intra-run precisions of better than 4.4% (R.S.D.) were observed. The developed method has been successfully applied for pharmacokinetic study of the drug in man.     

Determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in monkey and dog plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

A specific and simultaneous assay of morphine, morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G) in monkey and dog plasma has been developed. These methods are based on rapid isolation using solid phase extraction cartridge, and high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-tandem mass spectrometric (MSMS) detection. Analytes were separated on a semi-micro ODS column in acetonitrile-formic (or acetic) acid mixed solution. The selected reaction monitoring for assay in monkey and dog plasma, as precursor-->product ion combinations of m/z 286-->286 for morphine, m/z 462-->286 for glucuronides and m/z 312-->312 for internal standard (IS, nalorphine) were used. The linearity of morphine, M-3-G and M-6-G was confirmed in the concentration range of 0.5-50, 25-2500, 2.5-250 ng/ml in monkey plasma, 0.5-100, 25-5000, 2.5-500 ng/ml in dog plasma, respectively. The precision of this assay method, expressed as CV, was less than 15% over the entire concentration range with adequate assay accuracy. Therefore, the HPLC-ESI-MSMS method is useful for the determination of morphine, M-3-G and M-6-G with sufficient sensitivity and specificity in pharmacokinetic studies.     

Development and validation of a sensitive LC-MS/MS method for the determination of adefovir in human serum and urine

A sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of adefovir (PMEA) in human serum and urine. The analyte was separated on a Diamonsil C(18) column (250 mm x 4.6 mm i.d., 5 microm particle size) by isocratic elution with methanol-water-formic acid (20:80:0.1, v/v/v) at a flow rate of 0.6 ml/min, and analyzed by mass spectrometry in multiple reaction-monitoring mode. The precursor-to-product ion transitions of m/z 274-->162 and m/z 226-->135 were used to measure and quantify the analyte and internal standard (I.S.), respectively. The weighted (1/x(2)) calibration curve was linear over serum concentration range 1.25-160.00 ng/ml and urine concentration range 0.05-8.00 microg/ml, with a correlation coefficient (r) of 0.9992 and 0.9978, respectively. The lower limit of quantification in human serum was 1.25 ng/ml. The inter- and intra-day precisions (R.S.D.%) in both serum and urine were lower than 8.64%, the mean method accuracies and recoveries from spiked serum samples at three concentrations ranged from 96.3 to 102.0% and 56.5 to 59.3%, respectively. The serum extract was stable when stored for 24h. The developed method was successfully applied to determine PMEA in human serum and urine, and proved suitable to clinical pharmacokinetic study.     

电子轰击离子化气相质谱法测定人类血浆中的丙卡特罗(英文)

目的:建立一种简便灵敏的气相质谱法用于测定丙卡特罗的血药浓度。方法:采用电子轰击离子化气相质谱法,以丙咪嗪做内标,样品采用液-液萃取、衍生化处理,分离柱为毛细管柱,进样器和接口温度分别为280℃和250℃,载气(氦气)流速为0.8 mL·min~(-1),进样口选择脉冲不分流模式,离子源和四极杆的温度分别为230℃和150℃。结果:测定方法的检测限为5 ng·L~(-1);线性范围为10-10000 ng·L~(-1);日内(n=5)和日间(n=5)变异系数均小于10％,平均回收率为99.1％±1.3％。结论:本方法灵敏、简便,可用于丙卡特罗的药代动力学研究。     

HPLC-UV method for assaying 99/357, a synthetic trioxane antimalarial derivative in rat and rabbit serum

In the present study an accurate and precise HPLC-UV assay method in rat and rabbit serum has been developed and validated for determination of 99/357--a new synthetic analogue of artemisinin developed by Central Drug Research Institute (CDRI), of the class of trioxane derivative. Separation was achieved using a C-18 reversed phase column with a mobile phase comprising of acetonitrile and deionized water (80:20%, v/v) using a UV detector, set at a wavelength of 266 nm. The method, applicable to 200 microl serum, involved double extraction of the samples with 20% isopropyl alcohol (IPA) in n-hexane. The recovery of 99/357 in the two matrices was >90%. The method was sensitive with a limit of quantitation of 25 ng/ml in both rat and rabbit matrices. Precision and accuracy were within the acceptable limits, as indicated by relative standard deviation (accuracy) varying from -12.7 to 5.7% and bias (precision) values ranging from 0.6 to 11.8%. Moreover, 99/357 was stable in serum up to 30 days of storage at -60 degrees C and after being subjected to three freeze/thaw cycles. The method will be applied to perform pharmacokinetic studies of 99/357.     

Determination of aplidin, a marine-derived anticancer drug, in human plasma, whole blood and urine by liquid chromatography with electrospray ionisation tandem mass spectrometric detection

A sensitive and highly specific liquid chromatographic method with electrospray ionisation tandem mass spectrometric detection (LC-ESI-MS/MS) is reported for the determination in human plasma, whole blood and urine of Aplidin (APL), a novel depsipeptide derived from the tunicate Aplidium albicans with a potent cytotoxic activity under investigation in clinical studies. Didemnin B was used as internal standard and, after protein precipitation with acetonitrile and liquid-liquid extraction with chloroform, APL was separated by liquid chromatography using a reversed-phase C18 column and a linear gradient of acetonitrile in water (both containing 0.5% formic acid). Detection was performed using a turboionspray source operated in positive ion mode and by multiple reaction monitoring (MRM; m/z 1111 --> 295 for APL and m/z 1113 --> 297 for didemnin B). The method was linear (r > or = 0.9933) over the range 1-250 ng/ml, with intra- and inter-batch precision and accuracy below 12.2% (except at LLOQ < or = 15.4%) for both plasma and urine. Recoveries were moderate, ranging from 54 to 70% in plasma and blood, and from 46 to 60% in urine, for both APL and didemnin B. The LOD was 0.25 ng/ml for both matrices. APL resulted stable in the different matrices at least for 6 h (both at room temperature and 37 degrees C), after freeze and thaw cycles and long term storage at -20 degrees C. The method allowed demonstrating that APL is in a dynamic equilibrium between plasma and blood cells. Moreover, the method was successfully applied to the pharmacokinetic study of Aplidin in cancer patients.     

Development of an ultra-performance liquid chromatography technique coupled with mass spectrometry for the measurement of tacrolimus in micro-samples of whole blood, and its application on a pharmacokiinetic trial

OBJECTIVE: The aim was to develop a rapid, specific, sensitive and accurate chromatographic technique coupled with mass spectrometry for the measurement of tacrolimus (CAS 104987-11-3) in microsamples of whole blood, and its application on a pharmacokinetic pilot trial. METHODS: A fast gradient was designed in an ultra-performance liquid chromatography, and coupled with a mass spectrometer for the quantification of tacrolimus in 100 microl samples of EDTA whole blood. Multiple reaction monitoring was used for the measurement of tacrolimus (m/z(+1) 821.49-->4768.35 Th) and sirolimus as internal standard (m/z(+1) 931.69-->864.39 Th). The method was validated according to Mexican regulatory guidelines. Twenty-four young healthy male volunteers with similar hematocrit values participated in the pharmacokinetic trial; an oral single dose of one 5 mg tacrolimus capsule was administered and kinetic profiles were described since 0 h until 24 h post-dose. RESULTS: Method showed to be accurate, precise and linear over the range from 1 to 80 ng/ml, having an absolute recovery of 94%. Molecule was stable for two months at -70 degrees C, and heparin interfered with its quantification. Total run-time is around 1.5 min. Mean maximum blood concentration was 32.63 +/- 1.74 ng/ml, and was reached at 1 h post-dose; elimination half-life was 14.18 +/- 5.71 h. CONCLUSIONS: Method developed is not time-consuming, inexpensive, and sensitive enough for its application during pharmacokinetic trials, and can be suitable for therapeutic drug monitoring in transplanted patients. Pharmacokinetic data obtained in Mexican population are quite similar to previously reported in international literature.     

Determination of oleanolic acid in human plasma and study of its pharmacokinetics in Chinese healthy male volunteers by HPLC tandem mass spectrometry

A highly selective and sensitive HPLC-ESI-MS-MS method was developed for the determination of oleanolic acid in human plasma. The oleanolic acid and glycyrrhetinic acid (internal standard) were recovered from plasma with ethyl acetate liquid-liquid extraction. The organic extracts were dried under a stream of warm nitrogen, reconstituted in mobile phase and injected into a Zorbax-Extend ODS analytical column (150 mm x 4.6 mm i.d., 5 microm), with the mobile phase consisting of methanol-ammonium acetate (32.5 mM) (85:15, v/v) pumped at a flow rate of 1.0 ml/min, and 30% of the eluent was split into a MS system with electrospray ionization tandem mass (ESI-MS-MS) detection in negative ion mode. The tandem mass detection was performed on a Finnigan Surveyor LC-TSQ Quantum Ultra AM tandem mass spectrometer operated in selected reaction monitoring mode. The parent to product ion combinations of m/z 455.4-->455.4 and 469.3-->425.2 at 38 V 1.5 mTorr Ar CID were used to quantify oleanolic acid and glycyrrhetinic acid, respectively. The assay was validated in the concentration range of 0.02-30.0 ng/ml for oleacolic acid when 0.5 ml of plasma was processed. The precision of the assay (expressed as relative standard deviation, R.S.D.%) was less than 15% at all concentrations levels within the tested range and adequate accuracy, and the limit of quantification was 0.02 ng/ml. The established method was applied for the pharmacokinetics study of oleanolic acid capsules in 18 healthy male Chinese volunteers with the mean values of C(max), T(max), AUC(0-48), AUC(0-infinity), t(1/2,) CL/F, and V/F of oleanolic acid after p.o. a single 40 mg dose obtained were 12.12 +/- 6.84 ng/ml, 5.2 +/- 2.9h, 114.34 +/- 74.87 ng h/ml, 124.29 +/- 106.77 ng h/ml, 8.73 +/- 6.11 h, 555.3 +/- 347.7 L/h, and 3371.1 +/- 1,990.1 L, respectively.     

Determination of lovastatin in human plasma by ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry and its application in a pharmacokinetic study

A selective, rapid and sensitive ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the quantitative determination of lovastatin in human plasma and its application in a pharmacokinetic study. With mycophenolate mofetil as internal standard, sample pretreatment involved a one-step extraction with tert-butyl methyl ether of 0.2 ml plasma. The analysis was carried out on an ACQUITY UPLCTM BEH C18 column (50 mm x 2.1 mm, i.d., 1.7 microm) with flow rate of 0.35 ml/min. The mobile phase was 20% water and 80% acetonitrile (v/v). The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI). Linear calibration curves were obtained in the concentration range of 0.08-24.50 ng/ml, with a lower limit of quantification of 0.08 ng/ml. The intra- and inter-day precision (RSD) values were below 15% and accuracy (RE) was -7.6 to 9.3% at all QC levels. The method was applicable to clinical pharmacokinetic study of lovastatin in healthy volunteers following oral administration.