Development and validation of a reverse-phase HPLC with fluorescence detector method for simultaneous determination of CZ48 and its active metabolite camptothecin in mouse plasma

A simple and sensitive high-performance liquid chromatography (HPLC) assay for the analysis of CZ48, a potent anticancer candidate, and its active metabolite camptothecin (CPT) in mouse plasma was developed and validated. CZ44 was used as an internal standard (IS). The samples were injected onto a C18 Synergi Polar-RP column (4 microm, 150 mm x 4.60 mm) maintained at 30 degrees C. The identification of peaks showed high specificity. Shimadzu RF-10AXL fluorescence detector was used at the excitation and emission of 380 and 418 nm, respectively. The mean recoveries were 81.41+/-0.035%, 86.00+/-0.053% and 82.21+/-0.020% for CZ48 and 76.01+/-0.028%, 77.04+/-0.042% and 85.93+/-0.023% for CPT at three concentrations of 10, 100 and 900 ng/ml, respectively. The calibration curve was linear (r(2)=0.9999) over CZ48 and CPT concentrations ranging from 5 to 1000 ng/ml and 10-1000 ng/ml (n=6), respectively. The method had an accuracy of >95% and intra- and inter-day precision (RE%) of <1.2% and <2.2% for CZ48 and CPT, respectively, at three different concentrations (10, 100 and 900 ng/ml). The lower limit of quantification (LLOQ) using 0.1 ml mouse plasma was 10 ng/ml for CZ48 and 5 ng/ml for CPT. Stability studies showed that CZ48 and CPT were stable in mouse plasma after 4h incubation at room temperature or after 1 month storage at -80 degrees C with three freeze/thaw cycles. The method reported is simple, reliable, precise and accurate and confirmed by the determination of plasma samples in the mice after oral administration of CZ48.     

Quantitation of itopride in human serum by high-performance liquid chromatography with fluorescence detection and its application to a bioequivalence study

A new method was developed for determination of itopride in human serum by reversed phase high-performance liquid chromatography (HPLC) with fluorescence detection (excitation at 291 nm and emission at 342 nm). The method employed one-step extraction of itopride from serum matrix with a mixture of tert-butyl methyl ether and dichloromethane (70:30, v/v) using etoricoxib as an internal standard. Chromatographic separation was obtained within 12.0 min using a reverse phase YMC-Pack AM ODS column (250 mm x 4.6 mm, 5 microm) and an isocratic mobile phase constituting of a mixture of 0.05% tri-fluoro acetic acid in water and acetonitrile (75:25, v/v) flowing at a flow rate of 1.0 ml/min. The method was linear in the range of 14.0 ng/ml to 1000.0 ng/ml. The lower limit of quantitation (LLOQ) was 14.0 ng/ml. Average recovery of itopride and the internal standard from the biological matrix was more than 66.04 and 64.57%, respectively. The inter-day accuracy of the drug containing serum samples was more than 97.81% with a precision of 2.31-3.68%. The intra-day accuracy was 96.91% or more with a precision of 5.17-9.50%. Serum samples containing itopride were stable for 180.0 days at -70+/-5 degrees C and for 24.0 h at ambient temperature (25+/-5 degrees C). The method was successfully applied to the bioequivalence study of itopride in healthy, male human subjects.     

Simultaneous determination of myristyl nicotinate, nicotinic acid, and nicotinamide in rabbit plasma by liquid chromatography-tandem mass spectrometry using methyl ethyl ketone as a deproteinization solvent

Myristyl nicotinate (Nia-114) is an ester prodrug being developed for delivery of nicotinic acid (NIC) into the skin for prevention of actinic keratosis and its progression to skin cancer. To facilitate dermal studies of Nia-114, a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using methyl ethyl ketone (MEK) as a deproteinization solvent was developed and validated for the simultaneous determination of Nia-114, NIC, and nicotinamide (NAM) in rabbit plasma. NAM is the principal metabolite of NIC, which is also expected to have chemopreventive properties. The analytes were chromatographically separated using a Spherisorb Cyano column under isocratic conditions, and detected by multiple reaction monitoring (MRM) in positive-ion electrospray ionization mode with a run time of 9 min. The method utilized a plasma sample volume of 0.2 ml and isotope-labeled D4 forms of each analyte as internal standards. The method was linear over the concentration range of 2-1000, 8-1000, and 75-1000 ng/ml, for Nia-114, NIC, and NAM, respectively. The intra- and inter-day assay accuracy and precision were within +/-15% for all analytes at low, medium, and high quality control standard levels. The relatively high value for the lower limit of quantitation (LLOQ) of NAM was demonstrated to be due to the high level of endogenous NAM in the rabbit plasma (about 350 ng/ml). Endogenous levels of NIC and NAM in human, dog, rat, and mouse plasma were also determined, and mean values ranged from <2 ng/ml NIC and 38.3 ng/ml NAM in human, to 233 ng/ml NIC and 622 ng/ml NAM in mouse. Nia-114 was generally unstable in rabbit plasma, as evidenced by loss of 44-50% at room temperature by 2 h, and loss of 64-70% upon storage at -20 degrees C for 1 week, whereas it was stable (<7% loss) upon storage at -80 degrees C for 1 month.     

Quantitative analysis of NIM811, a cyclophilin inhibitor, in human dried blood spots using liquid chromatography-tandem mass spectrometry

A high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method has been developed and validated for the quantitative analysis of NIM811, a cyclophilin inhibitor, in human dried blood spot (DBS) samples, which were produced by spotting 20 μl whole blood onto FTA cards. A 3mm disc was cut from the DBS samples and extracted using methanol, followed by liquid-liquid extraction with MTBE. The reconstituted extracts were chromatographed using a Halo C(18) column and gradient elution for MS/MS detection. The possible impact of hematocrit, blood sample volume and punching location on DBS sampling was investigated. The results showed that blood sample volume or punching location has no impact on assay performance, but the presence of a high hematocrit resulted in significantly increased analyte concentrations measured from the high QC samples. The current method was fully validated over the range of 10.0-5000 ng/ml with correlation coefficients (r(2)) for three validation batches equal to or better than 0.991. The accuracy and precision (CV) at the LLOQ were -0.7 to 6.0% bias of the nominal value (10.0 ng/ml) and 10.2-2.3%, respectively. For the balance of QC samples (20.0, 50.0, 750, 1500 and 3750 ng/ml), the precision (CV) ranged from 3.2 to 11.7% and from 5.6 to 10.2%, respectively, for the intra-day and inter-day evaluations. The accuracy ranged from -6.8 to 8.5% and -0.2% to 2.7% bias, respectively, for the intra-day and inter-day batches. NIM811 is stable in the DBS samples for at least 24h at room temperature and 4h at 60°C. Interestingly, the long term stability (LTS) assessment showed that the stability of the analyte is better when the DBS samples were stored at a lower storage temperature (e.g. ≤ -60°C) compared to storage at room temperature. This is probably due to the interaction of the additives and/or other materials (e.g. cellulose, etc) on the DBS card with NIM811, a cyclic peptide. The current methodology has been applied to determine the NIM811 levels in DBS samples prepared from a clinical study.     

Quantitative determination of cholesterol, sitosterol, and sitostanol in cultured Caco-2 cells by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

In this study, we describe a simple liquid extraction (methanol/choloroform, 1:1, v/v) method for endogenous free cholesterol and administered sterols extracted from cultured Caco-2 cells. To quantify sterol contents in Caco-2 cells, a new HPLC-APCI-MS method was developed. All the sterols were baseline separated using reversed-phase column (C8, 2.1 mm x 150 mm, 3.5 microm) and isocratic conditions (90%, v/v, methanol-water mixture containing 0.2 mM ammonium acetate). The full scan mass spectra of sterols were measured by an ion trap mass spectrometer equipped with an APCI ion source. The intense fragment ions resulting from the loss of water [M+H-H2O]+ (m/z 369, 395, 397 and 399 for cholesterol, stigmasterol, sitosterol, and sitostanol, respectively) were used for determinations. The absolute extraction recovery of sterols from the spiked cell samples were 109.7+/-26.2, 105.7+/-5.1, 109.8+/-5.0 and 99.0+/-7.0% for cholesterol, stigmasterol, sitosterol, and sitostanol, respectively. Furthermore, no significant matrix effect was observed for the sterols in the cell samples. The sample assay was based on the internal standard method using stigmasterol as an internal standard. The method was linear over the concentration ranges of 0.45-9.0 microM (cholesterol) and 0.225-7.2 microM (sitosterol and sitostanol). The within- and between-day precision was less than 7% and accuracy ranged from 93.51 to 101.77%. The lowest limit of quantitation (LLOQ) was 0.225 microM for sitosterol and sitostanol, and 0.45 microM for cholesterol. The accuracy range was 95-106% and precision was lower than 9% for all LLOQ values.     

Development of a highly sensitive high-performance liquid chromatographic method for measuring an anticancer drug, UCN-01, in human plasma or urine

We have established a highly sensitive high-performance liquid chromatographic method for the determination of an anticancer drug, UCN-01, in human plasma or urine. Using a fluorescence detector set at an excitation wavelength of 310 nm and emission monitored at 410 nm, there was a good linearity for UCN-01 in human plasma (r=0.999) or urine (r=0.999) at concentrations ranging from 0.2 to 100 ng/ml or 1 to 400 ng/ml, respectively. For intra-day assay, in plasma samples, the precision and accuracy were 1.8% to 5.6% and −10.0% to 5.2%, respectively. For inter-day assay, the precision and accuracy were 2.0% to 18.2% and 2.4% to 10.0%, respectively. In urine samples, the intra- and inter-day precision and accuracy were within 3.9% and ±2.7%, respectively. The lower limit of quantification (LLOQ) was set at 0.2 ng/ml in plasma and 1 ng/ml in urine. UCN-01 in plasma samples was stable up to two weeks at −80°C and also up to four weeks in urine samples. This method could be very useful for studying the human pharmacokinetics of UCN-01.     

Determination of glimepiride in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry

A sensitive and specific high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS-MS) method has been developed at our center for the determination of glimepiride in human plasma. After the addition of the internal standard, plasma samples were extracted by liquid-liquid extraction technique using diethyl ether. The compounds were separated on a prepacked C18 column using a mixture of acetonitrile, methanol and ammonium acetate buffer as mobile phase. A Finnigan LCQDUO ion trap mass spectrometer connected to an Alliance Waters HPLC was used to develop and validate the method. The analytical method was validated according to the FDA bioanalytical method validation guidance. The results were within the accepted criteria as stated in the aforementioned guidance. The method was proved to be sensitive and specific by testing six different plasma batches. Linearity was established for the range of concentrations 5.0-500.0 ng/ml with a coefficient of determination (r2) of 0.9998. Accuracy for glimepiride ranged from 100.58 to 104.48% at low, mid and high levels. The intra-day precision was better than 12.24%. The lower limit of quantitation (LLOQ) was identifiable and reproducible at 5.0 ng/ml with a precision of 7.96%. The proposed method enables the unambiguous identification and quantitation of glimepiride for pharmacokinetic, bioavailability or bioequivalence studies.     

Gas chromatography-mass spectrometry determination of matrine in human plasma

A method was developed for the quantification of matrine in human plasma using a liquid-liquid extraction procedure followed by gas-chromatography-mass spectrometry (GC/MS) analysis. Deuterated matrine, an internal standard of the analysis, was spiked into the plasma samples before extraction. Linear detection responses were obtained for matrine concentrations ranging from 10 to 500 ng/ml. The intra-day and inter-day precision ranged from 0.4 to 4.0% and 1.0-3.5%, respectively. The intra-day accuracy was between -7.3 and 4.5%. The limit of quantification for matrine was 23 ng/ml. The extraction efficiency averaged about 38%. The validated GC/MS method will be used to quantify matrine in human plasma samples collected in a clinical trial study.     

Validation of a sensitive and automated 96-well solid-phase extraction liquid chromatography-tandem mass spectrometry method for the determination of desloratadine and 3-hydroxydesloratadine in human plasma

To support clinical development, a liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed and validated for the determination of desloratadine (descarboethoxyloratadine) and 3-OH desloratadine (3-hydroxydescarboethoxyloratadine) concentrations in human plasma. The method consisted of automated 96-well solid-phase extraction for sample preparation and liquid chromatography/turbo ionspray tandem mass spectrometry for analysis. [2H(4)]Desloratadine and [2H(4)]3-OH desloratadine were used as internal standards (I.S.). A quadratic regression (weighted 1/concentration(2)) gave the best fit for calibration curves over the concentration range of 25-10000 pg/ml for both desloratadine and 3-OH desloratadine. There was no interference from endogenous components in the blank plasma tested. The accuracy (%bias) at the lower limit of quantitation (LLOQ) was -12.8 and +3.4% for desloratadine and 3-OH desloratadine, respectively. The precision (%CV) for samples at the LLOQ was 15.1 and 10.9% for desloratadine and 3-OH desloratadine, respectively. For quality control samples at 75, 1000 and 7500 pg/ml, the between run %CV was 相似文献   

Determination of ajulemic acid and its glucuronide in human plasma by gas chromatography-mass spectrometry

A method using gas chromatography-mass spectrometry (GC-MS) and solid-phase extraction (SPE) was developed for the determination of ajulemic acid (AJA), a non-psychoactive synthetic cannabinoid with interesting therapeutic potential, in human plasma. When using two calibration graphs, the assay linearity ranged from 10 to 750 ng/ml, and 750 to 3000 ng/ml AJA. The intra- and inter-day precision (R.S.D., %), assessed across the linear ranges of the assay, was between 1.5 and 7.0, and 3.6 and 7.9, respectively. The limit of quantitation (LOQ) was 10 ng/ml. The amount of AJA glucuronide was determined by calculating the difference in the AJA concentration before ("free AJA") and after enzymatic hydrolysis ("total AJA"). The present method was used within a clinical study on 21 patients suffering from neuropathic pain with hyperalgesia and allodynia. For example, plasma levels of 599.4+/-37.2 ng/ml (mean+/-R.S.D., n=9) AJA were obtained for samples taken 2 h after the administration of an oral dose of 20 mg AJA. The mean AJA glucuronide concentration at 2h was 63.8+/-127.9 ng/ml.     

Quantitative determination of the anticancer agent tubeimoside I in rat plasma by liquid chromatography coupled with mass spectrometry

Tubeimoside I is an important component isolated from Bolbostemma paniculatum. Tubeimoside I has been demonstrated to possess many pharmacological activities, including anti-inflammatory, antitumor, and antitumor-promoting effects. The purpose of the present study was to examine in vivo pharmacokinetics and bioavailability of tubeimoside I in rats by using a liquid chromatography coupled with mass spectrometry quantitative detection method (LC/MS). The plasma samples were deproteinated, evaporated and reconstituted in 100 microl methanol prior to analysis. The separation was performed by Waters Symmetry C18 reversed-phase column (3.5 microm, 150 mm x 2.1mm, Waters Inc., USA) and a SB-C18 guard column (5 microm, 20 mm x 4.0mm). The mobile phase was a mixture of acetonitrile and water containing 5 microM NaAc (60:40, v/v). The method was validated within the concentration range 20-5000 ng/ml, and the calibration curves were linear with correlation coefficients >0.999. The lowest limit of quantitation (LLOQ) for tubeimoside I was 20 ng/ml in 0.1 ml rat plasma. The intra-assay accuracy and precision ranged from 92.4 to 104.9% and from 5.8 to 10.5%, respectively, while inter-assay accuracy and precision ranged from 94.2 to 95.0% and from 5.1 to 8.8%, respectively. The method was further applied to assess pharmacokinetics and oral bioavailability of tubeimoside I after intravenous and oral administration to rats. The oral bioavailability of tubeimoside I is only 0.23%, which indicates that tubeimoside I has poor absorption or undergoes acid-induced degradation. Practical utility of this new LC/MS method was confirmed in pilot pharmacokinetic studies in rats following both intravenous and oral administration.     

Validation of a high-performance liquid chromatography method for tramadol and o-desmethyltramadol in human plasma using solid-phase extraction

An HPLC system using solid-phase extraction and HPLC with UV detection has been validated in order to determine tramadol and o-desmethyltramadol (M1) concentrations in human plasma. The method developed was selective and linear for concentrations ranging from 50 to 3500 ng/ml (tramadol) and 50 to 500 ng/ml (M1) with mean recoveries of 94.36±12.53% and 93.52±7.88%, respectively. Limit of quantitation (LOQ) was 50 ng/ml. For tramadol, the intra-day accuracy ranged from 95.48 to 114.64% and the inter-day accuracy, 97.21 to 103.24%. Good precision (0.51 and 18.32% for intra- and inter-day, respectively) was obtained at LOQ. The system has been applied to determine tramadol concentrations in human plasma samples for a pharmacokinetic study.     

Determination of rimantadine in rat plasma by liquid chromatography/electrospray mass spectrometry and its application in a pharmacokinetic study

A rapid and sensitive liquid chromatography/mass spectrometry (LC/MS) method was developed and validated for the determination of rimantadine in rat plasma. Rimantadine was extracted by protein precipitation with methanol, and the chromatographic separation was performed on a C(18) column. The total analytical run time was relatively short (4.6 min), and the limit of assay quantification (LLOQ) was 2 ng/mL using 50 microL of rat plasma. Rimantadine and the internal standard (amantadine) were monitored in selected ion monitoring (SIM) mode at m/z 180.2 and 152.1, respectively. The standard curve was linear over a concentration range from 2 to 750 ng/mL, and the correlation coefficients were greater than 0.999. The mean intra- and inter-day assay accuracy ranged from 100.1-105.0% to 100.3-104.0%, respectively, and the mean intra- and inter-day precision was between 1.3-2.3% and 1.8-3.0%, respectively. The developed assay method was successfully applied to a pharmacokinetic study in rats after oral administration of rimantadine hydrochloride at the dose of 20 mg/kg.     

Method development and validation of a high-performance liquid chromatographic method for tramadol in human plasma using liquid-liquid extraction

An HPLC system using a simple liquid-liquid extraction and HPLC with UV detection has been validated to determine tramadol concentration in human plasma. The method developed was selective and linear for concentrations ranging from 10 to 2000 ng/ml with average recovery of 98.63%. The limit of quantitation (LOQ) was 10 ng/ml and the percentage recovery of the internal standard phenacetin was 76.51%. The intra-day accuracy ranged from 87.55 to 105.99% and the inter-day accuracy, 93.44 to 98.43% for tramadol. Good precision (5.32 and 6.67% for intra- and inter-day, respectively) was obtained at LOQ. The method has been applied to determine tramadol concentrations in human plasma samples for a pharmacokinetic study.     

Sensitive quantification of ranolazine in human plasma by liquid chromatography--tandem mass spectrometry with positive electrospray ionization

A rapid, selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method with positive electrospray ionization (ESI) was developed for the quantification of ranolazine in human plasma. After liquid-liquid extraction of ranolazine and internal standard (ISTD) phenoprolamine from a 100 microl specimen of plasma, HPLC separation was achieved on a Nova-Pak C(18) column, using acetonitrile-water-formic acid-10% n-butylamine (70:30:0.5:0.08, v/v/v/v) as the mobile phase. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode using the transition m/z 428.5-->m/z 279.1 for ranolazine and m/z 344.3-->m/z 165.1 for the internal standard, respectively. Linear calibration curves were obtained in the concentration range of 5-4000 ng/ml, with a lower limit of quantitation (LLOQ) of 5 ng/ml. The intra- and inter-day precision values were below 3.7% and accuracy was within +/-3.2% at all three quality control (QC) levels. This method was found suitable for the analysis of plasma samples collected during the phase I pharmacokinetic studies of ranolazine performed in 28 healthy volunteers after single oral doses from 200 mg to 800 mg.     

On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples

Perphenazine enanthate has been used in wild animals as a tranquilizer during the period of adaptation to new environments to reduce stress, mortalities and injuries. A gas chromatographic procedure for the quantitative measurement of perphenazine in otter urine has been developed and validated. The method involved an enzymatic hydrolysis with beta-glucuronidase-arylsulfatase from Helix pomatia, followed by a solid-phase extraction with Bond Elut Certify cartridges. The resulting organic phase was evaporated, and the dry extract was derivatised with MSTFA to form the O-TMS derivative. The derivatised extracts were analysed by gas chromatography-mass spectrometry using SIM acquisition mode, measuring three diagnostic ions (m/z 246, 372 and 475). Another phenothiazine derivative, fluphenazine, was used as the internal standard (I.S.). Extraction recoveries for perphenazine and I.S. were 87.6 +/- 8.2% (n=4) and 106.7 +/- 13.4% (n=4), respectively. The calibration curves were linear in the range from 4 to 100 ng/ml (r2=0.99). The limits of detection and quantification were estimated as 1.2 and 3.5 ng/ml, respectively. Precision and accuracy obtained in intra-assay studies were in the ranges of 1.3-8.7 and 1.7-19.5%, respectively, using control samples containing 6, 16 and 60 ng/ml of perphenazine. In inter-assay experiments, precision ranged from 4.3 to 14.9% and accuracy from 3.1 to 11.8%. Examples of the application of the perphenazine quantification method in otter urines after administration of perphenazine enanthate are presented.     

Online solid phase extraction with liquid chromatography–tandem mass spectrometry to analyze remoxipride in small plasma-, brain homogenate-, and brain microdialysate samples

Remoxipride is a selective dopamine D₂ receptor antagonist, and useful as a model compound in mechanism-based pharmacological investigations. To that end, studies in small animals with serial sampling over time are needed. For these small volume samples currently no suitable analytical methods are available. We propose analytical methods for the detection of low concentrations remoxipride in small sample volumes of plasma, brain homogenate, and brain microdialysate, using online solid phase extraction with liquid chromatography–tandem mass spectrometry. Method development, optimization and validation are described in terms of calibration curves, extraction yield, lower limit of quantification (LLOQ), precision, accuracy, inter-day- and intra-day variability. The 20 μl plasma samples showed an extraction yield of 76%, with a LLOQ of 0.5 ng/ml. For 0.6 ml brain homogenate samples the extraction yield was 45%, with a LLOQ of 1.8 ng/ml. The 20 μl brain microdialysate samples, without pre-treatment, had a LLOQ of 0.25 ng/ml. The precision and accuracy were well within the acceptable 15% range. Considering the small sample volumes, the high sensitivity and good reproducibility, the analytical methods are suitable for analyzing small sample volumes with low remoxipride concentrations.     

A sensitive liquid chromatography-mass spectrometry method for simultaneous determination of two active chromones from Saposhnikovia root in rat plasma and urine

A sensitive and efficient liquid chromatography-mass spectrometry method was developed and validated for the simultaneous determination of two active chromones (prim-O-glucosylcimifugin and 4'-O-D-glucosyl-5-O-methylvisamminol) from Saposhnikovia root in rat plasma and urine. The plasma or urine samples were prepared by protein precipitation. Chromatographic separation of the two active chromones from matrix interferences was achieved on an Angilent TC-C(18) column with a mobile phase consisted of methanol, water and 0.1% formic acid. Puerarin was added as the internal standard. The method was validated with the concentration range 1.0-100 ng/mL in rat plasma and 10-1000 ng/mL in urine for prim-O-glucosylcimifugin, 1.5-150 ng/mL in plasma and 15-1500 ng/mL in urine for 4'-O-D-glucosyl-5-O-methylvisamminol. The lower limit of quantitation (LLOQ) of prim-O-glucosylcimifugin and 4'-O-D-glucosyl-5-O-methylvisamminol was 1.0 and 1.5 ng/mL in plasma, 10 and 15 ng/mL in urine, respectively. The intra- and inter-day precision across three validation days over the entire concentration range was lower than 9.0% as terms of relative standard deviation (R.S.D.). Accuracy determined at three quality control concentrations (2.0, 25 and 75 ng/mL for prim-O-glucosylcimifugin; 3.0, 37.5 and 112.5 ng/mL for 4'-O-D-glucosyl-5-O-methylvisamminol) ranged from -1.9 to 3.9% as terms of relative error (R.E.). The LC-ESI-MS method was further applied to assess pharmacokinetics and urine excretion of the two chromones after oral administration of Fangfeng extract to rats. Practical utility of this new LC-MS method was confirmed in pilot pharmacokinetic studies in rats following oral administration.     

Determination of tegaserod by LC-ESI-MS/MS and its application to a pharmacokinetic study in healthy Chinese volunteers

A simple, rapid and sensitive high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) assay for determination of tegaserod in human plasma using diazepam as internal standard (IS) was established. After adjustment to a basic pH with sodium hydroxide, plasma was extracted by ethyl acetate and separated by high performance liquid chromatography (HPLC) on a reversed-phase C18 column with a mobile phase of methanol: 5 mM ammonium acetate (75:25, v/v, adjusting the pH to 3.5 with glacial acetic acid). The quantification of target compounds was obtained by using multiple reaction monitoring (MRM) transitions; m/z 302.5, 173.2 and 285.4, 193.2 were measured in positive mode for tegaserod and internal standard (diazepam), respectively. The lower limit of quantification (LLOQ) was 0.05 ng/ml. The calibration curves were linear over the range 0.05-8.0 ng/ml (r=0.9996) for tegaserod. The mean absolute recovery of tegaserod was more than 85.56%. Intra- and inter-day variability values were less than 9.21% and 10.02%, respectively. The samples were stable for 8h under room temperature (25 degrees C, three freeze-thaw cycles in 30 days and for 30 days under -70 degrees C). After administration of a single dose of tegaserod maleate 4 mg, 6 mg and 12 mg, respectively, the area under the plasma concentration versus time curve from time 0 h to 12 h (AUC0-12) were (2.89+/-0.88), (5.32+/-1.21) and (9.38+/-3.42) ng h/ml, respectively; peak plasma concentration (Cmax) were (1.25+/-0.53), (2.21+/-0.52) and (4.34+/-1.66) ng/ml, respectively; apparent volume of distribution (Vd/F) were (6630.5+/-2057.8), (7615.2+/-2242.8) and (7163.7+/-2057.2) l, respectively; clearance rate (CL/F) were (1851.4+/-496.9), (1596.2+/-378.5) and (1894.2+/-459.3) l/h, respectively; time to Cmax (Tmax) were (1.00+/-0.21), (1.05+/-0.28) and (1.04+/-0.16) h, respectively; and elimination half-life (t1/2) were (3.11+/-0.78), (3.93+/-0.92) and (3.47+/-0.53) h, respectively; MRT were (3.74+/-0.85), (4.04+/-0.56) and (3.28+/-0.66) h, respectively. The essential pharmacokinetic parameters after oral multiple doses (6mg, b.i.d) were as follows: Cssmax, (2.72+/-0.61) ng/ml; Tmax, (1.10+/-0.25) h; Cssmin, (0.085+/-0.01) ng/ml; Cav, (0.54+/-0.12) ng/ml; DF, (4.84+/-0.86); AUCss, (6.53+/-1.5) ngh/ml. This developed and validated assay method had been successfully applied to a pharmacokinetic study after oral administration of tegaserod maleate in healthy Chinese volunteers at a single dose of 4 mg, 6 mg and 12 mg, respectively. The pharmacokinetic parameters can provide some information for clinical medication.     

Quantitative determination of glycopyrrolate in human plasma by liquid chromatography-electrospray ionization mass spectrometry: the use of a volatile ion-pairing agent during both liquid-liquid extraction and liquid chromatography

The work presented here deals with the development of a quantitative tool for the determination of the quaternary ammonium anticholinergic glycopyrrolate in human plasma samples. Mepenzolate was used as an internal standard. The plasma samples were subjected to a suitable sample clean-up consisting of a simple and relatively fast, two step liquid-liquid ion-pair extraction procedure. The chromatography, using the same volatile ion-pair reagent heptafluorobutyric acid (HFBA), takes only 10 min. Relative standard deviation of retention times was never above 2.26% (n=36). The method was fully validated based on the US FDA Bioanalytical Method Validation Guidance for Industry. As such, a quantitative ESI-LC-MS(/MS) (TOF mass spectrometry) method was optimized for the absolute quantification of glycopyrrolate in human plasma in a concentration range from 0.101 to 101 ng/mL using a quadratic calibration function (R(2)=0.9995), y=-2.21 x 10(-4) (+/-3.93 x 10(-5))xx(2)+5.85 x 10(-2) (+/-5.27 x 10(-3))xx+4.08 x 10(-3) (+/-4.82 x 10(-4)). For the three QC concentrations (QC(1) 0.252, QC(2) 2.52, and QC(3) 25.2ng/mL) and the LLOQ (0.101 ng/mL), total precision was under 20% (18.0% (n=6) at the LLOQ) and maximum accuracy was 112% (88.9% for the LLOQ, n=6). Absolute matrix effect (maximum 133%+/-9.59, n=3), absolute recovery (better than 41.8%+/-2.22, n=3), relative (inter-subject) matrix effect (maximum 10.9%+/-1.45, n=4) and process efficiency (better than 45.2%+/-5.74, n=3) too were assessed at the 3 QC concentrations.