Normal-phase liquid chromatography coupled with electrospray ionization mass spectrometry for chiral separation and quantification of clevudine and its enantiomer in human plasma.

A new, simple and enantioselective normal-phase liquid chromatography-mass spectrometry method was presented for the quantification of clevudine and its enantiomer in human plasma. A C18 cartridge was used in this method to extract the enantiomers in 200µL plasma followed by a chiral separation on a cellulose-based LC column with mobile phase consisted of hexane, methanol and ethanol (62:28:10, V/V/V). The eluate was directed to a mass spectrometry through an electrospray ionization interface. A transition of m/z 261.0 to m/z 126.8 was used for monitoring of clevudine and its enantiomer. This method showed good linearity (R>0.997), precision (<9.6%) and accuracy (within 95.48-105.9%) within a range of 10-1000ng/mL for the enantiomers and has been applied to the pharmacokinetics study of clevudine capsules in human plasma.

Simultaneous determination of ipratropium and salbutamol in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A novel, sensitive and specific LC-MS/MS method with silica-based solid-phase extraction was developed for simultaneous determination of ipratropium (IPR) and salbutamol (SAL) in rat plasma. Chromatographic separation was achieved on a Shiseido Capcell Pak CR column (SCX:C(18)=1:4, 150 mm × 2.0 mm, 5 µm) with a mobile phase consisting of methanol/water (85:15, v/v) containing 20 mmol/L ammonium formate and 0.1% formic acid at a flow rate of 0.3 mL/min. A tandem mass spectrometric detection with an electrospray ionization (ESI) interface was conducted via multiple reaction monitoring (MRM) under positive ionization mode. This method was validated in terms of specificity, linearity, accuracy (within ±115.4%), intra- and inter-day precision (<11.4%) over the concentration range of 8-1612 pg/mL for IPR and 50-10,000 pg/mL for SAL. In addition, stability and matrix effects of IPR and SAL in plasma were evaluated. This method has been successfully applied to the pharmacokinetic study of compound ipratropium bromide aerosol mainly containing ipratropium bromide (IB) and salbutamol sulphate (SS) after inhalation in rats.

Simultaneous determination of lamivudine, stavudine and nevirapine in human plasma by LC-MS/MS and its application to pharmacokinetic study in clinic.

A new high-throughput LC-MS/MS method for the simultaneous determination of lamivudine (3TC), stavudine (d4T) and nevirapine (NVP) in human plasma is presented, with zidovudine as an internal standard. The analytes were extracted from plasma by protein precipitation and only 150 microL plasma was needed. Chromatographic separation was achieved on a Shiseido C(8) column (150 x 2.0 mm, 5 microm) with a total run time of 6 min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring under positive ionization mode with an electrospray ionization interface. The method was developed and validated over the concentration range of 25-5000 ng/mL for 3TC and NVP and 20-4000 ng/mL for d4T. The method was validated in terms of intra- and inter-day precision (< or = 8.6%), accuracy (within +/- 8.4%), linearity and specificity. The method has been successfully applied to the pharmacokinetic study of a combination treatment of 300 mg lamivudine, 30 mg stavudine and 200 mg nevirapine in 22 healthy male volunteers under fasting conditions.

[Simultaneous determination of gestodene, etonogestrel and ethinylestradiol in plasma by LC-MS/MS following derivatization].

To establish a sensitive and specific method for simultaneous determination of gestodene, etonogestrel and ethinylestradiol in plasma by LC-MS/MS, plasma samples were extracted and derivatized before injection. An ESI ion source was used and operated in the positive ion mode with multiple reaction monitoring (MRM). Norgestrel was chosen as internal standard and performed on a C18 (100 mm x 2.1 mm, 5 microm) column. The concentrations of gestodene, etonogestrel and ethinylestradiol were measured, using step-gradient mobile phase and step-gradient flow rate. The method was validated over the concentration range of 0.1-20 ng x mL(-1) for gestodene and etonogestrel and 0.01-2 ng x mL(-1) for ethinylestradiol, and showed excellent linearity. The intra- and inter-assay accuracy and precision were below 10.0% and recovery was 93.6%-110.9% over the three concentration levels evaluated. The method was applied in pharmacokinetic study of the compound gestodene patch and the compound etonogestrel patch in rabbits. The LC-MS/MS method was selective, accurate and sensitive, especially the LOQ were 100 pg x mL(-1) for gestodene and etonogestrel and 10 pg x mL(-1) for ethinylestradiol. The method was successfully applied in pharmacokinetic study for contraceptives.

Determination of norelgestromin in rabbit plasma by LC-MS/MS and its application to the pharmacokinetic study of ORTHO EVRA.

A simple, sensitive and rapid method is presented for the determination of norelgestromin using LC-MS/MS, interfaced via an electrospray ionization (ESI) probe, operating in the positive ion mode with multiple reaction monitoring (MRM). The method was developed and validated over the concentration range of 0.05-20 ng/ml, and showed excellent linearity. The intra- and inter-assay accuracy error and precision were ranging from -2.3% to 6.0% of nominal values and 2.2% to 7.8% over the three concentration levels evaluated. The concentration of formic acid in mobile phase was optimized to achieve satisfactory injection reproducibility and sensitivity, and sample preparation was optimized, with only 1.6 ml organic solvents used in performing the liquid-liquid extraction. The method has been successfully applied to a pharmacokinetic study of the ORTHO EVRA patch in rabbits.

Simultaneous determination of ginkgolides A, B, C and bilobalide in plasma by LC-MS/MS and its application to the pharmacokinetic study of Ginkgo biloba extract in rats.

A new liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous determination of ginkgolides (includes ginkgolide C for the first time) and bilobalide in plasma is presented. Ketoprofen was used as an internal standard, and sample pre-treatment consisted of a liquid-liquid extraction. Chromatographic separation was achieved on a 5 microm Shiseido C8 column (150 mm x 2.0 mm i.d., particle size 5 microm) with a mobile phase consisting of methanol/ 6 mM ammonium acetate (60/40, v/v) at a flow rate of 0.3 ml/min. A tandem mass spectrometric detection was conducted using multiple reaction monitoring (MRM) under negative ionization mode with an atmospheric pressure chemical ionization (APCI) interface. The method was validated in terms of intra- and inter-day precision (<12.7%), accuracy (within +/- 7.0%), linearity, specificity and stability. In addition, matrix effects of ginkgolides and bilobalide in plasma were evaluated in different reconstitution solvents. Smaller matrix effects were observed for reconstitution solvents containing less organic solvent. The method has been successfully applied to a pharmacokinetic study of Ginkgo biloba extract in rats after intravenous administration. This is the first report of pharmacokinetic data for ginkgolide C.

Simultaneous determination of metformin and glipizide in human plasma by liquid chromatography-tandem mass spectrometry.

A method has been developed for the simultaneous quantification of metformin (I) and glipizide (II) in human plasma. It is based on high-performance liquid chromatography with electrospray ionization tandem mass (LC-ESI-MS/MS) spectrometric detection in positive ionization mode. Phenformin (III) and gliclazide (IV) were used as internal standards for I and II, respectively. The MS/MS detection was performed in multiple reaction monitoring (MRM) mode. The precursor-product ion combinations of m/z 130 --> 71, 446 --> 321, 206 --> 60 and 324 --> 127 were used to quantify I, II, III and IV, respectively. This method was validated in the concentration ranges of 0.02-4 microg/mL for I and 0.004-0.8 microg/mL for II. It was utilized to support a clinical pharmacokinetic study after single dose oral administration of a combination of I and II.

[Simultaneous determination of pseudoephedrine and chlorpheniramine in human plasma by HPLC-UV detection method].

AIM: To establish a sensitive and specific method to simultaneous determination of pseudoephedrine and chlorpheniramine in human plasma. METHODS: Pseudoephedrine and chlorpheniramine were extracted from alkaline plasma with t-butyl methyl ether as the base form, and were back-extracted into 1.5% hydrochloride solution. The two drugs were simultaneous determined by RP-HPLC with ultraviolet detection at 200 nm, using dextromethorphan as internal standard. A C18 column (250 mm x 46 mm ID) and a mobile phase containing acetonitrile-water-triethylamine (46:54:0.2, containing 10 mmol x L(-1) sodium dodecyl sulfate (SDS) and 60 mmol x L(-1) NaH2 PO4, adjusted pH to 2.6 with H3PO4) were used. RESULTS: The limit of quantification was 10.0 and 0.5 microg x L(-1), the linear range was 1.5 - 0.01 mg x L(-1) and 75 - 0.5 microg x L(-1), for pseudoephedrine and chlorpheniramine, respectively. The within-day and between-day RSD were less than 12.4%, and the average recovery was between 97.3% - 109.4%. CONCLUSION: The method was sensitive, specific, simple, and suitable for drug level monitoring in clinical pharmacokinetic study.