ABSTRACT
The study aims to establish an LC-MS/MS method for the determination of S-(+)-ibuprofen (S-IBP) and R-(-)-ibuprofen (R-IBP), which may be used subsequently to investigate the pharmacokinetics of ibuprofen enantiomers in healthy Chinese volunteers. Naproxen was used as an internal standard. The separation was achieved on a Chiralpak AD-3R column (4.6 mm×150 mm, 3.0 μm) with a mobile phase consisting of acetonitrile/0.01% formic acid aqueous solution (40:60) at a flow rate of 750 μL·min-1 within 23.0 min. Naproxen and the internal standard were measured by a triple-quadrupole mass spectrometer in negative electron electronic spray ion (ESI) mode using multiple reaction monitoring (MRM). The extracted ions monitored following MRM transitions were m/z 205.1→161.0 for ibuprofen enantiomers and m/z 229.1→185.0 for the internal standard naproxen. Plasma samples were pretreated through methanol precipitation. The calibration curve of S-IBP and R-IBP in human plasma was linear over the concentration rang of (0.05-30.00) μg·mL-1. The lower limit of quantitation was 0.05 μg·mL-1. The intra-and inter-run precisions of S-IBP at three quality control levels were within 2.2%-4.2%, the relative deviation of the assay was within -12.0%-13.0%. The intra-and inter-run precisions of R-IBP at three quality control levels were within 2.0%-8.2%, the relative deviation of the assay was within -11.5%-10.6%. The plasma samples were stable at room temperature (25℃) for 6 h, at -30℃ for 47 days and during three freeze-thaw cycles. The method was proved to be convenient, accurate and sensitive, and suitable for the pharmacokinetics study of ibuprofen enantiomers in healthy Chinese volunteers after a single oral dose of 300 mg ibuprofen extended-release capsule.
ABSTRACT
The study was aimed to establish a liquid chromatography-tandem mass spectrometric method for the determination of the duloxetine concentration in rat plasma, and compare the pharmacokinetics in normal and diabetes mellitus rat models. Diazepam was used as an internal standard. The separation was achieved on a Waters Xterra® RP18 column (100 mm × 4.6 mm, 3.5 μm) with a mobile phase consisting of methanol -0.3% formic acid containing 5 mmol·L-1 ammonium acetate (75:25) at the flow rate of 0.6 mL·min-1. Electrospray ionization source was applied and operated in the positive multiple reaction monitoring mode. A good linearity of duloxetine was obtained in the concentration range of 10-5 000 ng·mL-1. The rat models of diabetes mellitus were established by intraperitoneal injection of streptozotocin. The same dose of duloxetine (40 mg·kg-1) was given by intragastric administration to the normal and diabetic rats. Blood samples were collected from the orbital venous plexus to determinate duloxetine concentration in the plasma. The pharmacokinetic parameters were calculated by DAS software. Statistical analysis was performed by SPSS software. The major pharma-cokinetic parameters of diabetes group were as follows: Cmax was 1 185 ± 190.0 ng·mL-1; AUC0-∞ was 8 398 ± 1 835 ng·mL-1·h; tmax was 1.6 ± 0.4 h; t1/2z was 3.6 ± 0.9 h. The major pharmacokinetic parameters of normal group were as follows: Cmax was 368.1 ± 40.7 ng·mL-1; AUC0-∞ was 4145 ± 640.1 ng·mL-1·h; tmax was 1.6 ± 0.3 h; t1/2z was 4.1 ± 0.8 h. The results of pharmacokinetic experiments suggest that the exposure amount of duloxetine in diabetic rats is twice higher than that in normal rats.