ABSTRACT
A sensitive and efficient liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantitative determination of diflucortolone in rabbit plasma after dermal administration of diflucortolone valerate cream to rabbits. After extraction with ethyl acetate, the chromatographic separation was performed on Zorbax Eclipse XDB-C18 (50 mm×4.6 mm, 5 μm) with a gradient mobile phase consisting of 50% acetonitrile-50% methanol and 0.1% formic acid-5% methanol-5 mmol·L-1 ammonium formate at a flow rate of 0.35 mL·min-1. The quantitative analysis was carried out using multiple reaction monitoring (MRM) at specific ion transitions of m/z [M+H]+ 395.2→m/z 355.2 for diflucortolone and m/z [M+H]+ 258.1→m/z 120.9 for ethoxyphenylethylamine (internal standard) in positive ion mode with electrospray ionization (ESI) source. This validated LC-MS/MS method had a linearity over the concentration range of 0.01-10 ng·mL-1 with the lower limit of quantification (LLOQ) at 0.01 ng·mL-1. At level of LLOQ, the inter and intra-assay precision (RSD) were no greater than 9.82% and 11.0%, respectively. The main pharmacokinetic parameters of the diflucortolone including tmax, Cmax, AUC0-72 h, and t1/2 were as follows: (6.33±1.21) h, (0.168±0.080 0) ng·mL-1, (3.15±0.834) h·ng·mL-1, (32.0±17.4) h. The method was validated in the pharmacokinetic study of diflucortolone in rabbit following dermal administration of diflucortolone valerate cream at dose of 0.01 g·cm-2. In this study, the program of animal testing had been approved by Committee on the management and usage of experimental animal in the Evaluation Company of Innovative Drug, Tianjin Institute of Pharmaceutical Research.
ABSTRACT
OBJECTIVE: To determine gatifloxacin in human plasma, and study the exposure characteristics of gatifloxacin in Chinese healthy male volunteers who used Gatifloxacin Eye Gel for 7 d. METHODS: LC-MS/MS method was developed for the quantitation of gatifloxacin in human plasma After protein precipitation with methanol and dilution with water, the chromatographic separation was carried out on an Symmetry C18 column (4.6 mm × 100 mm, 5 μm) with a gradient mobile phase consisting of 0.1% formic acid in methanol and 0.1% formic acid in water at a flow rate of 0.5 mL · min-1. The quantitation analysis was performed using multiple reaction monitoring (MRM) at the specific ion transitions of m/z 376.2→261.0 for gatifloxacin and m/z 332.1→-288.1 for ciprofloxacin (internal standard) in the positive ion mode with electrospray ionization (ESI) source. Specificity, linearity, precision and accuracy, matrix effects, recovery and stability were investigated to validate the LC-MS/MS method. Plasma samples of different times from 10 Chinese healthy male volunteers were determined, who used Gatifloxacin Eye Gel for 7 d. RESULTS: The linear range was 2 -500 ng · mL-1. The intra- and inter-day precisions were less than 2.61% and 13.1%, and the accuracy was within ±5.0%. Matrix effective, recovery, specificity and stability were within ± 15.0%. The concentration of gatifloxacin in human plasma was below the lower limit of quantitation (2 ng · mL-1). CONCLUSION: This method is sensitive and accuracy for the determination of gatifloxa-cinin human plasma, and the plasma gatifloxacin level are all below the lower limit of quantitation (2 ng · mL-1) in all subjects.