In the current study, we established and validated a simple and sensitive liquid chromatography-tandem mass spectrometric method for the determination of 21-hydroxy deflazacort in nude mice plasma, and such a method was applied to a pharmacokinetic study. Using betamethasone as the internal standard, the plasma samples were pre-treated by precipitation with acetonitrile and then analyzed on a reversed-phase C18 column （50 mm×2 mm, 5 μm） with a mobile phase consisting of acetonitrile and 4.0 mM ammonium formate （pH was adjusted to 3.5 with formic acid （40：60, v/v））. The analyte was detected by a triple quadrupole tandem mass spectrometer using electrospray, and multiple reaction monitoring was employed to select 21-hydroxy deflazacort at m/z 400.2/124.0 and betamethasone at m/z 393.3/147.0 in the positive ion mode. The calibration curves were linear （r〉0.99） over the range of 0.5~,00 ng/mL. The intra- and inter-day precisions and accuracies were 4.5%-10.1% and -1.7%-10.7% respectively. This method was successfully applied to a preclinical administered with a single oral dose of 4 mg/kg deflazacort, and its pharmacokinetic study of deflazacort on female nude mice pharmacokinetics was characterized by a two-compartment model with first-order absorption.
In this investigation,sensitive and reproducible methods are described for quantitative determination of deflazacort in the presence of its degradation product.The method was based on high performance liquid chromatography of the drug from its degradation product on reverse phase using Acquity UPLC BEH C18columns（1.7 urn,2.1 mm ×150 mm） using acetonitrile and water（40：60 V/V） at a flow rate of 0.2 mL/minute in UPLC.UV detection was performed at 240.1 nm.Deflazacort was subjected to oxidative,acid,base,hydrolytic,thermal and photolytic degradation.The drug was found to be stable in water and thermal stress,as well as under neutral stress conditions.However,forced-degradation study performed on deflazacort showed that the drug degraded under alkaline,acid and photolytic stress.The degradation products were well resolved from the main peak,which proved the stability-indicating power of the method.The developed method was validated as per ICH guidelines with respect to accuracy,linearity,limit of detection,limit of quantification,accuracy,precision and robustness,selectivity and specificity.Apart from the aforementioned,the results of the present study also emphasize the importance of isolation characterization and identification of degradant.Hence,an attempt was made to identify the degradants in deflazacort.One of the degradation products of deflazacort was isolated and identified by the FTIR,NMR and LC-MS study.
