Abstract:

In the current study, we established and validated a simple and sensitive liquid chromatography-tandem mass spectrometricmethod 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 0.5–400 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 pharmacokinetic study of deflazacort on female nude mice administered with a single oral dose of 4 mg/kg deflazacort, and its pharmacokinetics was characterized by a two-compartment model with first-order absorption. 

Key words: Deflazacort, 21-Hydorxy deflazacort, LC-MS/MS, Nude mice, Pharmacokinetics