Determination of 21-hydroxydeflazacort in human plasma by high-performanceliquid chromatography/atmospheric pressure chemical ionization tandem massspectrometry. Application to bioequivalence study

A liquid chromatographic atmospheric pressure chemical ionization tandem ma ss spectrometric method is described for the determination of 21-hydroxydef lazacort in human plasma using dexamethasone 21-acetate as an internal stan dard. The procedure requires a single diethyl ether extraction, After evapo ration of the solvent under a nitrogen flow, the analytes are reconstituted in the mobile phase, chromatographed on a Cls reversed-phase column and an alyzed by mass spectrometry via a heated nebulizer Interface where they are detected by multiple reaction monitoring. The method has a chromatographic run time of less than 5 min and a Linear calibration curve with a range of 1-400 ng ml(-1) (r > 0.999), The between-run precision based on the relati ve standard deviation for replicate quality controls, was less than or equa l to 5.5% (10 ng ml(-1)), 1.0% (50 ng ml(-1)) and 2.7% (200 ng ml(-1)). The between-run accuracy,vas +/-7.1, 3.8 and 4.8% for the above concentrations , respectively. This method was employed in a bioequivalence study of two D FZ tablet formulations (Denacen from Marjan Industria e Comercio, Brazil, a s a test formulation, and Calcort from Merrell Lepetit, Brazil, as a refere nce formulation) in 24 healthy volunteers of both sexes who received a sing le 30 mg dose of each formulation. The study aas conducted using an open, r andomized, two-period crossover design with a 7-day washout interval. The 9 0% confidence interval (CT) of the individual geometric mean ratio for Dena cen/Calcort was 89.8-109.5% for area under the curve AUC((0-24 h)) and 80.7 -98.5% for C-max. Since both the 90% CI For AUC((0-24) (h)) and C-max were included in the 80-125% interval proposed by the US Food and Drug Administr ation, Denacen was considered bioequivalent to Calcort according to both th e rate and extent of absorption. Copyright (C) 2000 John Wiley & Sons, Ltd.