Budesonide quantification by HPLC coupled to atmospheric pressure photoionization (APPI) tandem mass spectrometry. Application to a comparative systemic bioavailability of two budesonide formulations in healthy volunteers.

In the present study, a novel, fast, sensitive and robust method to quantify budesonide in human plasma using 3-keto-desogestrel as the internal standard (IS) is described. The analyte and the IS were extracted from human plasma by liquid-liquid extraction (LLE) using ether. Extracted samples were analyzed by high performance liquid chromatography coupled to Atmospheric pressure photoionization tandem mass spectrometry (HPLC-APPI-MS/MS). Chromatography was performed isocratically on a C18, 5 µm analytical column. The temperature of the autosampler was kept at 6 °C and the run time was 4.00 min. A linear calibration curve over the range 7.5-1000 pg ml⁻¹ was obtained and the lowest concentration quantified was 7.5 pg ml⁻¹, demonstrating acceptable accuracy and precision. This analytical method was applied in a relative bioavailability study in order to compare a test budesonide 64 µg/dose nasal spray formulation vs. a reference 64 µg/dose nasal spray formulation (Budecort Aqua) in 48 volunteers of both sexes. The study was conducted in an open randomized two-period crossover design and with a one-week washout period. Plasma samples were obtained over a 14 h interval. Since the 90% CI for both C(max), AUC(last) and AUC(0-inf) were within the 80-125% interval proposed by the Food and Drug Administration and ANVISA, it was concluded that budesonide 64 µg/dose nasal spray was bioequivalent to Budecort Acqua® 64 µg/dose nasal spray, according to both the rate and extent of absorption.