An LC-MS/MS method for the determination of budesonide and 16α-hydroxyprednisolone in dog plasma

Although budesonide is frequently used in veterinary medicine for the treatment of canine respiratory and bowel inflammatory diseases, knowledge is lacking regarding its kinetics in this species. We developed and validated a liquid chromatography–tandem mass spectrometry method for the determination of budesonide and its metabolite 16a-hydroxyprednisolone in dog plasma. The analytes were extracted by solid phase extraction and analysis was performed by high performance liquid chromatography–tandem mass spectrometry, with positive electrospray ionization. This method allows budesonide and one of its main metabolites to be simultaneously quantified in dog plasma at fairly low concentrations. The proposed protocol is very easy and fast to execute, without compromising analytical performances. A small amount (0.5mL) of plasma is required, making this approach suitable for pharmacokinetic studies also in small sized dogs.