Detection of budesonide in human urine after inhalation by liquid chromatography–mass spectrometry

Budesonide, a corticosteroid frequently used in the treatment of asthma, is most often administered via inhalation. Its use in sports is allowed when medically necessary. A fast, sensitive and accurate LC–MS method was developed and validated for the quantification of budesonide and its major metabolite 16α-hydroxyprednisolone in urine samples after inhalation of a metered dose (Pulmicort-Turbohaler®200).Sample preparation consists of an alkaline liquid–liquid extraction with ethyl acetate. Analysis was performed using liquid chromatography–tandem mass spectrometry with electrospray ionization (ESI). The method was linear in the range of 5–100 and 0.5–10 ng/mL for 16α-hydroxyprednisolone and budesonide, respectively. The limits of quantification were 5 ng/ml for 16α-hydroxyprednisolone and 0.5 ng/mL for budesonide. The accuracy ranged from 2.2 to 3.5% for 16α-hydroxyprednisolone and from 0.8 to 16.4% for budesonide. After administration of 200 μg of budesonide to five healthy volunteers budesonide could not be detected in any urine sample whereas 16α-hydroxyprednisolone was detectable up to 12 h post-administration.