title: Elimination kinetics of dexamethasone in bovine urine, hair and feces following single administration of dexamethasone acetate and phosphate esters.
abstract: Corticosteroids are hormonal substances widely used in human and veterinary medicine for their anti-inflammatory properties. Among the numerous existing artificial corticosteroids, dexamethasone remains the most commonly used, mainly throughout esterified forms such as acetate or phosphate. An experimental study was designed to assess its drug residue levels in urine and feces, as well as its fixation in bovine hair following a single administration of 0.15 mg/kg b.w. dexamethasone acetate and 0.12 mg/kg b.w. dexamethasone sodium phosphate. Different analytical methods based on GC-MS or LC-MS/MS were used for measuring dexamethasone and its esterified forms, which were implemented in 3 different European laboratories in the field that collaborated for this study. The obtained results confirmed the high and rapid urinary excretion rate of dexamethasone, with a maximal concentration (267 μg/L) measured one day after administration and 98% elimination within 3 days. The concentrations obtained with the GC-NCI-MS procedure (using chemical oxidation as derivatization) were found significantly higher than the ones obtained with LC-ESI-MS/MS, indicating a possible contribution of dexamethasone phase I and/or II metabolites to the monitored signal. Fecal elimination was also found rapid (95% elimination within 3 days) with a maximum concentration level (28.5 μg/kg) observed one day after administration. Detectable levels of dexamethasone in hair appeared on day 2 (11.5 μg/kg), reached a maximum around one week, and could be identified until 22 days upon treatment, establishing the suitability of hair as a biological matrix for medium to long-term residue controls of dexamethasone.
authors.affiliation: Ghent University, Faculty of Veterinary Medicine, Research Group of Veterinary Public Health and Zoonoses, Laboratory of Chemical Analysis, Salisburylaan 133, B-9820 Merelbeke, Belgium. Lynn.Vanhaecke@ugent.be
authors.forename: Lynn
authors.initials: L
authors.lastname: Vanhaecke
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Antignac
authors.forename: Dirk
authors.initials: D
authors.lastname: Courtheyn
authors.forename: Bruno
authors.initials: B
authors.lastname: Le Bizec
authors.forename: Hubert
authors.initials: H
authors.lastname: De Brabander
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002417:Cattle; D003907:Dexamethasone / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000652:urine; D005243:Feces / Q000737:chemistry*; D006197:Hair / Q000737:chemistry*; D007700:Kinetics; D008968:Molecular Conformation; D011786:Quality Control; D013237:Stereoisomerism
chemical_list: D003907:Dexamethasone