Pharmacokinetic and urinary profiling reveals the prednisolone/cortisol ratio as a valid biomarker for prednisolone administration

Abstract

BackgroundIn Europe, synthetic corticosteroids are not allowed in animal breeding for growth-promoting purposes. Nevertheless, a high prevalence of non-compliant urine samples was recently reported for prednisolone, however, without any indication of unauthorized use. Within this context, 20β-dihydroprednisolone and the prednisolone/cortisol ratio have been suggested as potential tools to discriminate between exogenous and endogenous urinary prednisolone. In this study, the validity of these strategies was verified by investigating the plasma pharmacokinetic and urinary excretion profiles of relevant glucocorticoids in bovines, subjected to exogenous prednisolone treatment or tetracosactide hexaacetate administration to induce endogenous prednisolone formation. Bovine urine and plasma samples were analysed by liquid chromatography and mass spectrometry.ResultsBased on the plasma pharmacokinetics and urinary profiles, 20β-dihydroprednisolone was confirmed as the main prednisolone-derived metabolite, being detected in the biological fluids of all 12 bovines (plasma AUC0-inf of 121 h μg L−1 and urinary concentration > 0.695 μg L−1). However, this metabolite enclosed no potential as discriminative marker as no significant concentration differences were observed upon exogenous prednisolone treatment or tetracosactide hexaacetate administration under all experimental conditions. As a second marker tool, the prednisolone/cortisol ratios were assessed along the various treatments, taking into account that endogenous prednisolone formation involves the hypothalamic-pituitary-adrenal axis and is associated with an increased cortisol secretion. Significantly lower ratios were observed in case of endogenous prednisolone formation (i.e. ratios ranging from 0.00379 to 0.129) compared to the exogenous prednisolone treatment (i.e. ratios ranging from 0.0603 to 36.9). On the basis of these findings, a discriminative threshold of 0.260 was proposed, which allowed classification of urine samples according to prednisolone origin with a sensitivity of 94.2% and specificity of 99.0%.ConclusionThe prednisolone/cortisol ratio was affirmed as an expedient strategy to discriminate between endogenous and exogenous prednisolone in urine. Although the suggested threshold value was associated with high specificity and sensitivity, a large-scale study with varying experimental conditions is designated to optimize this value.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-017-1158-5) contains supplementary material, which is available to authorized users.

Effects of truck transportation and slaughtering on the occurrence of prednisolone and its metabolites in cow urine, liver, and adrenal glands

“…Although the urine of the cows undergoing such a pharmacological treatment exhibited the occurrence of natural corticoids levels similar to those found in slaughtered cows, no plausible explanation was provided to justify the apparent discrepancy between absence and presence of prednisolone in naturally and artificially stressed animals, respectively. More recently, van Meulebroek et al [10] reported the detection of 20β-dihydroprednisolone in all urine specimens collected from cows subjected to prednisolone treatment, under either therapeutic or (oral) growth-promoting schedule, as well as in cows treated (by i.m. injection) with tetracosactide to induce a pharmacological stress.…”

“…Based on the evidences presently available, the reasons for the seemingly different urinary pattern profile of prednisolone metabolites between naturally and artificially stressed cows remain to be elucidated. As a matter of fact, besides the cases of pharmacologically-induced stress, the presence of 20β-dihydroprednisolone and other prednisolone metabolites in the cattle urine has been so far consistently associated only with the exogenous administration of the parent drug, either following a growth-promoting protocol or a therapeutic schedule [8, 10, 13].…”

“…Endogenous prednisolone was found in the urines and adrenal glands [9] of dairy cows subjected to the distinctive state of stress consequent to their transport and slaughter. More recently [10], the plasma pharmacokinetic and urinary excretion profiles of relevant glucocorticoids were investigated in cattle subjected to either exogenous prednisolone treatment or the administration of synthetic ACTH analogue tetracosactide hexaacetate to induce a stress allegedly leading to endogenous prednisolone formation. The results of this study point to the determination of the urinary prednisolone/cortisol ratio as an expedient strategy to discriminate between endogenous and exogenous prednisolone.…”