Abstract

The cortisol response to glucocorticoid intervention has, in spite of several studies in horses, not been fully characterized with regard to the determinants of onset, intensity and duration of response. Therefore, dexamethasone and cortisol response data were collected in a study applying a constant rate infusion regimen of dexamethasone (0.17, 1.7 and 17g/kg) to six Standardbreds. Plasma was analysed for dexamethasone and cortisol concentrations using UHPLC-MS/MS. Dexamethasone displayed linear kinetics within the concentration range studied. A turnover model of oscillatory behaviour accurately mimicked cortisol data. The mean baseline concentration range was 34-57g/L, the fractional turnover rate 0.47-1.5 1/h, the amplitude parameter 6.8-24g/L, the maximum inhibitory capacity 0.77-0.97, the drug potency 6-65ng/L and the sigmoidicity factor 0.7-30. This analysis provided a better understanding of the time course of the cortisol response in horses. This includes baseline variability within and between horses and determinants of the equilibrium concentration-response relationship. The analysis also challenged a protocol for a dexamethasone suppression test design and indicated future improvement to increase the predictability of the test.

Published in

Journal of Veterinary Pharmacology and Therapeutics
2016, Volume: 39, number: 3, pages: 255-263

SLU Authors

• Ekstrand, Carl

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Ingvast Larsson, Carina

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Olsén, Lena

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

• Gabrielsson, Johan

  • Department of Animal Biosciences, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Pharmacology and Toxicology


Publication identifier

DOI: https://doi.org/10.1111/jvp.12276

Permanent link to this page (URI)

https://res.slu.se/id/publ/69365