Effects of dermal dexamethasone application on ACTH and both basal and ACTH-stimulated cortisol concentration in normal horses.
Abstract: There are no data available regarding the systemic (adverse) effects which might be induced by topical/dermal glucocorticoids (GCs) application in the horse. Besides their widespread use for the treatment of a variety of peripheral inflammatory disorders such as atopic dermatitis, eczemas or arthritis in the horse, their surreptitious application has become a concern in doping cases in competition/performance horses. Assessing both basal and ACTH-stimulated plasma cortisol as well as basal ACTH concentrations following application of dexamethsone-containing dermal ointment is necessary to determine influences on hypothalamus-pituitary-adrenal (HPA) axis. Ten clinically healthy adult standardbred horses (6 mares, 4 geldings) were rubbed twice daily each with 50 g dexamethasone-containing ointment on a defined skin area (30 x 50 cm) for 10 days. RIA and chemiluminescent enzyme immuno-metric assay were used to determine resting and ACTH-stimulated plasma cortisol and basal ACTH concentrations, respectively. HPA feedback sensitivity and adrenal function were measured by a standard ACTH stimulation test. Dermal dexamethasone suppressed significantly the resting plasma cortisol level (to 75-98%) below baseline (P < 0.001) within the first 2 days and decreased further until day 10. ACTH stimulation test showed a markedly reduced rise in plasma cortisol concentrations (P < 0.001 vs. baseline). Plasma ACTH level decreased also during topical dexamethasone application. The number of total lymphocytes and eosinophil granulocytes was reduced, whereas the number of neutrophils increased. No significant change of serum biochemical parameters was noted. Dermal dexamethasone application has the potential to cause an almost complete and transient HPA axis suppression and altered leukocyte distribution in normal horses. The effects on HPA axis function should be considered in relation to the inability of animals to resist stress situations. The data further implicate that percutaneously absorbed dexamethasone (GCs) may cause systemic effects relevant to 'doping'.
Publication Date: 2009-07-21 PubMed ID: 19614843DOI: 10.1111/j.1365-2885.2008.01054.xGoogle Scholar: Lookup
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- Journal Article
Summary
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The research investigates the systemic effects of dexamethasone, a type of glucocorticoid, applied topically on horses, and it showed that such application could significantly affect the normal function of the hypothalamus-pituitary-adrenal (HPA) axis and alter leukocyte distribution.
Study Overview
- The study aimed to fill the knowledge gap about the effects of applying glucocorticoids, like dexamethasone, topically on horses.
- There are concerns that sneaky, topical application of glucocorticoids has been used for doping in horse competitions.
- The researchers investigated the changes in plasma cortisol and basal ACTH concentrations as a result of applying a dexamethasone-containing ointment to reveal the impacts on hypothalamus-pituitary-adrenal (HPA) axis function.
Methodology
- Ten healthy adult standardbred horses (6 mares, 4 geldings) were chosen for experimentation.
- Each of them had 50g of dexamethasone-containing ointment applied to a specific skin area twice daily for 10 days.
- The researchers utilized RadioImmunoAssay (RIA) and chemiluminescent enzyme immuno-metric assay for measuring resting and ACTH-stimulated plasma cortisol and basal ACTH concentrations respectively.
Results
- After just two days, the resting plasma cortisol level was suppressed significantly, falling to 75-98% below baseline, and this decreased further by day 10.
- The ACTH stimulation test exhibited a considerably reduced surge in plasma cortisol concentrations compared to the baseline.
- Topical application of dexamethasone also resulted in a decrease in plasma ACTH levels.
- There were alterations in cell distributions, the total number of lymphocytes and eosinophil granulocytes decreased, whereas the number of neutrophils increased.
- No significant changes were observed in serum biochemical parameters.
Conclusion
- The research concluded that topical application of dexamethasone can lead to almost complete and temporary HPA axis suppression and modify leukocyte distribution in healthy horses.
- This HPA axis suppression could result in the animal’s inability to manage stress situations.
- Further, the data suggests that dexamethasone absorbed through the skin can lead to systemic effects linked with doping.
Cite This Article
APA
Abraham G, Allersmeier M, Gottschalk J, Schusser GF, Hoppen HO, Ungemach FR.
(2009).
Effects of dermal dexamethasone application on ACTH and both basal and ACTH-stimulated cortisol concentration in normal horses.
J Vet Pharmacol Ther, 32(4), 379-387.
https://doi.org/10.1111/j.1365-2885.2008.01054.x Publication
Researcher Affiliations
- Institute of Pharmacology, Pharmacy and Toxicology, Faculty of Veterinary Medicine, Leipzig University, Leipzig, Germany. gabraham@rz.uni-leipzig.de
MeSH Terms
- Administration, Cutaneous
- Adrenocorticotropic Hormone / blood
- Animals
- Anti-Inflammatory Agents / administration & dosage
- Anti-Inflammatory Agents / blood
- Blood Chemical Analysis / veterinary
- Dexamethasone / administration & dosage
- Dexamethasone / blood
- Female
- Hematologic Tests / veterinary
- Horses / blood
- Hydrocortisone / blood
- Hypothalamo-Hypophyseal System / drug effects
- Hypothalamo-Hypophyseal System / metabolism
- Male
- Pituitary-Adrenal System / drug effects
- Pituitary-Adrenal System / metabolism
- Radioimmunoassay / veterinary
- Single-Blind Method
Citations
This article has been cited 1 times.- Vascellari M, Capello K, Stefani A, Biancotto G, Moro L, Stella R, Pozza G, Mutinelli F. Evaluation of thymus morphology and serum cortisol concentration as indirect biomarkers to detect low-dose dexamethasone illegal treatment in beef cattle.. BMC Vet Res 2012 Aug 3;8:129.
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