Sodium retention and cortisol (hydrocortisone) suppression caused by dexamethasone and triamcinolone in equids.

This research explored the effects of two drugs, dexamethasone and triamcinolone, on sodium retention and cortisol suppression in horses and ponies. It found that these drugs caused changes in serum electrolytes and urinary excretion, as well as a maximal cortisol suppression within 12 hours, lasting different durations for each drug.

Objective of the Study

The study aimed to examine how dexamethasone (DXM) and triamcinolone (TMC) affect sodium retention and the suppression of cortisol, also known as hydrocortisone, in horses and ponies.

Methods of the Study

• Three ponies and one horse underwent a bilateral adrenalectomy (BADX). The subsequent low adrenal condition was reversed using DXM or TMC.
• The researchers studied the influence of these drugs on changes in serum electrolytes and urinary excretion to determine sodium and chloride retention and potassium expulsion.
• Eight additional adult horses were divided into two groups and given a single injection of DXM or TMC. These groups were used to observe the effect of the drugs on cortisol suppression.

Findings of the Study

The study yielded several key findings:

• Cortisol suppression was maximal (no detectable amounts of cortisol) within 12 hours of administering DXM or TMC.
• The DXM group had detectable cortisol amounts 24 hours after injection, returning to pre-injection levels after a week (168 hours).
• In contrast, the TMC group didn’t show detectable cortisol levels for 192 hours and took two weeks (336 hours) to return to pre-injection levels.
• It was also noted that the period of the gluconeogenic effect (production of glucose) aligns with the respective duration of cortisol suppression by each steroid. This established a relative low adrenal state in animals treated with DXM between the 2nd and 7th day, and between the 6th and 14th day in the TMC group.

Conclusion of the Study

The research demonstrated that DXM and TMC cause considerable changes in serum electrolytes, urinary excretion, and suppress the secretion of cortisol to undetectable levels within 12 hours. Both drugs produced a distinct low adrenal condition in animals, although the duration varied between the drugs. These findings provide valuable insights into the physiological responses of horses and ponies to these steroids and prove helpful for targeted therapeutic applications.