Comparison of efficacy and tolerability of isoflupredone and dexamethasone in the treatment of horses affected with recurrent airway obstruction (‘heaves’).

This research aims to assess the relative performances of two corticosteroids, isoflupredone and dexamethasone, in the treatment of ‘heaves’ in horses, examining their effects on lung function, blood cortisol and electrolyte concentrations and response to ACTH stimulation. The study found that while both drugs are effective and well-tolerated, isoflupredone appears to decrease serum potassium levels, a side effect needing deeper investigation.

Methodology

• The researchers utilized a parallel design to evaluate the impacts of the two corticosteroids, isoflupredone acetate and dexamethasone, on horses suffering from heaves.
• Lung function, serum cortisol and electrolyte concentrations, haematology, and response to ACTH stimulation were analysed sequentially over a 14-day control period (no treatment), a 14-day treatment period, and a 7-day wash-out period.
• The dosages given were 0.03 mg/kg of Isoflupredone acetate via intramuscular injection to one group of six horses and 0.04 mg/kg of dexamethasone intravenously to another group of six horses.

Findings

• Both isoflupredone and dexamethasone were well tolerated and resulted in significant improvements in lung function.
• The improvement began around day three and persisted throughout the treatment and wash-out period.
• The corticosteroid treatment significantly decreased blood cortisol levels in both sets of horses. However, a normal response to ACTH stimulation was maintained.
• There were no observed changes in serum electrolyte concentrations in horses treated with dexamethasone. Conversely, horses treated with isoflupredone exhibited a significant drop in serum potassium levels.
• Both drug treatments induced stress-related changes in haematology.

Conclusion

• The study concluded that both isoflupredone and dexamethasone are effective for treating horses with heaves.
• However, isoflupredone is associated with hypokalaemia (low potassium levels in the serum), a side effect not observed in the dexamethasone-treated horses. Therefore, further research is warranted to investigate this side effect.