Prednisone per os is likely to have limited efficacy in horses.

This research study tested the effectiveness of the corticosteroid prednisone for treating recurrent airway obstruction in horses. Using a crossover study with five horses, the researchers found that both prednisone tablets and liquid were poorly absorbed in the body and did not significantly produce the active metabolite, prednisolone. Conversely, prednisolone tablets were rapidly absorbed and proved effective, indicating potential use for treating this condition in horses.

Objective of the Research

• The main purpose of this research was to study the efficacy of the corticosteroid prednisone in treating recurrent airway obstruction (commonly known as ‘heaves’) in horses. Though prednisone has been found to be effective in treating human asthma, it was observed to have limited effectiveness for treating similar symptoms in horses. The researchers wanted to understand why.

Methodology

• A crossover study was conducted involving five horses which received various treatments such as prednisone tablets and liquid, prednisolone tablets and liquid, and prednisolone sodium succinate, administered intravenously.
• Blood samples were taken from the horses before treatments and at selected points over a 24-hour period to check for the present concentrations of prednisone, prednisolone and the endogenous glucocorticoid hydrocortisone.

Findings

• The study found that while prednisolone in both tablet and liquid form were quickly absorbed with detectable serum concentrations within 15 minutes of administration, only small amounts of prednisone were detected in the serum samples post administration of prednisone tablets and liquid.
• Prednisolone was not produced significantly in the body following the administration of oral prednisone. This implies that the metabolism of prednisone into its active form, prednisolone, is limited.

Conclusion

• The research concluded that prednisone has low efficacy in the treatment of heaves in horses due to its poor absorption and its limited conversion into the active form, prednisolone.
• On the contrary, prednisolone tablets showed excellent bioavailability indicating that they could be a useful therapeutic agent against heaves in horses.