Prednisone per os is likely to have limited efficacy in horses.
Authors: Peroni D L, Stanley S, Kollias-Baker C, Robinson N E
Journal: Equine veterinary journal
Summary
# Editorial Summary When prednisone tablets became a standard recommendation for equine recurrent airway obstruction (heaves), the rationale seemed sound based on human asthma protocols; however, clinical outcomes suggested the drug was failing in horses, prompting Peroni and colleagues to investigate the pharmacokinetic mechanisms underlying this poor response. Using a crossover design in five horses, the researchers compared serum concentrations of prednisone and its active metabolite prednisolone following oral administration (tablets and liquid formulations), alongside intravenous prednisolone sodium succinate as a positive control, whilst measuring endogenous hydrocortisone suppression as a marker of biological activity. The critical finding was stark: prednisone tablets and liquid produced minimal serum prednisolone concentrations (detected in only one horse after tablet administration and absent entirely after liquid dosing), whereas prednisolone formulations were rapidly absorbed with peak serum levels within 45 minutes and demonstrated clear glucocorticoid suppression of endogenous hydrocortisone. This poor oral bioavailability of prednisone appears to result from inadequate gastrointestinal absorption and minimal hepatic conversion to the active prednisolone metabolite in equine patients. For practitioners, the practical implication is unambiguous: prednisone tablets should be abandoned in favour of prednisolone formulations if systemic corticosteroid therapy is indicated for heaves, as the commonly prescribed prednisone is unlikely to achieve therapeutic efficacy regardless of dosage.
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Practical Takeaways
- •Stop prescribing oral prednisone tablets or liquid for equine heaves; use prednisolone instead for reliable drug delivery and clinical effect
- •Prednisolone tablets achieve therapeutic serum levels within 45 minutes and demonstrate clear immunosuppression, making them the preferred oral corticosteroid choice
- •If oral corticosteroid therapy is required for recurrent airway obstruction, prednisolone formulations will provide the intended biological activity that prednisone cannot
Key Findings
- •Prednisone tablets and liquid showed poor absorption with minimal serum detection and rarely produced the active metabolite prednisolone
- •Prednisolone tablets and liquid were rapidly absorbed with peak serum concentrations within 45 minutes
- •Prednisolone suppressed endogenous hydrocortisone production, indicating biological activity, while prednisone did not
- •Prednisone has limited efficacy in horses due to poor absorption and failure to convert to the active metabolite prednisolone