A randomized, masked, crossover, clinical trial of the efficacy and safety of nebulized albuterol sulfate and dexamethasone sodium phosphate in asthmatic horses.

Nebulized dexamethasone is ineffective for severe equine asthma despite adequate lung deposition.

This randomized, masked, crossover clinical trial evaluated nebulized dexamethasone sodium phosphate (DSP) combined with albuterol bronchodilation in seven horses with severe equine asthma (SEA). The study compared three treatments: IV DSP (0.04 mg/kg), nebulized DSP (0.01 mg/kg), and nebulized DSP (0.02 mg/kg), administered daily for 7 days using a 3×3 Latin square design. All nebulized DSP groups received albuterol (0.3 μg/kg) 10 minutes prior to dexamethasone administration to improve lung deposition. Outcome measures included clinical scoring, pulmonary function testing, bronchoalveolar lavage fluid cytology, adrenocorticotropic hormone stimulation, plasma and BALF drug concentrations, and hematologic parameters. Results demonstrated that nebulized DSP achieved lung deposition comparable to IV administration while avoiding systemic adrenocortical suppression. However, nebulized DSP failed to improve clinical signs, pulmonary function, or BALF neutrophil proportions. Only IV DSP produced improvements in lung function. These findings suggest that despite minimizing systemic absorption, nebulized DSP at the tested doses is ineffective for treating SEA, limiting its clinical application in equine respiratory disease management.

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