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

backgroundNebulization of injectable dexamethasone sodium phosphate (DSP; 0.01 mg/kg) to horses with severe equine asthma (SEA) was previously found to be ineffective. Horses with SEA have marked bronchoconstriction that decreases peripheral lung deposition of nebulized drugs. Administration of a bronchodilator immediately before nebulizing dexamethasone may improve efficacy. HYPOTHESIS/

objectivesEvaluate the therapeutic effects and optimal dose of nebulized DSP after nebulized albuterol in horses with SEA. ANIMALS: Seven horses with SEA from a research herd.

methodsIn this masked randomized crossover trial, horses were assigned to one of 3 treatment groups: (1) 0.04 mg/kg DSP IV; (2) 0.01 mg/kg DSP by nebulization; and (3) 0.02 mg/kg DSP by nebulization, in a 3 × 3 Latin square design. All horses were treated q24h for 7 days and received albuterol (0.3 μg/kg) 10 min before DSP. Clinical score, pulmonary function testing, bronchoalveolar lavage fluid (BALF) cytology, adrenocorticotropic hormone stimulation test, plasma and BALF DSP concentrations and routine blood test results were compared between groups and over time.

resultsNebulized DSP resulted in similar lung deposition as IV DSP but did not suppress adrenocortical function. However, nebulized DSP did not improve clinical signs, lung function, or BALF cytology. Only IV DSP improved lung function. None of the treatments performed influenced BALF neutrophil proportions. CONCLUSIONS AND CLINICAL IMPORTANCE: Nebulization of albuterol before DSP minimizes systemic absorption of dexamethasone and preserves adrenal function of horses with SEA. Our results do not support the use of nebulized DSP at the doses used for the treatment of SEA.