Efficacy of salmeterol xinafoate in horses with recurrent airway obstruction

Objective-To determine the onset, magnitude, and duration of bronchodilation after administration of aerosolized salmeterol xinafoate in horses with recurrent airway obstruction. Design-Randomized controlled study Animals-6 horses with recurrent airway obstruction. Procedure-Horses received aerosolized salmeterol (210 mug) or no treatment, using a crossover design. Salmeterol was administered, using a mask designed for aerosol delivery in horses. Subjective rating of airway obstruction (RAO), maximal change in pleural pressure (Delta Ppl(max)), and pulmonary resistance (R-L) were determined at baseline; 5, 15, and 30 minutes; and 1, 2, 4, 6, 8, 10, and 12 hours after administration of salmeterol and in horses that did not receive treatment. Results-The Delta Ppl and R-L were improved 15 minutes through 6 hours after administration of salmeterol, compared with Values obtained from horses receiving no treatment. The RAO was improved 15 minutes through 2 hours after administration of salmeterol. The maximal response to salmeterol was evident 30 to 60 minutes after administration and was characterized by a 59 +/- 19% decrease in Delta Ppl and a 56 +/- 13% decrease in RL The Delta \Ppl and R-L were not different from baseline values 8 hours after salmeterol administration. Conclusions and Clinical Relevance-Duration of action of salmeterol in these horses was approximately 6 hours. Maximal bronchodilation was somewhat delayed (30 to 60 minutes), and the magnitude of response was similar to that of short-acting pp-adrenergic agonists. Salmeterol provides moderately sustained bronchodilation in horses with recurrent airway obstruction and may be an effective drug for long-term control of this condition.