Background: Equine recurrent airway obstruction (RAO) is characterized by airway inflammation, bronchoconstriction, and increased mucus production in the airways. Anticholinergic drugs like atropine induce bronchodilatation and rapid improvement in lung function. N-butylscopolammonium bromide (NBB) is an anticholinergic drug used to relieve spasmodic colic in horses, but its effect on airway smooth muscle is unknown.Objective: To evaluate the effect of NBB on clinical signs and lung function of RAO-affected horses. Animals: Nine horses diagnosed with RAO. Methods: Double-blind, placebo-controlled, randomized crossover trial. Horses were challenged with moldy hay until a maximum change in transpulmonary pressure (ΔP Lmax ) > 15 cmH 2 O was achieved. NBB (0.3 mg/kg) or placebo (0.9% saline) was administered IV. Clinical scores and lung function were recorded at baseline and then periodically after treatment administration. Horses were allowed a 6-week washout before administration of opposite treatments.Results: Clinical score at 10 and 30 minutes (8.7 ± 2.8 and 8.7 ± 3.2, respectively) after NBB administration was significantly lower than baseline (10.8 ± 2.4). NBB administration resulted in a significant decrease in ΔP Lmax (baseline: 35.1 ± 6.9 cmH 2 O) starting 2 minutes after administration (16.3 ± 6.6 cmH 2 O) with a maximum decline observed at 10 minutes (13.5 ± 7.1 cmH 2 O). ΔP Lmax values between 60 and 120 minutes after NBB administration were not different from placebo.Conclusion and Clinical Importance: N-butylscopolammonium bromide is a potent bronchodilator, reaching maximum effect 10 minutes after intravenous administration. This effect dissipates within 1 hour of drug administration.

Background: One proposed nonmedical therapy for recurrent airway obstruction (RAO) in horses is a handheld acoustic device that propels sound waves from the nose down the tracheobronchial tree where it is intended to dislodge mucous and relax bronchospasm, permitting clearance of mucoid secretions.Objective: To evaluate the effectiveness and safety of this device when used as per the manufacturer's recommendations as a treatment for RAO.Animals: Nine adult horses previously diagnosed with RAO. Methods: Prospective, cross-over clinical trial. Horses were exposed to a dusty environment until airway obstruction developed as defined by standard lung mechanics (SLM). Horses were randomly assigned to receive either acoustic therapy or a sham treatment for 4 weeks while being maintained in this environment. Horses were evaluated by clinical scores, SLM, and forced expiration regularly for 4 weeks. The opposite treatment was administered after a washout period.Results: Seven horses received the treatment; 9 received the sham. There were no changes (P 4 .05) in clinical score, maximal change in transpulmonary pressure (DP Lmax ), lung resistance (R L ), or the forced expiratory flow rate averaged over the last 75-95% of expiration (FEF 75À95% ) over the study period. The device was determined to be safe, although several minor adverse effects were noted, including head tossing, coughing, and chewing during treatment.Conclusions and Clinical Importance: Treatment with this device did not improve clinical signs or lung function in horses with RAO kept in a dusty environment. Currently accepted treatments, including environmental management and medical therapy, should be recommended.