Pulmonary function in horses with recurrent airway obstruction after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively

Abstract

Objective - To determine changes in clinical signs of disease and response to pulmonary function testing in horses with recurrent airway obstruction (heaves) after aerosol and parenteral administration of beclomethasone dipropionate and dexamethasone, respectively. Animals - 6 horses with inducible and reversible heaves. Procedure - Episodes of heaves were induced by exposure (challenge) to moldy hay and straw for 7 days. Horses were assigned to treatment groups (aerosolized beclomethasone dipropionate, parenterally administered dexamethasone, aerosolized propellant [control]), and respiratory frequency and subjective assessment of respiratory effort were determined twice daily. Maximal change in pleural pressure (Δ-Ppl(max)), pulmonary resistance (R(L)), and dynamic compliance (C(dyn)) was determined on days 0, 7, 10, 14, and 21. Results - The R(L) and ΔPpl(max) were increased, and C(dyn) was decreased in all horses in response to natural challenge. Beclomethasone reduced R(L) on day 10, reduced ΔPpl(max) on days 14 and 21 and increased C(dyn) on day 14. Dexamethasone reduced R(L) and ΔPpl(max) on days 10, 14, and 21 and increased C(dyn) on days 10 and 14. Respiratory effort (subjective assessment) improve after 2 and 3 days of beclomethasone and dexamethasone administration but rebounded to pretreatment values 1 and 3 days after discontinuation of drugs. Conclusions - Pulmonary function testing responses and clinical signs of airway obstruction were improved by administration of beclomethasone. The magnitude of response of aerosolized beclomethasone generally was less marked than the response to parenterally administered dexamethasone. Higher or more frequent dosing of aerosolized beclomethasone may be necessary to achieve the anti-inflammatory response to parenterally administered dexamethasone.