PULMONARY-FUNCTION IN HORSES WITH RECURRENT AIRWAY-OBSTRUCTION AFTER AEROSOL AND PARENTERAL ADMINISTRATION OF BECLOMETHASONE DIPROPIONATE AND DEXAMETHASONE, RESPECTIVELY

Objective-To determine changes in clinical signs of disease and respon se to pulmonary function testing in horses with recurrent airway obstr uction (heaves) after aerosol and parenteral administration of beclome thasone dipropionate and dexamethasone, respectively. Animals-6 horses with inducible and reversible heaves. Procedure-Episodes of heaves we re induced by exposure (challenge) to moldy hay and straw for 7 days. Horses were assigned to treatment groups (aerosolized beclomethasone d ipropionate, parenterally administered dexamethasone, aerosolized prop ellant [control]), and respiratory frequency and subjective assessment of respiratory effort were determined twice daily. Maximal change in pleural pressure (Delta-Ppl(max)), pulmonary resistance (R-L), and dyn amic compliance (C-dyn) was determined on days 0, 7, 10, 14, and 21. R esults-The R-L and Delta Ppl(max) were increased, and C-dyn was decrea sed in all horses in response to natural challenge. Beclomethasone red uced R-L on day 10, reduced Delta Ppl(max) on days 14 and 21 and incre ased C dyn on day 14. Dexamethasone reduced R-L and Delta Ppl(max) on days 10, 14, and 21 and increased C-dyn on days 10 and 14, Respiratory effort (subjective assessment) improved after 2 and 3 days of beclome thasone and dexamethasone administration but rebounded to pretreatment values 1 and 3 days after discontinuation of drugs. Conclusions-Pulmo nary function testing responses and clinical signs of airway obstructi on were improved by administration of beclomethasone. The magnitude of response to aerosolized beclomethasone generally was less marked than the response to parenterally administered dexamethasone. Higher or mo re frequent dosing of aerosolized beclomethasone may be necessary to a chieve the anti-inflammatory response to parenterally administered dex amethasone.