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

Objective-To determine alteration in adrenocortical function in horses with recurrent airway obstruction (heaves) after aerosol and parenter al administration of beclomethasone dipropionate and dexamethasone, re spectively. Animals-6 horses with inducible and reversible heaves. Pro cedure-Episodes of heaves were induced by exposure to moldy hay and st raw for 7 days (natural challenge). Horses then underwent treatment (a erosolized beclomethasone, parenterally administered dexamethasone, an d aerosolized propellant) for 7 days. Horses remained in the mold-cont aminated environment for 7 days after discontinuation of drugs. Adreno cortical function was determined by serial evaluation of cortisol conc entration in serum obtained on days 0, 7, 9, 12, 14, 16, 19, and 21. A drenocorticotropic hormone stimulation testing was performed in 4 hors es/treatment group on days 0, 7, 14, and 21. Results-Endogenous cortis ol production was suppressed in beclomethasone- and dexamethasone-trea ted horses within 2 days of treatment but recovered to values similar to those in propellant-treated horses approximately 2 and 4 days after discontinuation of drugs. Serum cortisol concentration in propellant- treated horses gradually decreased during the study and was significan tly lower than baseline on days 14, 16, 19, and 21. Mean increase in s erum cortisol concentration in response to ACTH stimulation testing af ter beclomethasone and dexamethasone administration did not differ sig nificantly from the response observed in propellant-treated horses. Co nclusions-Aerosol and parenteral administration of beclomethasone and dexamethasone, respectively, suppressed adrenocortical function; howev er, endogenous cortisol production resumed approximately 2 and 4 days after discontinuation of drugs. Responsiveness to ACTH stimulation tes ting was not affected by the 7-day treatment period.