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 parenteral administration of beclomethasone dipropionate and dexamethasone, respectively.


METHODS
6 horses with inducible and reversible heaves.


METHODS
Episodes of heaves were induced by exposure to moldy hay and straw for 7 days (natural challenge). Horses then underwent treatment (aerosolized beclomethasone, parenterally administered dexamethasone, and aerosolized propellant) for 7 days. Horses remained in the mold-contaminated environment for 7 days after discontinuation of drugs. Adrenocortical function was determine by serial evaluation of cortisol concentration in serum obtained on days 0, 7, 9, 12, 14, 16, 19, and 21. Adrenocorticotropic hormone stimulation testing was performed in 4 horses/treatment group on days 0, 7, 14, and 21.


RESULTS
Endogenous cortisol production was suppressed in beclomethasone- and dexamethasone-treated 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 significantly lower than baseline on days 14, 16, 19, and 21. Mean increase in serum cortisol concentration in response to ACTH stimulation testing after beclomethasone and dexamethasone administration did not differ significantly from the response observed in propellant-treated horses.


CONCLUSIONS
Aerosol and parenteral administration of beclomethasone and dexamethasone, respectively, suppressed adrenocortical function; however, endogenous cortisol production resumed approximately 2 and 4 days after discontinuation of drugs. Responsiveness to ACTH stimulation testing was not affected by the 7-day treatment period.
Rush
B R
BR
Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan 66506-5606, USA.
Worster
A A
AA
Flaminio
M J
MJ
Matson
C J
CJ
Hakala
J E
JE
D000280:Administration, Inhalation; D000302:Adrenal Cortex / Q000187:drug effects / Q000503:physiopathology*; D000324:Adrenocorticotropic Hormone; D000336:Aerosols; D000402:Airway Obstruction / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary*; D000821:Animal Feed; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000627:therapeutic use; D001507:Beclomethasone / Q000008:administration & dosage / Q000627:therapeutic use*; D018592:Cross-Over Studies; D003907:Dexamethasone / Q000008:administration & dosage / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D005516:Food Microbiology; D006734:Horse Diseases / Q000139:chemically induced / Q000188:drug therapy / Q000503:physiopathology*; D006736:Horses; D006854:Hydrocortisone / Q000097:blood*; D007275:Injections, Intravenous; D008297:Male; D012008:Recurrence; D013997:Time Factors
D000336:Aerosols; D000893:Anti-Inflammatory Agents; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D001507:Beclomethasone; D006854:Hydrocortisone