Objective—To evaluate clinical response, pulmonary
function, and adrenal gland response to incremental
doses of beclomethasone dipropionate in horses with
recurrent airway obstruction.
Animals—8 horses with recurrent airway obstruction.
Procedure—Horses randomly assigned to 4 groups
were treated twice daily via aerosol administration of
placebo or 500, 1,000, or 1,500 µg of beclomethasone
dipropionate in a crossover design with a 10-day
minimum washout period. Subjective assessment of
airway obstruction, serum cortisol concentration, and
maximum change in pleural pressure during tidal
breathing (ΔPplmax) were determined daily prior to
morning drug administration, and ΔPplmax was reevaluated
15 minutes after morning drug administration.
Pulmonary resistance and dynamic compliance were
determined at baseline and approximately 12 hours
after the final treatment.
Results—An immediate treatment effect was not
identified. Within 24 hours, ΔPplmax and airway
obstruction were lower in horses receiving
beclomethasone. Onset and magnitude of response
was similar among the 3 beclomethasone dose regimens.
Pulmonary resistance was improved only after
administration of all 3 doses of beclomethasone,
whereas dynamic compliance was improved after
administration of 1,000 µg and 1,500 µg of
beclomethasone. Reduction in serum cortisol concentration
occurred with all 3 beclomethasone dose
regimens; however, the magnitude of adrenal gland
suppression was greater in horses receiving 1,000 or
1,500 µg of beclomethasone.
Conclusions and Clinical Relevance—Low-dose
(500 µg) beclomethasone administration caused similar
improvement in pulmonary function, compared
with high-dose beclomethasone (1,000 and 1,500
µg), with the exception of dynamic compliance, and
caused less suppression of endogenous cortisol production.
(J Am Vet Med Assoc 2000;217:359–364)