Endocrine effects of inhaled budesonide compared with inhaled fluticasone propionate and oral prednisolone in healthy Beagle dogs.

Orally administered corticosteroids are commonly used to treat chronic respiratory disease, but adverse effects suggest that the inhalation route may be safer. To compare the systemic effects of inhaled and oral corticosteroids, a prospective, randomised, placebo-controlled cross-over study was conducted. Six healthy neutered female Beagle dogs were randomly allocated to four treatment groups: (1) budesonide inhalation (200 μg twice daily); (2) fluticasone inhalation (250 μg twice daily); (3) oral prednisolone (1mg/kg once daily); and (4) placebo inhalation (room air twice daily). Each treatment and wash-out period lasted 4 weeks. The endocrine status of each dog was assessed on days 0, 28 and 35 using the adrenocorticotropic hormone (ACTH) stimulation test. The effects of treatments were assessed using a linear mixed effects model. After the 4 week treatment period, a significant decrease was observed in the basal serum cortisol level of the prednisolone group (P<0.03), and a decrease was also seen in the ACTH-stimulated peak cortisol levels of both the prednisolone and fluticasone groups (P<0.001), compared with the budesonide group in which no suppression was detected. The results showed that cortisol production in dogs was strongly suppressed by oral prednisolone and by inhaled fluticasone.