Effects of fluticasone propionate dosage in an experimental model of feline asthma

Abstract

Cats with inflammatory bronchial disease are usually treated with glucocorticoid (GC) drugs to reduce airway inflammation. Inhalant GC delivery can preserve airway effects while systemic effects are minimized. An appropriate dosage regimen for inhaled GC in cats has not been investigated. A blinded, randomized, cross-over study design was used to investigate the ability of three different dosages of the inhalant GC fluticasone propionate delivered by metered dose inhaler to ameliorate eosinophilic airway inflammation in cats with experimentally induced allergic airway inflammation. Further, suppression of the hypothalamic-pituitary-adrenal axis (HPAA) at each dose was assessed. Fluticasone administered at dosages of 44, 110, or 220 microg q 12h reduced airway eosinophilia by 74%, 82%, or 81%, respectively (no difference). None of the dose regimens tested caused HPAA suppression. We conclude that a twice daily dosage of 44 microg fluticasone should be evaluated for the management of cats with naturally occurring inflammatory bronchial disease.

Fig 1.

ACTH stimulation test results before and after 3 weeks of treatment with three, twice daily dose regimens of fluticasone propionate delivered by pMDI. There were no significant differences in stimulated (peak minus pre-cortrosyn) cortisol concentrations prior to any of the 3 week courses of therapy (44, 110, or 220 μg fluticasone q 12 h). Additionally, stimulated cortisol concentrations did not change significantly after the 3 week course of therapy at any dosage (44 μg, P=0.144; 110 μg, P=0.592; 220 μg, P=0.534).

Fig 2.

Morning cortisol before and after 3 weeks of treatment with three, twice daily dose regimens of fluticasone propionate delivered by pMDI. No difference was detected between groups in morning cortisol prior to GC treatment. When morning cortisol after the 3 week treatment period was compared to morning cortisol prior to treatment, there were no significant differences in cats receiving either 44 μg or 220 μg fluticasone q 12 h (P=0.599 and 0.937, respectively). Morning cortisol was significantly increased after 3 weeks of treatment with 110 μg fluticasone q 12 h (*P=0.025).

Fig 3.

BALF eosinophilia in cats before and after 3 weeks of treatment with three, twice daily dose regimens of fluticasone propionate delivered by pMDI. The percentage of eosinophils among all cell types within the airway lavage fluid decreased significantly (*) after a 3 week course of treatment with twice daily fluticasone at 44 μg (P=0.034), 110 μg (P=0.018), and 220 μg (P=0.009) fluticasone q 12 h.