Dose Effects of Fluticasone Propionate in an Experimental Model of Feline Asthma
Feline asthma is an inflammatory lower airway disorder affecting up to 1% of cats. Treatment relies on administration of corticosteroids; inhaled corticosteroids may result in control of airway inflammation with fewer systemic effects than oral or injectable preparations. Currently, there is no evidence as to the appropriate dose of inhaled corticosteroid to control airway inflammation in cats. The goal of this research was to compare efficacy of 44 µg, 110 µg, or 220 µg fluticasone propionate delivered by inhalation twice daily for 21 days on eosinophilic airway inflammation in cats with experimentally-induced asthma. We hypothesized that the 44 µg would control airway inflammation equally as well as higher dosage formulations.
Six kittens were sensitized to Bermuda grass allergen to create an asthmatic phenotype; a minimum of >15% eosinophils on airway lavage was documented prior to treatment. Cats were randomized to one of three treatment groups, and then received the fluticasone dose appropriate for the group (44 µg, 110 µg, or 220 µg) twice daily for 21 days. Evaluation included bronchoalveolar lavage (BAL) with enumeration of eosinophils at baseline and after completion of the 21 day treatment. After a four week wash-out period, cats were crossed-over to another dose group, and the procedures repeated until each cat had received all three dose regimens. Results were expressed as means ± SD. Base line treatments were compared by ANOVA. Pre and post treatment eosinophil percentage was compared via paired T-test.
Usable data was obtained for only 5 cats for the 44 µg and 220 µg dose due to either inadequate baseline eosinophilia or poor sampling. Airway eosinophils were not different between dose treatment groups at baseline (p=0.225; 44 µg dose 25.5 ± 14.4% eos; 110 µg dose 41.0 ± 26.8% eos; 220 µg dose 22.3 ± 12.7% eos). After treatment, airway eosinophilia was reduced in all treatment groups as compared to pre-treatment values (44 µg dose 6.6 ±4.6% p = 0.021; 110 µg dose 8.3 ± 9.2% p = 0.018; 220 µg dose 4.8 ± 4.1% p = 0.01). In conclusion, it appears that all three dosages (44, 110, and 220 µg/cat BID) of inhaled fluticasone were able to significantly diminish airway eosinophilia. Studies should be performed to evaluate clinical efficacy of 44 µg/cat BID fluticasone in cats with naturally occurring feline bronchopulmonary disease.