Effects of cyproheptadine and cetirizine on eosinophilic airway inflammation in cats with experimentally induced asthma.

OBJECTIVE To determine whether oral administration of cyproheptadine or cetirizine blocks the action of serotonin and histamine, respectively, and results in diminished eosinophilic airway inflammation in cats with experimentally induced asthma. ANIMALS 9 cats in which asthma was experimentally induced through exposure to Bermuda grass allergen (BGA) during a 3-month period. PROCEDURES Cats were randomized to receive monotherapy with each of 3 treatments for 1 week: placebo (flour in a gelatin capsule, PO, q 12 h), cyproheptadine (8 mg, PO, q 12 h), or cetirizine (5 mg, PO, q 12 h). A 1-week washout period was allowed to elapse between treatments. Prior to and following each 1-week treatment period, blood and bronchoalveolar lavage fluid (BALF) samples were collected. The percentage of eosinophils in BALF was evaluated to determine treatment efficacy. Serum and BALF BGA-specific immunoglobulin contents and plasma and BALF histamine concentrations were determined via ELISAs. Plasma and BALF serotonin concentrations were measured by use of a fluorometric method. RESULTS The mean +/- SD percentage of eosinophils in BALF did not differ significantly among treatment groups (placebo, 40 +/- 22%; cyproheptadine, 27 +/- 16%; and cetirizine, 31 +/- 20%). Among the treatment groups, BGA-specific immunoglobulin content and histamine and serotonin concentrations were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE In cats with experimentally induced asthma, cyproheptadine and cetirizine were not effective in decreasing airway eosinophilic inflammation or in altering several other measured immunologic variables. Neither cyproheptadine nor cetirizine can be advocated as monotherapy for cats with allergen-induced asthma.