Comparative onset of action and symptom relief with cetirizine, loratadine, or placebo in an environmental exposure unit in subjects with seasonal allergic rhinitis: confirmation of a test system

Abstract

The environmental exposure unit (EEU) is an instrument designed to determine onset of action of antiallergic treatment. Confirmation of test results would be useful in defining its role. This study was intended to confirm a previous study comparing cetirizine, loratadine, and placebo in the EEU using an identical protocol design (randomized, double-blind, parallel-group comparison having the same symptom scoring system, endpoints, and statistical analyses), thus demonstrating reproducibility of studies conducted in the EEU. Onset of action and symptom relief with once-daily cetirizine 10 mg, loratadine 10 mg, and placebo (n = 120 each group) were evaluated replicating a previous study design. Subjects meeting inclusion and exclusion criteria and qualifying symptom scores were randomized to 2 days' exposure (6 to 7 hours daily) with treatment. Changes in total and major symptom complex (TSC, MSC) scores based on 14 symptoms evaluated at 30-minute intervals served as primary efficacy variables. Onset of action again was earlier with cetirizine (at 1 hour, P < or = 0.001) versus loratadine (at 3 hours, P < or = 0.01). Cetirizine produced a 25.4% least-square mean reduction in TSC scores overall versus an 11.2% decrease with loratadine (P = 0.006) and a 4.8% increase with placebo (P < 0.001); loratadine and placebo were also significantly different (P = 0.002). Similar changes were also noted in MSC scores. Cetirizine consistently reduced TSC and MSC scores after the first dose versus placebo (P < or = 0.001) and at most time points versus loratadine (P < or = 0.05). Adverse events were reported in 1.7% of patients in each active-treatment group and in 2.5% on placebo. Cetirizine acted earlier and was more effective than loratadine or placebo in reducing symptoms of seasonal allergic rhinitis in subjects undergoing a controlled pollen challenge, replicating results from an earlier, identically designed study, demonstrating reproducibility of these assessments by the EEU.