Onset of action of loratadine/montelukast combination in subjects with seasonal allergic rhinitis in the environmental exposure unit

Methods A single-center, double-blind, parallel-group study of ragweed-sensitive allergic rhinitis subjects (N=310), performed in the EEU. Subjects were exposed to ragweed pollen in the EEU and symptoms were recorded at 30, 60, 90, and 120 minutes prior to a single dose of loratadine/montelukast or placebo. After dosing, symptoms were recorded for 4 hours at 15-minute intervals for the first 2 hours and 30-minute intervals for the final 2 hours. The primary endpoint was the time to onset of action for loratadine/montelukast, defined as the first time point at which the mean change from baseline in total symptom score (TSS) for loratadine/montelukast became and remained significantly better than placebo. Secondary endpoints included nasal congestion scores and peak nasal inspiratory flow (PNIF).