Onset of action of loratadine/montelukast in seasonal allergic rhinitis subjects exposed to ragweed pollen in the Environmental Exposure Unit.

Onset of action is recognized as an important pharmacologic property of allergic rhinitis (AR) medications. This study was designed to evaluate the onset of action of loratadine/montelukast (L/M; 10 mg/10 mg) versus placebo in subjects with ragweed-induced seasonal AR (SAR). A single-center, double-blind, parallel-group study of ragweed-sensitive AR subjects (n = 310) was performed in the Environmental Exposure Unit (EEU). Subjects were exposed to ragweed pollen in the EEU and symptoms were recorded at 30, 60, 90, and 120 minutes before a single dose of L/M or placebo. After dosing, symptoms were recorded for 4 hours, at 15-minute intervals for the first 2 hours and at 30-minute intervals for the final 2 hours. The primary end point was time to onset of action of L/M, defined as the first time point at which the mean change from baseline in total symptom score (TSS) for L/M became and remained significantly better than placebo. Secondary end points included nasal congestion scores and peak nasal inspiratory flow (PNIF). The onset of action of L/M for TSS was 1 hour and 15 minutes (p = 0.005 versus placebo). L/M reduced nasal congestion as indicated by significant improvements in both the nasal congestion score (p = 0.011) and the PNIF measurements (p = 0.007) within 1 hour and 15 minutes postdose. The incidence of treatment-emergent adverse events was similar between groups. The onset of action after treatment with L/M was 1 hour and 15 minutes for TSS, as well as nasal congestion. L/M was well tolerated.