Background: Allergic rhinitis affects nearly one in 10 Ammericans. Cetirizine is a newerer once-daily selective H-1-antagonist. In traditional clinical trials, cetirizine has been shown to be safe and effective for the treatment of seasonal and perennial allergic rhinitis and chronic idiopatic urticaria. Objective: To better characterize the efficacy and onset of action of cetirizine in a more controlled but clinically relevant setting, this agent was compared with loratadine and placebo in patients with symptomatic seasonal allergic rhinitis undergoing controlled pollen chalenge in an environmental exposure unit (EEU). Methods: This was a double-blind, randomized, parallel-group study. After screening, patients were exposed to ragweed pollen (primed) in the EEU (up to six exposures), and those with qualifying symptom scores were randomized to controlled pollen exposure (two periods of 5.5 to 6.5 hours over 2 days) and once-daily treatment with 10 mg cetirizine (n = 67), 10 mg loratadine (n = 67), or placebo (n = 68). the mean ragweed pollen level was 3,480 +/- 350 grains/m(3) (standard deviation), the primary efficacy variables were the total symptom complex (TSC) and the major symptom complex (MSC) scores. Symptoms were evaluated every half hour in the EEU throughout the study. Results: Cetirizine produced a 36.7% mean reduction in TSC scores overall versus 15.4% with loratadine and 12.0% with placebo (p less than or equal to 0.01). Cetirizine also produced a 37.4% mean reduction in MSC scores overall versus 14.7% with loratadine and 6.7% with placebo (p less than or equal to 0.01). Onset of action as assessed by reductions in TSC and RISC scores versus placebo was evident within 1 hour with cetirizine (p less than or equal to 0.02) and 3 hours with loratadine (p less than or equal to 0.03). The incidence of treatment-related side effects was similar among groups, with headache reported most commonly in each group. Conclusions: Cetirizine is well tolerated and effective in reducing symptoms of seasonal allergic rhinitis in patients undergoing controlled pollen challenge.

Background: Azelastine solution is a topically (nasal) administered antiallergy drug with a preclinical profile suggestive of efficacy in patients with allergic rhinitis.