Effect of desloratadine versus placebo on nasal airflow and subjective measures of nasal obstruction in subjects with grass pollen-induced allergic rhinitis in an allergen-exposure unit J Allergy Clin Immunol 109: 956-961

Background: Unlike many antihistamines, desloratadine can reduce nasal congestion in patients with seasonal allergic rhinitis (SAR). Objective: We compared the effects of 5 mg of desloratadine and placebo on nasal airflow and SAR symptoms, including nasal congestion, in response to grass pollen in an allergen-exposure unit. Methods: In a randomized, double-blind, placebo-controlled, crossover trial, 47 subjects with histories of SAR received desloratadine or placebo every morning for 7 days and, after a 10-day washout period, were crossed over to the other treatment arm for 7 days. Subjects underwent a 6-hour allergen exposure on day 7 of each treatment period. Nasal airflow and nasal secretion weights were measured before and every 30 minutes during allergen exposure; SAR symptoms (including nasal congestion) were scored before exposure and every 15 minutes thereafter. Results: Nasal obstruction, as measured by nasal airflow, was less severe with desloratadine than with placebo (P < .02). Individual and combined SAR symptom severity scores, including nasal congestion and sneezing, were significantly lower with desloratadine than with placebo (all P ≤ .003). Within 30 minutes of allergen exposure, less severely decreased nasal airflow (P < .02), less nasal secretions (P < .001), and less severe symptoms, including nasal congestion (P < .002), rhi-norrhea, and sneezing, occurred with desloratadine compared with placebo, and this continued throughout (0-6 hours) allergen exposure. Desloratadine was well tolerated, with an adverse event profile similar to that of placebo. Conclusion: In subjects with allergen-induced SAR symptoms, desloratadine significantly reduced the severity of nasal obstruction and accompanying complaints of nasal congestion and other SAR symptoms compared with the effects of placebo. (J Allergy Clin Immunol 2002;109:956-61.)