Comparison of the effects of desloratadine 5-mg daily and placebo on nasal airflow and seasonal allergic rhinitis symptoms induced by grass pollen exposure

Background: Nasal congestion is a chronic symptom of seasonal allergic rhinitis (SAR) that is often difficult to treat with antihistamines. Desloratadine, a new, potent, H-1 -receptor antagonist has been shown to decrease nasal congestion in clinical trials and to maintain nasal airflow in response to grass pollen exposure. We compared the effects of desloratadine 5 mg and placebo on nasal airflow, nasal secretion weights and SAR symptoms, including nasal congestion, in patients exposed to grass pollen in an environmental exposure unit. Methods: Forty-six grass pollen allergic SAR patients received desloratadine or placebo for 7 days, followed by a 10-day washout, and then crossed over to the other treatment for 7 days. A 6-h allergen exposure was performed at the end of each treatment period. Results: Desloratadine was significantly superior to placebo in maintaining nasal airflow (P less than or equal to 0.014) and lessening the increase in nasal secretion weights (P < 0.001) throughout allergen exposure. SAR symptom scores, including nasal congestion, were significantly less with desloratadine than placebo (P less than or equal to 0.001). Desloratadine was well tolerated. Conclusions: This study confirms that, compared with placebo, desloratadine can maintain nasal airflow and reduce nasal secretion weights and the severity of SAR symptoms, including nasal congestion, in SAR patients exposed to grass pollen allergen.