The therapeutic effect of a combination of cetirizine and pseudoephedrine compared to placebo is equivalent when tested in an environmental challenge chamber both within and out of the grass pollen season

Background: An Environmental Challenge Chamber (ECC) is a useful tool to expose allergic patients to relevant allergens in a controlled indoor setting and to test antiallergic treatments.Hitherto, ECC studies with grass pollen are primarily conducted offseason to avoid potential confounders. Therefore, the aim of this prospective study was to investigate whether the therapeutic effect of a combination of cetirizine and pseudoephedrine in an ECC setting is equivalent when tested within and out of the grass pollen season. Methods: In a randomised, double blind study the effect of a combination of 10mg cetirizine and 120 mg pseudoephedrine versus placebo on nasal symptoms, nasal secretion, and nasal flow measured by rhinomanometry was investigated in 70 patients with seasonal allergic rhinitis. Subjects underwent four 6h pollen exposures with Dactylis glomerata pollen in an ECC with drug administration after 2 h. Two exposures were conducted within the pollen season and two out of the pollen season. Results: The active treatment significantly reduced nasal symptoms, nasal secretion, and nasal flow compared to placebo both within and out of the pollen season (Po 0.0001). Treatment effects on symptoms, nasal secretion, and nasal flow were not different between the seasons. (P40.2, P40.5 P40.6, respectively). Conclusion: An ECC can be used to test anti-allergic treatments both within and out of the grass pollen season