Effects of fexofenadine on the early response to nasal allergen challenge

Background: Previous studies using nasal allergen challenge models have shown that terfenadine, an H-1 antihistamine, inhibits histamine release during the early response to allergen provocation. Fexofenadine, the active metabolite of terfenadine, has strong H-1-antihistaminic activity and no cardiac effects. Clinical studies have documented the efficacy of fexofenadine in the treatment of allergic rhinitis. Objective: To determine whether fexofenadine, like terfenadine, inhibits histamine and tryptase release during the early allergic response. Methods: Randomized, double blind, placebo-controlled, two-way crossover study in 20 subjects with seasonal allergic rhinitis, out of their allergy season (median age 27.5 years, 13 males and 7 females). Subjects were medicated with either placebo or fexofenadine 180 mg orally daily for 1 week followed by nasal challenge with allergen. After each challenge, sneezes and nasal symptoms were recorded, and a nasal lavage was obtained for the assay of albumin, an indicator of vascular permeability, and histamine and tryptase, indicators of mast cell degranulation. Results: When patients were on placebo, allergen challenges led to significant increases in all measured parameters compared with the sham challenges with diluent. Treatment with fexofenadine resulted in inhibition of allergen-induced symptoms and increased vascular permeability, but not the release of histamine and tryptase. Conclusion: Fexofenadine is an effective H-1 antihistamine, but in contrast to its parent compound, terfenadine, it does not affect the release of the mast cell mediators histamine and tryptase.