Histamine and tryptase in nasal lavage fluid after allergen challenge: Effect of 1 week of pretreatment with intranasal azelastine or systemic cetirizine

Background: Antihistamines (H-1-receptor antagonists) act by competitive an tagonism of histamine at H-1-receptors, In addition, high concentrations of some antihistamines inhibit allergen-induced histamine release from mast c ells in vitro, Objective: The purpose of this study was to determine the effect of intrana sal azelastine or systemic cetirizine (both potent antihistamines) on the a llergen-induced release of mast-cell mediators from the human nasal mucosa in vivo. Methods: Patients allergic to birch pollen (n = 11)and control subjects not allergic to birch pollen (n = 5) were included in a randomized, double-bli nd, placebo-controlled, 3-way crossover study outside the pollen season. Ea ch subject was treated with azelastine nasal spray 0.14 mg per nostril twic e daily, cetirizine tablets 10 mg every day, or placebo for 1 week using a double-dummy design. At the end of each treatment period, nasal allergen ch allenges were performed, and the number of sneezes were counted. In additio n, nasal lavage fluid was collected, and the-levels of mast-cell mediators (histamine and tryptase) were measured. Results: The allergen challenge of patients allergic to pollen produced sne ezing and a significant increase in the Levels of histamine and tryptase. T he challenge of subjects not allergic to pollen produced no such response. Azelastine and cetirizine significantly reduced allergen-induced sneezing a nd the associated increase in histamine and tryptase levels. No significant differences were found between the azelastine and cetirizine treatments. Conclusion: Pretreatment with azelastine or cetirizine inhibits the allerge n-induced release of mast-cell mediators from the human nasal mucosa, Our r esults are consistent with the hypothesis that both antihistamines reduce m ediator release from nasal mucosa mast cells in vivo. However, further stud ies are necessary to test this hypothesis.