Effect of topical levocabastine on nasal response to allergen challenge and nasal hyperreactivity in perennial rhinitis

Background: It has been demonstrated that some oral antihistamines reduce nasal nonspecific reactivity and that topical levocabastine reduces cellular influx after nasal allergen challenge. This suggests that antihistamines possess other properties besides classical H₁-receptor antagonism. Objective: To evaluate the effect of 1 week's treatment with topical levocabastine on the nasal clinical response, inflammatory mediators, and nasal hyperreactivity. Methods: In a double-blind, placebo-controlled, 2- period, 2-treatment, crossover study, 21 rhinitic patients allergic to house dust mite participated. After each treatment period patients were challenged with house dust mite extract. Symptom scores and nasal lavages were collected for nine and one-half hours after challenge. Allergen-induced nasal hyperreactivity was determined by nasal methacholine challenge 24 hours after allergen challenge. A nasal histamine challenge was performed as well. Results: Patients showed only an immediate nasal response. Levocabastine significantly reduced the symptom score after 100 (P = .0063), 1000 (P = .0035), and 10,000 biological units (BU)/mL (P = .0013) of house dust mite extract. Albumin influx and tryptase release were not significantly reduced by levocabastine. No release of histamine and eosinophil cationic protein was seen. Levocabastine did not reduce nasal response to methacholine. Active treatment significantly reduced histamine-induced nasal secretion (P = .0009) and the number of sneezes (P = .0001). Conclusion: A significant effect of levocabastine was shown on the immediate clinical response to house dust mite and to histamine challenge only. Our findings suggest that levocabastine is an effective H₁-receptor antagonist without anti-inflammatory properties.