Effect of levocabastine, a new H1 antagonist, in a conjunctival provocation test with allergens.

Levocabastine is a new, highly potent, and specific H1 antagonist. The effects of this drug, administered topically, were evaluated in a conjunctival provocation test (CPT) with allergens. CPT was performed by the instillation of one drop of allergen at increasing concentrations in the inferior conjunctival sac of each eye, alternatively, and stopped when both itching and redness of the conjunctiva were present. The concentration of allergen at this step was considered as the reaction threshold. Eleven patients, allergic to grass pollen, underwent, in winter, a first CPT without pretreatment (screening test); the CPT was then repeated twice after a 24-hour treatment, once, with a placebo, and once, with levocabastine (one drop twice a day, 0.5 mg/ml), administered in a double-blind fashion and in random order. The minimal interval between the two tests was 1 week. There was no significant difference between the thresholds determined in the two CPTs performed without medication (screening test and placebo), whereas the threshold was significantly increased (p less than 0.001) after pretreatment with levocabastine. Individually, the threshold increased in 10/11 patients (p less than 0.01). Levocabastine prevented both redness and itching. A late allergic reaction was observed by the patient in 6/11 CPTs performed after placebo treatment and 8/11 after levocabastine treatment. We conclude that, in this model of allergic conjunctivitis, levocabastine increased the conjunctival tolerance to an allergen. Further studies should help to determine the true place of this H1 antagonist in the treatment of allergic conjunctivitis.