Randomized, double-masked, placebo-controlled comparison of the efficacy of emedastine difumarate 0.05% ophthalmic solution and ketotifen fumarate 0.025% ophthalmic solution in the human conjunctival allergen challenge model

Background: Emedastine difumarate 0.05% ophthalmic solution and ketotifen fumarate 0.025% ophthalmic solution are 2 topical antiallergic agents available in the United States and other countries. Emedastine is indicated for the temporary relief of the signs and symptoms of allergic conjunctivitis. Ketotifen is indicated for the temporary relief of ocular itching caused by allergic conjunctivitis. Objective: The purpose of this study was to compare the efficacy of these agents in the temporary relief of ocular itching due to allergic conjunctivitis. The 2 agents were compared with each other and with placebo (artificial tears) using the conjunctival allergen challenge (CAC) model. Methods: This was a single-center, randomized, double-masked, placebo-controlled study. At visit 1, CAC was performed on eligible subjects to identify the dose required to elicit a positive allergic reaction. Subjects returned after 7 days for visit 2 to confirm the allergen dose. On day 14 ( 3) of the study, enrolled subjects were randomized to I of 3 treatment groups: emedastine in I eye and placebo in the other, ketotifen in 1 eye and placebo in the other, or emedastine in 1 eye and ketotifen in the other. In 25 subjects, bilateral CAC was performed 5 minutes after study medication instillation. In a second group of 20 subjects, CAC was performed 15 minutes after medication instillation. Itching was graded according to a standardized 5-point scale (0 = none to 4 = severe itching) at 3, 5, and 10 minutes postchallenge. Differences in efficacy scores between treatments and versus placebo were compared using 2-sample t tests of equal variance. Results: A total of 45 patients (mean age, 41.2 years) received treatment: 16 received emedastine in 1 eye and ketotifen in the other; 14 received emedastine in 1 eye and placebo in the other; and 15 received ketotifen in 1 eye and placebo in the other. Both emedastine and ketotifen significantly inhibited itching (P < 0.05) compared with placebo at all time points after the 5- and 15-minute CAC. Mean raw scores for the active treatments were not statistically different. The mean itching efficacy scores were also not statistically different between active treatments. No adverse events were reported in this study. Conclusion: The results of this study suggest that emedastine and ketotifen are not significantly different with respect to anti-itching efficacy in the CAC model of acute allergic conjunctivitis.