Bioequivalence of two formulations of ketotifen fumarate ophthalmic solution: a single-center, randomized, double-masked conjunctival allergen challenge investigation in allergic conjunctivitis.

BACKGROUND

Ketotifen fumarate ophthalmic solution 0.025% (reference formulation), a topical mast cell stabilizer/antihistamine combination, has been found to be effective and well tolerated in the prevention of ocular itching associated with allergic conjunctivitis (AC). A recently developed formulation of ketotifen fumarate ophthalmic solution 0.025% (test formulation) contains the same active ingredient in the same concentration as the reference formulation, is intended for twice-daily dosing, and may provide a treatment option in patients with AC.

OBJECTIVE

The aim of this study was to determine the clinical bioequivalence of the test and reference formulations using a conjunctival allergen challenge (CAC) model.

METHODS

This prospective, randomized, double-masked, active- and placebo-controlled CAC study was conducted in a clinical setting (ORA Clinical Research and Development, North Andover, Massachusetts). Patients aged <18 years who had AC, a successful allergen challenge during screening and allergen confirmation visits, a history of ocular allergies, and positive skin-test reactivity were enrolled. Patients' eyes were randomized to receive the test or reference formulation or inactive vehicle (1 drop of 1 study medication per eye per visit). The primary efficacy end point was ocular itching, and the secondary end points were ocular redness, chemosis, lid swelling, tearing, and mucous discharge. Efficacy was assessed following challenge at 8 hours and 15 minutes after instillation. The test and reference formulations were considered bioequivalent if the 95% CIs for the differences in mean ocular itching scores between the 2 groups were within the range of 0.40 to 0.40.

RESULTS

There were 108 patients enrolled (61 men, 47 women; mean age, 42 years; 91.7% white). The test and reference formulations both yielded clinically significant results compared with placebo in the prevention of ocular itching at CACs performed 8 hours and 15 minutes after instillation. At the 8-hour posttreatment CAC, the mean ocular itching scores for test formulation-treated eyes were 1.158, 1.265, and 1.305 units lower, respectively, than for eyes at 3, 5, and 7 minutes that were administered placebo. At 15-minute posttreatment CAC, the mean ocular itching scores for reference formulation-treated eyes at 3, 5, and 7 minutes were 1.481, 1.622, and 1.565 units lower, respectively, than for eyes that were administered placebo. With regard to the primary and secondary efficacy variables, no statistically significant differences were observed between test and reference formulations at any post-CAC time point.

CONCLUSIONS

In this population of patients with AC, the test formulation of ketotifen fumarate ophthalmic solution 0.025% met criteria for bioequivalence to the reference formulation, as established by the protocol. The test and reference formulations were well tolerated in the population studied.