Introduction: The objective of this study was to compare the efficacy and safety of olopatadine versus epinastine in healthy Japanese adults with a history of allergic conjunctivitis to Japanese cedar pollen.
Methods: This Phase IV double-blind randomized controlled clinical trial comprised three clinical visits over 30 days. Screening tests were performed to identify subjects with a history of allergic conjunctivitis to Japanese cedar pollen in terms of skin sensitivity and positive bilateral reactions to a conjunctival allergen challenge (CAC) with Japanese cedar pollen at Visit 1, and confirmation by a positive bilateral CAC reaction at Visit 2. At Visit 3, the subjects were randomized to receive one drop of olopatadine HCl ophthalmic solution 0.1% (olopatadine) in the left or right eye (1:1 ratio). All subjects received one drop of epinastine HCl ophthalmic solution 0.05% (epinastine) in the contralateral eye as an active control. Five min later, the subjects underwent bilateral CAC tests with one drop of the allergen solution at the concentration that elicited positive reactions at Visits 1 and 2. Efficacy outcomes included the severity of ocular itching at 5, 7, and 15 min and the severity of conjunctival hyperemia at 7, 15, and 20 min after the CAC test, as graded by the investigator by biomicroscopy.
Results: Fifty people participated in this study (25 per group). Olopatadine significantly reduced ocular itching at 7 and 15 min (both p<0.05) and conjunctival hyperemia at 7 and 20 min (p=0.0010 and p<0.05, respectively) after allergen exposure compared with epinastine. There were no adverse events for either treatment.
Conclusion: The results of this single-dose study suggest that olopatadine is superior to epinastine in terms of suppressing ocular itching and hyperemia induced by Japanese cedar pollen during CAC tests. Further studies are needed to confirm these findings in real-life settings.