Drug provides superior ocular allergy relief

Olopatadine proved superior for each of the endpoints evaluated in the study. The two agents exhibited similar efficacy with respect to itching at the first time point after allergen challenge, but olopatadine was superior at the two later evaluations. Olopatadine was more effective at all time points with respect to reducing redness and chemosis or conjunctival edema.

"Both drugs are in the same class," he said. "Both are multiaction allergy drugs that have antihistamine activity and some mast cell stabilizing properties, as well. This is better than comparing a combination drug with a drug that is solely an antihistamine or a mast cell stabilizer. The results showed that olopatadine is a superior drug to epinastine."

Originally approved in 1996, olopatadine is indicated for treatment of all signs and symptoms of allergic conjunctivitis, Dr. D'Arienzo and his co-authors note in an article published in Current Medical Research and Opinion. Unlike some of ocular antiallergic drugs that were originally developed for rhinitis, olopatadine was initially developed for ophthalmic use. The agent combines an H₁ selective antihistamine with a human ocular mast cell stabilizer that inhibits the release of histamine and other pro-inflammatory mediators. The agent has demonstrated safety and effectiveness in multiple studies involving twice-daily administration.

Initially approved for treatment of rhinitis, epinastine received approval in the United States in 2003 for treatment of allergic conjunctivitis. Epinastine is indicated for the prevention of itching associated with allergic conjunctivitis. Epinastine combines a direct H₁ receptor antagonist and an inhibitor of histamine release from the mast cell. The anti-itching efficacy of the drug was demonstrated in the CAC model.

According to Dr. D'Arienzo and his co-investigators, the CAC model uses standardized allergen extracts and grading scales to create a precise and reproducible ocular allergic reaction. The model has proven invaluable for the development and selection of antiallergic agents and their optimum concentrations. The model has been used to conduct comparative studies of effects of ophthalmic, nasal, and systemic antiallergic drugs on outcomes that have included efficacy, comfort, and onset and duration of action.

The current study involved 66 patients who had a history of ocular allergies and who responded to CAC on two separate visits. A slit lamp exam was performed to exclude patients who had conjunctival redness or itching in either eye at baseline. The patients were not allowed to use any other topical ocular medications or any systemic medications that could affect the outcome of the study.

CAC was performed bilaterally using an allergen to which the subject tested positive in a skin test. The allergen concentration was increased until a positive reaction was elicited bilaterally. Itching was evaluated by the patients using a standardized scale that ranged from 0 (no itching) to 4 (severe itching). Redness and chemosis were evaluated by the treating physicians using a standardized scale of 0 (none) to 4 (severe).