New Treatments: Alcaftadine vs. Olopatadine

In February of 2011, a study was conducted by researchers Ono and Jane from the Dobbs Ocular Immunology Laboratories of Emory University School of Medicine & Emory Eye Center and published in Drug Design, Development & Therapy. The study focused on the role of conjunctival tight junctions in the allergen-induced inflammatory response. The tight junctions of the conjunctiva epithelium serve as a barrier to prevent the allergen from entering the conjunctiva and eliciting an immune response. If you remember, the epithelium is similar to a liner, keeping unfavorable things out of the conjunctiva. In people with seasonal allergies, they seem to express a lower level of proteins used to create these tight junctions; less tight junctions results in more allergens breaking through. Also, many allergens have enzymes that can be used to force entry into the conjunctiva.

Enzymes are a type of protein with many different functions. The function of the enzyme depends on what type it is; there are thousands of enzyme types that have been identified. In the case of allergens, they contain a type of enzyme that can breakdown the tight junctions in the epithelium, allowing the allergen to pass through. For example, enzymes from pollen and house dust mite feces have been shown to degrade the junctions, making the conjunctiva more permeable to the allergen. If you remember, once the allergen enters the conjunctiva, it binds to the IgE antibody on the mast cells, stimulating the release of histamine and other mediators to elicit the allergic reaction.

In the study, researchers compared the effect medications alcaftadine and olopatadine on the conjunctival tight junctions. Eighty mice were used in the study. They were broken up into five groups, consisting of sixteen mice each. Each of the five groups were subjected to a different portion of the study. Overall, the goal was to determine which medication, alcaftadine or olopatadine, had a greater efficacy.

The results showed alcaftadine to have a greater anti-histamine effect than olopatadine. More importantly, alcaftadine had a protective effect on the tight junction. Alcaftadine seemed to prevent allergen-initiated breakdown of the tight junctions, decreasing the number of allergen molecules that passed through the conjunctiva. Although the actual mechanism of action is unknown,  the ability of a drug to affect the tight junctions opens up a new avenue of research for allergic conjunctivitis therapy. 

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For more information about olopatadine (Patanol) Click Here