What is the mechanism of action of olopatadine in treating allergic conjunctivitis?

• A. Antihistamine and mast cell stabilization.
• B. Beta-adrenergic agonist.
• C. Antibiotic action.
• D. Vasoconstriction.

Answer: (A)

Olopatadine works through a dual action: it is an antihistamine that blocks H1 receptors and it also stabilizes mast cells in the conjunctiva. Allergic conjunctivitis is driven by allergen exposure causing mast cells to release histamine and other mediators, which then bind to H1 receptors and trigger itching, redness, and swelling. By blocking those receptors, olopatadine prevents histamine from producing these symptoms. At the same time, stabilizing mast cells reduces their tendency to degranulate, so less histamine and other inflammatory mediators are released in the first place. This combination provides quick relief of itching and redness and helps control inflammation. The other options don’t fit because a beta-adrenergic agonist mainly causes vasoconstriction rather than addressing histamine-driven itching and swelling, antibiotics target infections rather than allergies, and vasoconstriction alone does not treat the underlying allergic inflammatory process.