Olopatadine-d 6 is the deuterium labeled Olopatadine. Olopatadine is an orally active and selective histamine 1 (H1) receptor antagonist and a mast cell stabilizer. Olopatadine prevents immunologically stimulated pro-inflammatory mediator release from human conjunctival mast cells. Olopatadine can be used for researching allergic conjunctivitis.