Description: azelastine, a phthalazine derivative, is an antihistamine and mast cell stabilizer available as a nasal spray for hay fever and as eye drops for allergic conjunctivitis. indication :for the symptomatic treatment of seasonal allergic rhinitis and non-allergic rhinitis, as well as symptomatic relief of ocular itching associated with allergic conjunctivitis.mechanism of action:azelastine competes with histamine for the h1-receptor sites on effector cells and acts as an antagonist by inhibiting the release of histamine and other mediators involved in the allergic response.