DESCRIPTION Azelastine hydrochloride ophthalmic solution, 0.05% is a sterile ophthalmic solution containing azelastine hydrochloride, a relatively selective H 1 -receptor antagonist for topical administration to the eyes. Azelastine hydrochloride is a white crystalline powder with a molecular weight of 418.37. Azelastine hydrochloride is sparingly soluble in water, methanol and propylene glycol, and slightly soluble in ethanol, octanol and glycerine. Azelastine hydrochloride is a racemic mixture with a melting point of 225°C. The chemical name for azelastine hydrochloride is (±)-1-(2H)-phthalazinone,4-[(4-chlorophenyl) methyl]-2-(hexahydro-1-methyl-1H-azepin-4-yl)-, monohydrochloride and is represented by the following chemical structure: Empirical chemical structure: C 22 H 24 CIN 3 O•HCl Each mL of azelastine hydrochloride ophthalmic solution, 0.05% contains: Active: 0.5 mg azelastine hydrochloride, equivalent to 0.457 mg of azelastine base; Preservative: 0.25 mg benzalkonium chloride solution (50%) USP-NF; Inactives: disodium edetate dihydrate, hypromellose, sorbitol solution, sodium hydroxide and water for injection. It has a pH of approximately 5 to 6.5 and an osmolality of approximately 271 to 312 mOsmol/L. chemical structure