Ketotifen fumarate is a sterile ophthalmic solution that contains ketotifen for topical administration to the eyes. We offer these in proper packaging for long time storage. It is a finely crystalline powder with an empirical formula of c 23 h 23 no 5 s and a molecular weight of 425. 50. chemical specifications: • established name: ketotifen fumarate ophthalmic solution • chemical name: 4-(1-methyl-4-piperidylidene)-4 h -benzo[4,5]cyclohepta[1,2- b ] thiophen-10(9 h )-one hydrogen fumarate each ml contains: • active: 0. 345 mg ketotifen fumarate equivalent to 0. 25 mg ketotifen • inactives: glycerol, sodium hydroxide/hydrochloric acid (to adjust ph) and purified water • preservative: benzalkonium chloride 0. 01%. It has a ph of 4. 4 to 5. 8 and an osmolality of 210-300 mosm/kg.