Olopatadine HCl was developed by Kyowa Hakko Kirin, and it was first approved by the FOOD and Drug Administration (FDA) of the United States on December 18, 1996, and later approved by the Japanese Pharmaceutical and Medical Device Comprehensive Organization (PMDA) on December 22, 2000. It was approved for marketing by the European Medicines Agency (EMA) on 17 May 2002. It is sold in the United States by Alcon with the name Patanol. Olopatadine HCl is an antihistamine (an anticholinergic medicine and mast cell stabilizers), which is suitable for the treatment of allergic conjunctivitis. Patanol is an eye drop containing 0.1% olopatadine. The recommended dose is 1 drop to the affected eye twice a day with an interval of 6-8 hours.