Olopatadine hydrochloride is an antihistamine (as well as anticholinergic) and mast cell stabilizer, sold as a prescriptioneye drop (0.2% solution, Pataday (or Patanol S in some countries), manufactured by Alcon). It is used to treat itching associated with allergic conjunctivitis (eye allergies). Olopatadine hydrochloride 0.1% is sold as Patanol (or Opatanol in some countries). A nasal spray formulation is sold as Patanase, which was approved by the FDA on April 15, 2008. It is also available as an oral tablet in Japan under the tradename Allelock, manufactured by Kyowa Hakko Kogyo.
It should not be used to treat irritation caused by contact lenses. The usual dose for Patanol is 1 drop in each affected eye 2 times per day, with 6 to 8 hours between doses.