In vitro activity: Olopatadine is one of the second-generation histamine H1 receptor antagonists that are treated for allergic disorders. Olopatadine significantly inhibited the ear swelling and the increased production of IL-4, IL-1beta, IL-6, GM-CSF and NGF in the lesioned ear. Olopatadine was highly and rapidly absorbed in healthy human volunteers. The urinary excretion of olopatadine accounted for not less than 58% and the contribution of metabolism was considerably low in the clearance of olopatadine in humans. Olopatadine is one of the few renal clearance drugs in antiallergic drugs. Olopatadine was shown to be useful for the treatment of allergic rhinitis and chronic urticaria in double-blind clinical trials. AL-4943A inhibits histamine release in a concentration-dependent fashion (IC50 = 559 microM) from human conjunctival mast cell preparations in vitro. Passive anaphylaxis in guinea pig conjunctiva was attenuated by AL-4943A applied 30 min prior to intravenous or topical ocular antigen challenge (ED50 values 0.0067% and 0.0170%, w/v, respectively).

Pharmacology. 2005 Dec;75(1):45-52; Jpn J Pharmacol. 2002 Apr;88(4):379-97.