Olopatadine-d₃is intended for use as an internal standard for the quantification of olopatadine by GC- or LC-MS. Olopatadine is a histamine H₁receptor antagonist (K_i=41 nM).¹It is 1,059- and 4,177-fold selective for histamine H₁over H₂and H₃receptors, respectively. Olopatadine inhibits histamine-induced phosphoinositide turnover in isolated human conjunctival epithelial cells, isolated human corneal fibroblasts, and human trabecular meshwork (TM3) cells (IC₅₀s = 9.5, 19, and 39.9 nM, respectively).In vivo, olopatadine inhibits passive cutaneous anaphylaxis in rats (ED₅₀= 49 µg/kg) and IgG1-mediated bronchoconstriction in ovalbumin-sensitized guinea pigs (ED₅₀= 30 µg/kg).²Formulations containing olopatadine have been used in the treatment of allergic rhinitis and conjunctivitis, as well as in the treatment of itch in patients with well-controlled urticaria.

1.Sharif, N.A., Xu, S.X., and Yanni, J.M.Olopatadine (AL-4943A): Ligand binding and functional studies on a novel, long acting H1-selective histamine antagonist and anti-allergic agent for use in allergic conjunctivitisJ. Ocul. Pharmacol. Ther.12(4)401-407(1996) 2.Ohshima, E., Otaki, S., Sato, H., et al.Synthesis and antiallergic activity of 11-(aminoalkylidene)-6,11-dihydrodibenz[b,e]oxepin derivativesJ. Med. Chem.35(11)2074-2084(1992)