Emedastine-¹³C-d₃is intended for use as an internal standard for the quantification of emedastine by GC- or LC-MS. Emedastine is a histamine H₁receptor antagonist (K_i= 1.3 nM).¹It is selective for histamine H₁over H₂and H₃receptors (K_is = 49 and 12.43 µM, respectively), as well as α₁-, α₂-, and β₁-adrenergic and dopamine D₁and D₂receptors, and the serotonin (5-HT) receptor subtypes 5-HT₁and 5-HT₂at 10 µM.^1,2Emedastine inhibits histamine-induced phosphoinositide turnover and intracellular calcium mobilization in primary human conjunctival epithelial cells (HCECs; IC₅₀s = 1.6 and 2.9 nM, respectively).³It also inhibits histamine-stimulated secretion of IL-6, IL-8, and GM-CSF by primary HCECs (IC₅₀s = 2.23, 3.42, and 1.50 nM, respectively).⁴Ocular application of emedastine prior to histamine challenge inhibits vascular permeability in guinea pigs.²Formulations containing emedastine have been used in the treatment of allergic conjunctivitis.

1.Sharif, N.A., Su, S.X., and Yanni, J.M.Emedastine: A potent, high affinity histamine H1-receptor-selective antagonist for ocular use: Receptor binding and second messenger studiesJ. Ocul. Pharmacol.10(4)653-664(1994) 2.Yanni, J.M., Stephens, D.J., Parnell, D.W., et al.Preclinical efficacy of emedastine, a potent, selective histamine H1 antagonist for topical ocular useJ. Ocul. Pharmacol.10(4)665-675(1994) 3.Sharif, N.A., Xu, S.X., Magnino, P.E., et al.Human conjunctival epithelial cells express histamine-1 receptors coupled to phosphoinositide turnover and intracellular calcium mobilization: Role in ocular allergic and inflammatory diseasesExp. Eye Res.63(2)169-178(1996) 4.Weimer, L.K., Gamache, D.A., and Yanni, J.M.Histamine-stimulated cytokine secretion from human conjunctival epithelial cells: Inhibition by the histamine H1 antagonist emedastineInt. Arch. Allergy. Immunol.115(4)288-293(1998)