Emedastine is a potent, high affinity histamine H1-receptor-selective antagonist with Ki of 1.3 ±0.1 nM for H1-receptors while considerably weaker at H2- (Ki = 49,067 ± 11,113 nM) and H3-receptors (Ki = 12,430 ± 1,282 nM).
Emedastine is a high affinity and high potency histamine antagonist with the highest selectivity for the H1-histamine receptor. Emedastine exhibited the highest affinity for H1-receptors (dissociation constant, Ki = 1.3 +/- 0.1 nM), and was considerably weaker at H2- (K1 = 49,067 +/- 11,113 nM) and H3-receptors (Ki = 12,430 +/- 1,282 nM). The H1-selectivity of emedastine was considerably superior to that of pyrilamine (H2:H1, H3:H1 and H2:H3 ratios of 11887, 12709 and 1, respectively). The potency of emedastine (IC50 = 1.44 +/- 0.3 nM) for antagonizing histamine-induced phosphoinositide turnover in human trabecular meshwork cells compared well with its binding affinity at the H1-receptor[1]. Emedastine displays pharmacodynamic properties comparable with cetirizine and therefore qualifies as a safe and alternative compound with H1-receptor antagonist properties[2]. In the Vienna Challenge Chamber model, ketotifen and emedastine both effectively alleviated ocular symptoms of SAC (seasonal allergic conjunctivitis) after single-dose administration[3].
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