Effect of azelastine hydrochloride on vascular permeability in hypersensitivity reaction skin site in guinea pig.

4-(p-Chlorobenzyl)-2-(hexahydro-1-methyl-1H-azepine-4-yl)-1-(2H)-phthalazinone hydrochloride(azelastine) is a new compound promising anti-allergic effect, which was tested on increased vascular permeability in two types of hypersensitivity skin reaction in guinea pigs. The reversed passive Arthur (RPA) reaction was induced by bovine serum albumin and its heterologous or homologous antibody IgG. A monophasic permeability response, shown by amount of extravasated Evan's blue, was considerably suppressed by pretreating the animals orally with azelastine at different concentrations. In contrast, antihistamines such as triprolidine, chlorpheniramine and pyrilamine had no effect on the vascular response. Thus the potent antiexudative action of azelastine was demonstrated for the RPA reactions in guinea pigs as the model. However, the vascular response in tuberculin reaction in guinea pigs was not influenced by azelastine suggesting a different permeability mechanism.