Abstract: AIM: To study the antiallerergic effects of norastemizole.METHODS: Antiallergic effects of norastemizole were study using rats and guinea pigs.RESULTS: Norastemizole (10^-9-10^-8 mol·L^-1) caused inhibition effect on the hisitamine-induced contraction of isolated guinea pig ileum.Its IC50 was 4.42 ×10^-9mol·L^-1.Norastemizole at oral doses of 0.1, 0.5,1 mg·kg^-1, norastemizole caused a significant inhibition on the histamin-phosphate induced shock in guinea pigs (P<0.01).At doses of 0.5, 1.0 and 2.0 mg·kg^-1, it significantly inhibited homologous PCA (P<0.01).At oral doses of 0.05, 0.5 and 1.0 mg·kg^-1, norastemizole caused a significant inhibition on the increase of skin vascular permeability induced by histamine.CONCLUSION: Norastemizole is a third-generation antihistamine drug, and shows significant advantages over the parent compound astemizole in potency.

Key words: norastemizol, antiallergic, histame-phosphate, isolated guinea pig ileum, permeability