Inhibitory effects of azelastine on substance P-induced itch-associated response in mice.

The anti-pruritic mechanisms of azelastine were studied in mice. Scratching induced by intradermal histamine was inhibited by azelastine (30 mg/kg) and chlorpheniramine (30 mg/kg). Substance P-induced scratching was dose dependently suppressed by azelastine (3-30 mg/kg), but not by chlorpheniramine (10 and 30 mg/kg). Azelastine (30 mg/kg) inhibited the substance P-induced production of leukotriene B4, but not prostaglandin E2, in the skin. Azelastine (3-30 mg/kg) suppressed scratching induced by intradermal injection of leukotriene B4. The results suggest that inhibition of the production and action of leukotriene B4, as well as an anti-histamine action, is involved in the anti-pruritic action of azelastine.