Attenuation of histamine-induced airway effects by intranasal application of levocetirizine in mice.

The present study was performed to investigate the histamine-induced airway effect of levocetirizine, an active enantiomer of cetirizine, by intranasal application using ddY mice. Nasal rubbing and sneezing after histamine application into the nasal cavity were used as an index of histamine-induced airway effect in mice. Intranasal application of levocetirizine inhibited both nasal rubbing and sneezing concentration-dependently, and the ED50 values were 0.62 (0.51-0.77) and 0.70 (0.51-1.02) %/site for nasal rubbing and sneezing, respectively. ED50 values of cetirizine were 1.24 (1.02-1.59) and 1.35 (1.02-2.08) %/site for nasal rubbing and sneezing, respectively. Levocetirizine also inhibited nasal rubbing and sneezing when administered orally. These results clearly indicate that levocetirizine was about two times more potent than cetirizine by intranasal application, similar to the findings of the former's affinity for human histamine H1 receptors. In addition, the present findings raise the expectation of the development of levocetirizine nasal drops.