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.