Azelastine inhibits IgE-mediated human basophil histamine release

To examine the mechanism potentially contributing to therapeutic efficacy of azelastine in allergic rhinitis and asthma, we studied the effect of azelastine on stimulated histamine release from basophils prepared as a mixed leukocyte suspension from human blood. Azelastine was found to significantly inhibit anti-IgE-stimulated basophil histamine release. Time-course experiments indicated that the inhibitory effect of azelastine was immediate and that preincubation of basophils in azelastine was not necessary. In dose-response experiments with azelastine, 1 to 100 mumol/L, significant inhibition of histamine release was consistently observed in azelastine concentrations greater than or equal to 10 mumol/L. This inhibition was dose dependent (r = 0.96; p less than 0.001) with maximal mean inhibition of 91 +/- 8% at 100 mumol/L of azelastine.