Azelastine competes with histamine for the H1-receptor sites on effector cells and acts as an antagonist by inhibiting the release of histamine and other mediators involved in the allergic response.
Azelastine is a relatively selective histamine H1 antagonist, which inhibits the release of histamine and other mediators from cells (e.g. mast cells) involved in the allergic response. It has some affinity to H2 receptors. Based on in vitro studies using human cell lines, inhibition of other mediators involved in allergic reactions (e.g. leukotrienes and PAF) has been demonstrated with azelastine. Azelastine may also inhibit the accumulation and degranulation of eosinophils at the site of allergic inflammation.
Azelastine hydrochloride is oxidatively metabolized to the principal metabolite, N-desmethylazelastine, by the cytochrome P450 enzyme system, however the exact cytochrome P450 isoenzyme involved has not been determined. The major metabolite, desmethylazelastine, also has H1-receptor antagonist activity.