The effect of a topical tricyclic antihistamine on the response of the nasal mucosa to challenge with cold, dry air and histamine.

We have previously demonstrated that azatadine, a tricyclic antihistamine, known also to inhibit mediator release from mast cells and basophils in vitro, inhibits the early release of histamine and other mediators after nasal challenge with antigen. In this article, we studied the effect of azatadine on preventing the release of histamine after nasal challenge with cold, dry air (CDA) and its effect on antagonizing nasal challenge with histamine. With histamine challenge, azatadine inhibited symptoms (sneezing, nasal congestion, and rhinorrhea) and the increase in the level of albumin in nasal secretions (p less than 0.01 all). With challenge with CDA, the drug had no effect on either symptoms or histamine and N-tosyl-L-arginine methyl ester-esterase release. Although the patterns of mediator release after CDA and after the early reaction to antigen are similar, the pharmacologic control differs, suggesting different mechanisms of induction of histamine release from mast cells.