Further studies on the mechanism of human histamine-induced asthma: The effect of an aerosolized H 1 receptor antagonist (diphenhydramine)

Abstract

This study was designed to better define the mechanism of histamine-induced bronchoconstriction in humans by pharmacologic manipulation of the postulated bronchial histamine receptor sites. Histamine challenges were performed on a heterogeneous group of adult asthmatic subjects. The cumulative units of histamine required for induction of a sustained 20% or greater decrease in FEV 1 from baseline were determined. The effect of pretreatment with an aerosolized H 1 receptor antagonist, diphenhydramine hydrochloride, was then studied. Analysis of the data showed that the administration of an H 1 receptor antagonist prior to histamine challenge significantly blocked the bronchial response to histamine (p < 0.005). This effect was considered to be due to specific competitive antagonism at the H 1 receptor site and suggests the presence of H 1 receptors in human bronchial mucosa.