Significance of H 1 and H 2 receptors in the human nose: rationale for topical use of combined antihistamine preparations

Abstract

The aim of this experiment was to study the importance of histamine H 1 and H 2 receptors in the human nose. We therefore provoked 25 healthy human subjects with histamine after local pretreatment with the H 1 receptor antagonist, chlorpheniramine maleate, the H 2 receptor antagonist, ranitidine hydrochloride, and a combination of these two antihistamines. The histamine-induced increase in nasal airway resistance was 52% inhibited by combined use of the two antihistamine sprays ( p < 0.05), 22% by chlorpheniramine alone ( p < 0.05), and 29% by ranitidine. The two sprays together were significantly better than the h 1 antagonist alone ( p < 0.05). These results suggest an equal importance of h 1 and H 2 receptors in nasal blood vessels, and an additive effect of H 1 and H 2 antihistamines. Although chlorpheniramine effectively blocked tickling and the reflex-mediated symptoms, sneezing and hypersecretion, ranitidine had no effect, which suggests an H 1 and not an H 2 effect on sensory nerve endings in the airway epithelium.