EFFECT OF TERFENADINE ON NASAL PROVOCATION

The effect of premedication with terfenadine, an H-1 antagonist, on na sal challenge with antigen, histamine and methacholine was evaluated. A single dose of terfenadine had no effect on the response to a locali zed challenge with methacholine but completely blocked the secretory r esponse to histamine on both the ipsilateral and contralateral sides. These results suggest that terfenadine has no anticholinergic activity and that the direct and reflex secretory response to challenge with h istamine is mediated by the H-1 receptor. A single dose of terfenadine significantly reduced sneezing and nasal secretion after challenge wi th antigen but had no effect on nasal congestion. A double-blind place bo-controlled clinical trial was undertaken to compare the effects of pretreatment with terfenadine for 1 week on the response to sequential nasal challenge with antigen and histamine. Terfenadine significantly reduced the number of sneezes and the levels of kinins, albumin and T AME esterase activity following challenge with antigen. The levels of histamine were also significantly reduced, suggesting inhibition of th e degranulation of mast cells. The number of sneezes and the levels of albumin were also significantly reduced by terfenadine following chal lenge with histamine.