The effects of a new generation of H1 antihistamines (cetirizine and loratadine) on histamine release and the bronchial response to histamine in atopic patients.

The effects of two selective H1 receptor blockers, cetirizine and loratadine, in comparison with placebo, on basophil histamine release and the bronchial response to histamine were assessed. The studies were performed in a group of 18 patients with pollinosis and 22 with atopic asthma. Both tests were performed before and after medication. Histamine release from isolated basophils was evaluated by Shore's method using anti-IgE and pollen antigen as stimulants. The bronchial provocation tests were performed by Ryan's method. The results were expressed as PC20FEV1. It was shown that both drugs significantly inhibited basophil histamine release induced by anti-igE or specific allergen. It was also found that these drugs effectively reduced the bronchial response to histamine challenge. These findings confirm the beneficial clinical effect of a new generation of selective H1 blockers in the treatment of IgE-mediated allergic diseases, and also the possible role of these drugs in the therapy of atopic asthma.