Effects of
histamine on bronchial mucosal permeability, mucus secretion and smooth muscle cells change the airway geometry to bronchoconstriction.
Histamine is also involved in the underlying early and late asthmatic response, chronic
inflammation and increased airway responsiveness. The actions of
histamine enhancing bronchial obstruction arise from its interaction with specific H1-receptors. In contrast to the bronchoconstrictive potency of
histamine, antagonists do not lower bronchial resistance. Therefore they are without any
therapeutic effect in acute asthmatic attacks. However,
histamine H1-antagonists produce significant protection against
bronchospasms which are induced experimentally by a variety of conditions in asthmatic patients. The protective actions of modern
histamine H1-antagonists are caused mainly by the capacity to inhibit synthesis or release of mediators which are implicated in airway
inflammation and hyperresponsiveness. Anti-inflammatory properties and restoration of desensitize beta-
adrenoceptor responsiveness account for the possibility to reduce treatment with
glucocorticoids and other drugs at least in some cases. In summary, modern H1-antagonists are useful in longterm control of moderate forms of primarily allergic
asthma.