[Status of antihistaminics in the therapy of bronchial asthma]

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.