[Asthma and synthetic antihistaminics]

Anti-histamines are considered weakly effective in the treatment of asthma whether in acute exacerbations or as basic therapy. However, there are numerous arguments which plead in their favour, and not only the recognised role of histamines as an important mediator of the immediate response. Besides, since 1948 when it was shown that the first anti-histamines (classical anti-histamines) possessed undeniable anti-histamine like actions, which showed them to have both broncho-dilator activity and a protective effect on bronchospasm induced by inhalation of histamine or allergens. Unfortunately, this efficacy in asthma is only achieved with high doses which are responsible for troublesome side-effects. This is why with the arrival of new anti-histamines specific for H1 receptors, without anti-cholinergic or sedative effects, one can envisage the day when high dose anti-histamines are evaluated in the treatment of asthma. Pharmacological studies in animals have clearly shown their bronchomotor action. Similarly, the first work carried out in men, confirms the anti-asthmatic potential by showing a protective action in the bronchial response, to isocapnic hyperventilation, to exercise and to allergens. As for anti-H2, their impact on asthmatic broncho-constriction is poorly defined: for some they potentiate, for others they inhibit.