Effect of mequitamium iodide (LG 30435) on airway microvascular leakage in the guinea-pig.

Intravenous administration of mequitamium iodide (LG 30435) prevented the increase of tracheobronchial vascular permeability induced either by antigen challenge or by exogenous histamine in the guinea-pig, while it was ineffective against PAF, serotonin or capsaicin. These findings indicate that mequitamium iodide selectively interferes with the effect of histamine on airway microvascular leakage, mediated by histamine H1 receptors, and is more potent than diphenhydramine, mequitazine or astemizole. Histamine receptor antagonism is likely to be major determinant of the antiallergic activity of the compound, although additional mechanisms may be involved.