Lack of influence of histamine antagonists on digitalis cardiotoxicity.

Experiments were carried out in order to study the interaction between cardioactive glycosides and histamine or histamine H1- AND/OR H2-receptor antagonists in anaesthetized cats or guinea pigs. The toxicity of ouabain or digoxin was tested by infusing the glycosides until idioventricular rhythm or death occurred. Histamine increased the toxicity of ouabain, but the histamine H1- and/or H2-receptor antagonists (metiamide and mepyramine)did not influence the toxicity of digitalis. In cats the increase in pulmonary arterial blood pressure caused by digoxin was not affectedby histamine H1- and/or H2-receptor antagonism in spite of the fact that the increase of pulmonary blood pressure caused by histamine could be abolished by H1-receptor antagonists. Our results indicate that histamine is not involved in the toxic effect of cardiac glycosides.