[H2 antagonists and the heart].

The large scale use of drugs that block tissue histamine receptors (H1 and H2) creates the problem of possible side effects due to the inhibition of the physiological role of histamine on certain systems and/or the direct action of histamine receptor blockers. In the case of H2 antagonists the effects on the heart so far reported are few but are considered important since they suggest the presence of physiological mechanisms that are as yet imperfectly understood. The literature on the cardiac effects of cimetidine and ranitidine is reviewed and the extent of the effect of the two drugs is outlined on the basis of an analysis of cases presented, experimental protocols and the various hypotheses put forward. Apart from the speculative interest of the study, a possible predisposition to the cardiac effects of cimetidine and ranitidine is identified in patients with major basal pathologies or in critical conditions. On the basis of the large numbers treated worldwide and the sporadic reports of cardiac effects it is concluded that the drugs are very easily handled even from the viewpoint of cardiac effects.