Effect of mepyramine on the untoward side-effects of impromidine

The value of impromidine, a potent histamine H2-receptor agonist, as an effective acid-secretory stimulant is limited by its tendency to cause cardiovascular side-effects. The possibility that the latter may be mediated not only by H2-receptors in the heart and peripheral blood vessels but also by overflow stimulation of H1-receptors was investigated in a double-blind study using impromidine with or without the H1-antagonist, mepyramine maleate. There was no significant difference between the two groups, suggesting that the side-effects are mediated by H2-receptors in the cardiovascular system alone.