In vitro actions of ranitidine, a new histamine H2-receptor antagonist.

Ranitidine has been tested on isolated guinea-pig right atrium and rat uterine horn, tissues known to possess histamine H2-receptors; and on isolated guinea-pig ileum a tissue containing histamine H1-receptors. These experiments have shown ranitidine to be a potent competitive antagonist of histamine at H2-receptor sites in vitro. This action is selective since high concentrations of ranitidine do not affect beta-adrenoceptor, histamine H1-receptor and muscarinic receptor mediated responses.