New ranitidine analogues containing the 2-aminobenzimidazole moiety: in vivo and in vitro histamine H2-receptor blocking activity.

The paper reports the pharmacological profile of a new series of ranitidine analogues in which the diaminonitroethene group is replaced by the 2-amino-5(6)-substituted and unsubstituted benzimidazole moieties. These derivatives show a histamine H2-receptor blocking activity comparable to that of the model both in vitro (KB on atria 0.16-1.15 microM) and in vivo (ID50 on the perfused stomach of the anaesthetized rat from 0.34 to 4.10 mumol kg-1 i.v.). The results are consistent with the hypothesis that, at least in the ranitidine analogues, the "urea equivalent" moiety may be replaced by a polar group partially ionized at physiological pH without loss of H2-blocking activity.