[Synthesis and H2-antihistaminic activity of ring methylated metiamide analogues. 4th communication: H2-antihistaminic agents (author's transl)].

In studies on structure-activity relationships of histamine H2-receptor antagonists, the influence of different imidazole ring methylation on the H2-antagonist activity was investigated. 2-Methyl-, 5-methyl-, 2,5-dimethyl- and unsubstituted analogues of metiamide were prepared and tested. While 5-methyl- and unmethylated analogues with a thiourea group proved to be quite active, the 2-methyl- and 2,5-dimethyl-derivatives, as well as those with a urea group, had only low H2-antihistaminic activity.