[Synthesis and H2-antihistaminic effect of N,N'-bisheteroaryl N,N'-bisheteroaryl-substituted cyanoguanidines and 2-nitro-1,1-ethenediamines. 17. H2-antihistaminics].

In studies on structure-activity relationships of histamine H2-receptor antagonists, cyanoguanidines and 2-nitro-1,1-ethendiamines, which contain the heterocyclic rings of ranitidine and cimetidine twofold, were prepared and tested for their H2-antihistaminic activity on the isolated guinea-pig atrium and on the histamine stimulated acid secretion of the anaesthetized rat. While the N,N'-disubstituted keten-N,N-acetales 8 and 11 possess markedly stronger H2-antagonistic activity than Ranitidine, the analogously substituted cyanoguanidines 3b and 6 proved to be as effective as the reference substance. The substances 3a and 13, with unsubstituted C-5 position of one heterocyclus, showed lower potency.