[Guanidinothiazoles with H2-antihistaminic activity. 12: H2-antihistamines]

In studies on H2-antihistaminics, guanidinothiazoles were prepared and tested for their H2-antihistaminic activity on the isolated guinea-pig atrium. Whereas the N,N'-disubstituted cyanoguanidines 3 and 5 possess stronger H2-activity than tiotidine, the 5-substituted 4-pyrimidinones 7a, b proved to be as effective as the reference substance.