Heumann Pharma Gmbh & Co.

Geidrun Engler

Helmut Schickaneder

Kurt H Ahrens

Peter Morsdorf

Rolf Herter

Volker Pfanhlert

New benzimidazoles correponding to the general formula I ##STR1## are described, in which the pyridazinone ring is attached in the 5- or 6- position of the benzimidazole ring and R.sup.1 denotes a hydrogen atom or a straight chained or branched C.sub.1 to C.sub.4 alkyl group, R.sup.2 denotes a hydrogen atom, a straight chained or branched C.sub.1 to C.sub.4 alkyl group, a C.sub.1 to C.sub.4 alkoxy group, a hydroxy group, a halogen atom, an amino group or a nitro group, A denotes a hydrogen atom, a group of the formula ##STR2## wherein R.sup.3 denotes a hydrogen atom, an optionally substituted C.sub.1 to C.sub.4 alkyl group or a C.sub.1 to C.sub.4 alkoxy group and B denotes a cyano group, a benzoyl group or a phenylsulphonyl group, or A denotes a group of the formula ##STR3## in which m has the value 2 or 3 and n represents an integer from 1 to 6, and the physiologically acceptable salts thereof as well as processes for their preparation and pharmaceutical preparations. containing these compounds These compounds are new, effective, positive inotropic substances which do not act by the mechanism of phosphodiesterase inhibition.

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Cadolzburg, Germany

Geidrun Engler