5,6-Dihydro-11-alkylene-morphanthridin-6-ones, their pharmaceutical compositions and method of use

A 5,6-dihydro-11-alkylene-morphanthridin-6-one of the formula I ##STR9## where R.sup.1 and R.sup.2 are hydrogen, chlorine or methyl and R.sup.3 and R.sup.4 together with nitrogen atom by which they are linked form a piperazine ring in which the carbon atoms are unsubstituted or substituted by one or more alkyl radicals of 1 to 3 carbon atoms and the nitrogen atom is substituted by alkyl of 1 to 3 carbon atoms, hydroxylalkyl of 2 or 3 carbon atoms or phenyl which is itself unsubstituted or substituted by fluorine, chlorine, methoxy or methyl, or is in the form of the N-oxide, and/or its physiologically tolerated acid addition salts.