Carbostyril compounds

A carbostyril compound represented by the formula (I):

• ##STR59## wherein R.sub.1 represents a hydrogen atom or a straight or branched chain alkyl group having 1 to 6 carbon atoms, R.sub.2 represents a hydrogen atom, a straight or branched chain alkyl group having 1 to 6 carbon atoms or a phenylalkyl group selected from the group consisting of monophenylalkyl and diphenylalkyl groups having a straight or branched chain alkyl group having 1 to 6 carbon atoms in the alkyl moiety, R.sub.3 represents a hydrogen atom and R.sub.4 represents a phenylalkyl group selected from the group consisting of monophenylalkyl and diphenylalkyl groups having a straight or branched chain alkyl group having 1 to 6 carbon atoms in the alkyl moiety thereof or a phenoxyalkyl group having a straight or branched alkylene group of 1 to 6 carbon atoms in the alkyl moiety thereof, the 3,4-bond of the carbostyril nucleus represents a single or double bond, said phenylalkyl or phenoxyalkyl being unsubstituted or having 1 to 3 substituents being selected from the group consisting of alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms, halogen atoms, alkylene dioxy groups having 1 to 2 carbon atoms, a carbamoyl group and a substituted or unsubstituted phenyl group, and the pharmaceutically acceptable acid addition salts thereof.