Abstract: Carboxyalkyl heterocyclic derivatives, pharmaceutically acceptable salts thereof, and therapeutic agents containing said compounds as an effective component are useful pharmaceuticals for the treatment of diabetic complications such as diabetic neuropathy, diabetic cataracts and retinopathy, diabetic nephropathy, diabetic dermopathy, and other diabetic microangiopathy. The compounds of the present invention are represented by the following general formula (A): ##STR1## The compounds of the present invention exhibit excellent inhibitory action towards aldose reductase with a high enzyme selectivity. Accordingly, they are useful as drugs for the therapy and prevention of various types of diabetic complications without substantially inhibiting aldehyde reductase.

Abstract: Parabanic acid derivatives, pharmaceutically acceptable salts thereof, and therapeutic agents containing said compounds as an effective component are useful pharmaceuticals for the treatment of diabetic complications such as diabetic neuropathy, diabetic cataracts and retinopathy, diabetic nephropathy, diabetic dermopathy, and other diabetic microangiopathy. The compounds of the present invention are represented by the following general formula (I): ##STR1## wherein R is hydrogen, lower alkyl or benzyl; X is substituted phenyl, optionally substituted benzothiazolyl, optionally substituted naphthyl, optionally substituted pyridyl, anthraquinonyl, phthalimide, or thienyl; and n is an integer from 1 to 3. The compounds of the present invention exhibit excellent inhibitory action towards aldose reductase with a high enzyme selectivity. Accordingly, they are useful as drugs for the therapy and prevention of various types of diabetic complications without substantially inhibitory aldehyde reductase.