Control of the blood sugar level is the fundamental treatment for diabetes mellitus. However, it is extremely difficult to effectively control the blood sugar level over a long period, during which complications such as neuropathy, retinopathy and nephropathy may develop. Impaired polyol (sorbitol) metabolism is considered to be a cause of neuropathy among these complications of diabetes. Diabetic neuropathy occurs in a relatively early stage. Its incidence increases with the prolongation of the diabetic condition, and the plight of the patients suffering from extensive tissue damage is profound. In this study, assessment was made regarding the effects of the aldose reductase inhibitor epalrestat, which is expected to reverse the pathogenic mechanism of diabetic neuropathy, on symptoms of neuropathy, erythrocyte sorbitol level, and threshold of vibratory sensibility.
[Subjects] The subjects were 7 male and 4 female outpatients who consistently exhibited spontaneous pain, dysesthesia, and autonomic disorders, or showed abnormalities in the erythrocyte sorbitol level and threshold of vibratory sensibility, and were taking 50 mg of epalrestat (1 tablet) before each meal for at least 6 months. The period of investigation was from October 1992 to March 1993.
[Methods] The subjects were explained about the aim of the study and their informed consents were obtained. They were inquired about symptoms while they were waiting for medicine in the Drug Information Management Office. Data concerning the erythrocyte sorbitol level and threshold of vibratory sensibility were obtained from charts.
[Results and Conclusions] 1) Improvement rates by subjective symptom: 75.0% for spontaneous pain; concerning dysesthesia, 57.1% for numbness of hands and feet, 40.0% for coldness of extremities, 33.3% for hot flushes, 75.0% for hypoesthesia, and 50.0% for itching; concerning autonomic disorders, 75.0% for dizziness on standing up, and 33.3% for abnormal perspiration. 2) Effects by the duration of illness: Improvements were greater as the duration of illness was shorter. 3) Erythrocyte sorbitol level: Improvements were generally unremarkable. 4) Threshold of vibratory sensibility: Fair improvements were observed in general. Neuropathy occurs from a relatively early stage of diabetes, and chronic hyperglycemia is considered to be the most important factor. Regulation of the blood sugar level is essential for the treatment, but if it is impossible, the pain and discomfort of patients may be alleviated by epalrestat, and the administration should be started as early as possible since, in this study, the drug was more effective as the duration of illness was shorter.