Valproic acid-induced Fanconi syndrome in severely disabled, developmentally retarded, and non-ambulatory epileptic children has gradually become more widespread. Although the mechanism is unclear, renal involvement has been suspected. We investigated the effect of antiepileptic drugs and ambulatory state on renal tubular function in epileptic patients. We studied 77 patients who were treated at the Department of Pediatrics and Child Health, Nihon University Itabashi Hospital. The patients were

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... divided into three groups according to antiepileptic drug administration and ambulatory state: severely disabled patients taking mainly valproic acid (9 cases), ambulatory patients taking valproic acid monotherapy (34 patients), and ambulatory patients taking carbamazepine monotherapy (34 patients). Laboratory analysis of renal tubular function showed that β 2-microglobulin levels were increased significantly in severely disabled patients. In addition, α 1-microgulobulin levels were increased significantly in ambulatory patients receiving carbamazepine monotherapy but not valproic acid. These results suggest that carbamazepine affects renal tubular function to a greater extent than valproic acid in ambulatory non-handicapped patients with epilepsy. We propose the importance of monitoring urinary α 1-microgulobulin and β 2microglobulin levels in epileptic children for the early detection of subclinical renal tubular dysfunction.