AbstractThe safety of tolrestat use in the diabetic patient was demonstrated by data from 14 double‐blind and open‐label studies conducted in 1,300 patients with diabetic neuropathy; the results were supported by data from earlier bioavailability, pharmacokinetic, and clinical pharmacology trials. There was a generally comparable frequency of complaints in the tolrestat dose groups and placebo groups. In a year‐long double‐blind study, the only complaint considered to by “possibly” drug‐related that occurred with a significantly greater incidence in patients treated with tolrestat than in those on placebo was dizziness. Laboratory test values recorded during the trials supported the positive safety findings of tolrestat. A review of blood urea nitrogen and serum creatinine values did not suggest any potential for tolrestat‐induced renal dysfunction. Infrequently, significant elevations in serum hepatic enzyme (aspartate aminotransferase [AST] and alanine aminotransferase [ALT]) levels occurred, accounting for 27 of 42 possibly drug‐related patient withdrawals following tolrestat administration. On review of these cases, it was concluded that tolrestat may cause hepatocellular damage with coincident elevations in AST and ALT in approximately 2% of patients. Importantly, the abnormalities were reversible after discontinuing the drug, commonly within 8–16 weeks. There was no evidence of a hypersensitivity syndrome in any patient in any study. These results support a favorable safety pr