The influence of sulfonylurea drugs in enhancing the effect of endogenous
insulin is well documented. Furthermore, combination
therapy with sulfonylurea and
insulin is effective in the treatment of type II
diabetes mellitus. Therefore, to assess the efficacy of this type of combination
therapy in type I diabetes, we conducted a double-blind clinical trial with
tolazamide and
insulin in 15 subjects with type I diabetes. The diagnosis of type I diabetes was confirmed by previous episodes of
diabetic ketoacidosis and undetectable
C-peptide levels in serum samples from blood drawn from patients two hours after breakfast. During the study protocol, placebo or
tolazamide was randomly added to
insulin and the combination
therapy was continued for three months. In the placebo group, levels of fasting plasma
glucose (FPG) and
hemoglobin A1c (HbA1c) did not alter significantly at the end of the study period. However, in the
tolazamide group, levels of FPG and HbA1c markedly improved after administration of
tolazamide (FPG levels before
therapy, 10.8 +/- 0.9 mmol/L [mean +/- SEM]; after
therapy, 6.7 +/- 0.4 mmol/L; HbA1c levels before
therapy, 10.9% +/- 0.6%; after
therapy, 9.6% +/- 0.5%). Therefore, adjuvant
therapy with
tolazamide and
insulin may be beneficial in achieving adequate metabolic control in type I
diabetes mellitus.