The effect of a thiazolidinedione drug, troglitazone, on glycemia in patients with type 2 diabetes mellitus poorly controlled with sulfonylurea and metformin. A multicenter, randomized, double-blind, placebo-controlled trial

BACKGROUND

The thiazolidinediones are a new class of antidiabetes medication that enhances the actions of insulin in muscle, liver, and adipose tissue. Data have been lacking on their use in combination with both sulfonylurea and metformin among patients for whom insulin is the usual therapeutic alternative for improved glycemic control.

OBJECTIVE

To determine the effects of troglitazone on hemoglobin A(1c) level in patients treated with maximum tolerated doses of sulfonylurea and metformin who have hemoglobin A(1c) levels of at least 0.085 (8.5%). This trial was completed before troglitazone was taken off the U.S. market.

DESIGN

Randomized, double-blind, placebo-controlled trial, followed by an open-label extension during which all patients received troglitazone.

SETTING

16 outpatient clinics in Canada.

PATIENTS

200 patients (mean age, 59 years) with type 2 diabetes mellitus and hemoglobin A(1c) levels at least 0.085 (8.5%) (mean hemoglobin A(1c) level, 0.097 [9.7%] and mean fasting plasma glucose level, 12.9 mmol/L [233 mg/dL]) while receiving maximum doses of sulfonylurea and metformin.

MEASUREMENTS

Levels of hemoglobin A(1c), fasting plasma glucose, total insulin, triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol.

RESULTS

Troglitazone, 400 mg/d, when added to sulfonylurea and metformin, significantly decreased hemoglobin A(1c) level by 0.014 +/- 0.002 (95% CI, 0.0167 to 0.0109; P < 0.001) (1.4% +/- 0.2% [CI, 1.67% to 1.09%]) and insulin by 19 +/- 4 pmol/L (CI, 30 to 10 pmol/L; P < 0.001). At 6 months, 43% of troglitazone-treated patients achieved hemoglobin A(1c) levels of 0.08 (8%) or lower compared with 6% of placebo recipients. Efficacy was maintained at 12 months.

CONCLUSIONS

The thiazolidinedione troglitazone, at a dosage of 400 mg/d, is effective when used in combination with sulfonylurea and metformin. Thiazolidinediones may therefore offer an effective alternative to insulin for patients treated with sulfonylurea and metformin who do not achieve adequate glycemic control.

Troglitazone monotherapy improves glycemic control in patients with type 2 diabetes mellitus: a randomized, controlled study. The Troglitazone Study Group

To assess the effects of troglitazone monotherapy on glycemic control in patients with type 2 diabetes mellitus, we carried out a 6-month, randomized, double-blind, placebo-controlled study in 24 hospital and outpatient clinics in the United States and Canada. Troglitazone 100, 200, 400, or 600 mg or placebo once daily with breakfast was administered to 402 patients with type 2 diabetes with fasting serum glucose (FSG) > 140 mg/dL, glycosylated hemoglobin (HbA1c) > 6.5%, and fasting C-peptide > or = 1.5 ng/mL. Prior oral hypoglycemic therapy was withdrawn in patients who received it before the study. FSG, HbA1c, C-peptide, and serum insulin were evaluated at baseline and the end of the study. Analysis was performed on two subsets of patients based on prestudy therapy: Patients treated with diet and exercise only before the study (22% of patients), and those who had been receiving sulfonylurea therapy (78% of patients). Patients treated with 400 and 600 mg troglitazone had significant decreases from baseline in mean FSG and HbA1c at month 6 compared with placebo-treated patients (FSG: -51 and -60 mg/dL, respectively; HbA1c: -0.7 and -1.1%, respectively). In the diet-only subset, 600 mg troglitazone therapy resulted in a significant (P < 0.05) reduction in HbA1c (-1.35%) and a significant reduction in FSG (-42 mg/dL) compared with placebo. Patients previously treated with sulfonylurea therapy had significant (P < 0.05) decreases in mean FSG with 200-600 mg troglitazone therapy compared with placebo (-48, -61, and -66 mg/dL, respectively). Significant (P < 0.05) decreases in mean HbA1c occurred with 400 and 600 mg troglitazone therapy at month 6 (-0.8 and -1.2%, respectively) compared with placebo in this same subset. Significant (P < 0.05) decreases in triglycerides and free fatty acids occurred with troglitazone 400 and 600 mg, and increased high-density lipoprotein occurred with 600 mg troglitazone. We conclude that troglitazone monotherapy significantly improves HbA1c and fasting serum glucose, while lowering insulin and C-peptide in patients with type 2 diabetes. Troglitazone 600 mg monotherapy is efficacious for patients who are newly diagnosed and have never received pharmacological intervention for diabetes.

Metabolic effects of troglitazone monotherapy in type 2 diabetes mellitus. A randomized, double-blind, placebo-controlled trial

BACKGROUND

Troglitazone is a new insulin-sensitizing agent used to treat type 2 diabetes mellitus. The mechanism by which troglitazone exerts its effect on systemic glucose metabolism is unknown.

OBJECTIVE

To determine the effects of 6 months of troglitazone monotherapy on glucose metabolism in patients with type 2 diabetes mellitus.

DESIGN

Randomized, double-blind, placebo-controlled trial.

SETTING

Six general clinical research centers at university hospitals.

PATIENTS

93 patients (mean age, 52 years) with type 2 diabetes mellitus (mean fasting plasma glucose level, 11.2 mmol/L) who were being treated with diet alone or who had discontinued oral antidiabetic medication therapy.

INTERVENTION

Patients were randomly assigned to one of five treatment groups (100, 200, 400, or 600 mg of troglitazone daily or placebo) and had metabolic assessment before and after 6 months of treatment.

MEASUREMENTS

Plasma glucose and insulin profiles during a meal tolerance test; basal hepatic glucose production and insulin-stimulated glucose disposal rate during a hyperinsulinemic-euglycemic clamp procedure.

RESULTS

Troglitazone at 400 and 600 mg/d decreased both fasting (P < 0.001) and postprandial (P = 0.016) plasma glucose levels by approximately 20%. All four troglitazone dosages also decreased fasting (P = 0.012) and postprandial (P < 0.001) triglyceride levels; 600 mg of the drug per day decreased fasting free fatty acid levels (P = 0.018). Plasma insulin levels decreased in the 200-, 400-, and 600-mg/d groups (P < 0.001), and C-peptide levels decreased in all five study groups (P < 0.001). Basal hepatic glucose production was suppressed in the 600-mg/d group compared with the placebo group (P = 0.02). Troglitazone at 400 and 600 mg/d increased glucose disposal rate by approximately 45% above pretreatment levels (P = 0.003). Stepwise regression analysis showed that troglitazone therapy was the strongest predictor of a decrease in fasting (P < 0.001) or postprandial (P = 0.01) glucose levels. Fasting C-peptide level was the next strongest predictor (higher C-peptide level equaled greater glucose-lowering effect).

CONCLUSION

Troglitazone monotherapy decreased fasting and postprandial glucose levels in patients with type 2 diabetes, primarily by augmenting insulin-mediated glucose disposal.