Background: Compared with other insulin regimens, combination therapy with oral hypoglycemic agents and bedtime insulin produces similar improvement in glycemic control but induces less weight gain.
Objective: To determine whether bedtime insulin regimens differ with respect to their effects on weight gain in patients with type 2 diabetes.
Design: Randomized, controlled trial.
Setting: Four outpatient clinics at central hospitals.
Patients: 96 patients (mean age, 58 +/- 1 years; mean body mass index, 29 +/- 1 kg/m2) whose type 2 diabetes was poorly controlled with sulfonylurea therapy (mean glycosylated hemoglobin value, 9.9% +/- 0.2%; mean fasting plasma glucose level, 11.9 +/- 0.3 mmol/L [214 +/- 5 mg/dL]).
Intervention: Random assignment to 1 year of treatment with bedtime intermediate-acting insulin plus glyburide (10.5 mg) and placebo, metformin (2 g) and placebo, glyburide and metformin, or a second injection of intermediate-acting insulin in the morning. Patients were taught to adjust the bedtime insulin dose on the basis of fasting glucose measurements.
Measurements: Body weight, biochemical and symptomatic hypoglycemias, and indices of glycemic control.
Results: At 1 year, body weight remained unchanged in patients receiving bedtime insulin plus metformin (mean change, 0.9 +/- 1.2 kg; P < 0.001 compared with all other groups) but increased by 3.9 +/- 0.7 kg, 3.6 +/- 1.2 kg, and 4.6 +/- 1.0 kg in patients receiving bedtime insulin plus glyburide, those receiving bedtime insulin plus both oral drugs, and those receiving bedtime and morning insulin, respectively. The greatest decrease in the glycosylated hemoglobin value was observed in the bedtime insulin and metformin group (from 9.7% +/- 0.4% to 7.2% +/- 0.2% [difference, -2.5 +/- 0.4 percentage points] at 1 year; P < 0.001 compared with 0 months and P < 0.05 compared with other groups). This group also had significantly fewer symptomatic and biochemical cases of hypoglycemia (P < 0.05) than the other groups.
Conclusions: Combination therapy with bedtime insulin plus metformin prevents weight gain. This regimen also seems superior to other bedtime insulin regimens with respect to improvement in glycemic control and frequency of hypoglycemia.