Effects of combination therapy with glyburide and insulin on serum lipid levels in NIDDM patients with secondary sulfonylurea failure

Abstract

Objective: To compare the long-term effect of combined treatment with insulin and glyburide versus insulin alone on serum lipid levels in non-insulin-dependent diabetic (NIDDM) patients with secondary failure to sulfonylurea therapy.

Research design and methods: The study was a randomized double-blind placebo-controlled parallel trial with a duration of 325 days. The study was conducted at a referral-based endocrinology clinic. Subjects were a sequential sample of 20 patients with NIDDM with failure to respond to glyburide treatment after at least 1 yr of adequate glucose control with this therapy. The patients were randomized to treatment with insulin and glyburide (IG) or insulin and placebo (IP). Insulin was given twice daily to all patients as a mixture of NPH and regular insulins in dosages aiming at optimal glucose control. Glyburide or placebo was taken before breakfast (7 mg) and dinner (3.5 mg).

Results: Mean HbA1c decreased from 11.1% (range 9.8-12.9%) before insulin to 9.1% (range 6.8-11.4%) on day 325 (P less than 0.001) in IG patients and from 10.3% (range 8.4-13.3%) to 9.0% (range 6.3-11.8%) (P less than 0.05) in IP patients. In both groups, there was an increase in high-density lipoprotein cholesterol of approximately 20% lasting throughout the study (P less than 0.01). During the first 83 days of the study, there was a decrease in serum cholesterol (P less than 0.01) and serum triglycerides (P less than 0.05) in both groups. All changes in lipid variables were comparable in magnitude and duration in both treatment with insulin and glyburide in NIDDM patients with secondary sulfonylurea failure improves lipid metabolism to a similar degree as insulin therapy alone.