Effects of short-term insulin therapy upon therapeutic response to glipizide

The effect of glipizide alone and glipizide preceded by a short course of insulin therapy (10 weeks) was studied in 69 patients with non-insulin-dependent diabetes mellitus (NIDDM) in a 10-month study. The patients were obese, had poor glycemic control, and, in all patients, first-generation sulfonylurea therapy had failed. The majority were Mexican-Americans, an ethnic population with a high incidence of NIDDM and insulin resistance. Plasma glucose levels were monitored using the eight-point [Saarstedt] series. In the group receiving glipizide alone, mean fasting plasma glucose levels decreased from 255.9 mg/dl at baseline to 228.7 mg/dl at the end of the study; two-hour postprandial glucose levels decreased from 280.1 to 260.5 mg/dl; glycosylated hemoglobin decreased from 9.1 to 7.4 percent; and post-Sustacal C-peptide levels increased from 0.7 to 1.0 pmol/ml. In the group receiving insulin/glipizide, mean fasting plasma glucose levels decreased from 241.1 mg/dl at baseline to 217.0 mg/dl; two-hour postprandial glucose levels increased from 267.2 to 279.0 mg/dl; glycosylated hemoglobin decreased from 9.1 to 7.5 percent; and post-Sustacal C-peptide levels increased from 0.6 to 1.0 pmol/ml. At the end of 10 weeks, insulin administration was associated with a more rapid decrease in the levels of fasting plasma glucose, two-hour postprandial glucose, and glycosylated hemoglobin, but there was no significant difference between the two therapies by the end of the study. Both regimens had a positive influence on reducing the total cholesterol/high-density lipoprotein ratio. More patients in the group receiving insulin/glipizide withdrew from the study, which may have been due to difficulties associated with insulin administration. In conclusion, there does not appear to be a prolonged effect of insulin treatment on the post-receptor defect. Some patients in whom first-generation oral agents fail may not have to be given permanent insulin therapy, especially those with fasting plasma glucose levels of less than 200 mg/dl. There was no overall difference between these treatments with respect to glycemic control or lipoprotein profiles. In the interests of simplifying both therapy and monitoring, enhancing patient compliance, and achieving cost reductions, therapy with glipizide alone ultimately may be sufficient for cases in which immediate control is unnecessary (for example, patients with asymptomatic hyperglycemia, and in the absence of hyperlipidemia and vascular disease).