Crossover comparison of maximum dose glyburide and glipizide

Patients with non-insulin-dependent diabetes mellitus (NIDDM) failing to respond to therapy with a maximum dose of glyburide (GB) or glipizide (GZ) are often given a trial of the alternate second-generation sulfonylurea (SGS) before insulin therapy is considered. The efficacy of this therapeutic maneuver has not been thoroughly tested. We studied 26 subjects with fasting serum glucose (FSG) levels greater than 8.3 mmol/L (150 mg/dL) despite maximum doses of either GB (20 mg/day) or GZ (40 mg/day). Group 1 consisted of 16 subjects taking GB (mean FSG = 12.7 mmol/L [228 mg/dL]) and group 2 included 10 subjects taking GZ (mean FSG = 13.0 mmol/L [234 mg/dL]). Subjects continued taking their original SGS for 8 weeks then switched to a maximum dose of the alternate agent for an additional 8 weeks. Values for FSG, hemoglobin A1c, and lipids were recorded before the study and after 8 weeks on each SGS trial. No significant changes were noted for any variable in either group. When maximum dose GB therapy was compared to maximum dose GZ therapy in the combined study group (n = 26), no advantage was noted for either agent. We conclude that metabolic control in NIDDM patients failing to respond to therapy with maximum dose GB or GZ is not improved by switching to the alternate SGS.