Context: Retrospective studies have identified oral sulfonylureas, age, and fasting as major risk factors for hypoglycemia in patients with type 2 diabetes. Sulfonylureas may be withheld from elderly patients out of concern for hypoglycemia.
Objective: To evaluate the hypoglycemic effects of maximum doses of once-daily second-generation sulfonylureas administered to fasting elderly patients.
Design: A prospective, randomized, double-blind clinical trial.
Setting: The University of New Mexico General Clinical Research Center.
Patients: Fifty-two sulfonylurea-treated subjects with type 2 diabetes with a mean (SD) age of 65.1 (5.7) years.
Interventions: Subjects were randomly assigned to glyburide or glipizide gastrointestinal therapeutic system (GITS). Each subject participated in three 23-hour fasting studies after the sequential administration of 1 week of placebo and 1 week of 10 mg and 1 week of 20 mg of the assigned sulfonylurea.
Main outcome measures: Occurrence of hypoglycemia (defined as plasma glucose level <3.33 mmol/L [60 mg/dL]) and hormonal parameters during the final 9 hours of the 23-hour fast in patients who had taken sulfonylureas vs placebo.
Results: No hypoglycemia was observed during 156 fasting studies. Plasma glucose level was decreased (nadir, 4.9 mmol/L [88 mg/dL] for a 20-mg dose of glyburide vs 8.3 mmol/L [150 mg/dL] for placebo; nadir, 5.8 mmol/L [105 mg/dL] for a 20-mg dose of glipizide GITS vs 8.7 mmol/L [157 mg/dL] for placebo), and serum insulin was increased in the sulfonylurea studies compared with placebo (P<.001). Plasma glucose parameters did not differ between the 2 sulfonylureas, but C peptide concentrations were increased in the glyburide group compared with glipizide GITS in the 20-mg study (P=.05). Concentrations of epinephrine were increased in the sulfonylurea studies compared with placebo (P<.001). Epinephrine secretion increased when glucose concentration fell below the mean (SD) level of 9.10 (2.66) mmol/L (164  mg/dL) in the 10-mg study and 8.77 (2.83) mmol/L (158  mg/ dL) in the 20-mg study.
Conclusions: Fasting was well tolerated among these elderly patients with type 2 diabetes treated with sulfonylureas. Older age should not be considered a contraindication to sulfonylurea treatment for diabetes. Stimulation of epinephrine secretion at normal or elevated plasma glucose levels appears to be the primary mechanism of protection against hypoglycemia in this study.