Low-dose ethanol predisposes elderly posted patients with type 2 diabetes to sulfonylurea-induced low blood glucose

OBJECTIVE - It has previously been demonstrated that the risk of hypoglycem ia is low among otherwise healthy elderly fasted patients with type 2 diabe tes taking oral sulfonylurea medications. Nevertheless, these agents do cau se hypoglycemia in clinical practice, suggesting that accompanying factors must typically be present for hypoglycemia to occur. Ethanol is one putativ e risk factor that has not been evaluated as a mechanism for low blood gluc ose among sulfonylurea users. We hypothesized that low concentrations of et hanol would reduce blood glucose concentrations in elderly type 2 diabetic patients receiving sulfonylureas during a short-term fast. RESEARCH DESIGN AND METHODS - A total of 10 type 2 diabetic patients, aged 68 +/- 3 years and receiving 20 mg glyburide daily, participated in a prosp ective double-blind placebo-controlled in-patient study consisting of two 2 4-h fasts at least 1 week apart. During hours 14 and 15 of the fasting stud ies, subjects received intravenous infusions of either 4.35 mmol . kg(-1) . h(-1) ethanol (equivalent to one or two alcoholic beverages) or saline pla cebo in random order. Ethanol, plasma glucose, insulin, and counterregulato ry hormones were assessed every 30-60 min during the final 10 h of the fast . RESULTS - Blood ethanol levels peaked at 17 +/- 2 mmol/l (the lower legal l imit of intoxication in New Mexico) during the ethanol study. Plasma glucos e concentrations did not differ at baseline (placebo 8.5 +/- 1.8 vs. ethano l 8.7 +/- 1.7 mmol/l; P = 0.50), but nadir plasma glucose was lower after t he ethanol infusion compared with placebo (4.4 +/- 1.2 vs. 5.0 +/- 1.4 mmol /l; P = 0.01), and the absolute decline in plasma glucose was also greater during the ethanol study than the placebo study (4.7 +/- 0.9 vs. 3.6 +/- 1. 2 mmol/l; P = 0.01). Counterregulatory hormone levels were increased during the ethanol study and nonesterified fatty acid concentrations were suppres sed compared wi;h the placebo study. CONCLUSIONS - Low doses of ethanol predispose fasted elderly type 2 diabeti c patients to low blood glucose during a short-ten fast. This may be one of several mechanisms by which sulfonylurea-induced hypoglycemia occurs in el derly patients.