Are individuals taking metformin for type 2 diabetes still allowed one or two alcoholic drinks daily?
—Mario E. Palacios, MD, Woodstown, N.J.

The primary concern for use of metformin is the rare but potentially life-threatening development of lactic acidosis. Most of the contraindications to metformin’s use are thus associated with a higher risk of lactate buildup, such as renal impairment (serum creatinine concentration >1.4 mg/dL in women and >1.5 mg/dL in men), use of IV radiocontrast material with potential for acute alteration in renal function, underlying metabolic acidosis, or conditions such as cardiovascular collapse, sepsis, etc., that could lead to an alteration in renal function. The use of alcohol per se is not listed as a contraindication. Excessive alcohol intake, whether acute or chronic, is to be avoided. Alcohol theoretically could potentiate the effects of metformin on lactate metabolism. Additionally, hepatic impairment, as might be seen with alcohol use, is listed as a precaution given that the liver is essential in the clearance of lactate. It would therefore be appropriate to counsel your patient about consuming alcohol in moderation, one drink per day for the average-size female and one to two drinks per day for the average-size male.
—Christopher Ruser, MD (119-21)