How long should insulin be used once a vial is started?

Editor’s comment : The commentary by Dr. Grajower has such important clinical relevance that responses were invited from the three pharmaceutical companies that supply insulin in the U.S. and the American Diabetes Association, and all of these combined in this commentary. The commenting letter and individual responses were authored separately and are completely independent of each other. Diabetic patients treated with insulin, whether for type 1 or type 2 diabetes, are prone to often unexplained swings in their blood glucose. These swings can vary from dangerously low to persistently high levels. Most diabetic patients, and most physicians, will adjust insulin regimens so as to avoid hypoglycemia at the expense of hyperglycemia. Among the “textbook” reasons for variable glucose responses to any given insulin regimen are 1 ) site of administration, 2 ) exercise, 3 ) bottles not adequately mixed before drawing the insulin (for NPH, Lente, or Ultralente), and 4 ) duration of treatment with insulin (1). A new insulin was marketed by Aventis Pharmaceuticals about 1 year ago, insulin glargine (Lantus). The manufacturer seemed to stress that patients not use a started bottle of this insulin for >28 days (2). Two patients of mine highlighted this point. L.K. is a 76-year-old woman with type 2 diabetes, diagnosed at 55 years of age, and treated with insulin since age 56. Her insulin regimen was changed to Lantus at night together with Novolog before meals. She monitors her blood glucose four times a day. She used a bottle of Lantus until it ran out; therefore, a bottle lasted for 2 months. Her recent HbA1c was 7.6%. I retrospectively analyzed her home glucose readings by averaging her fasting blood glucose levels for the first 15 days of a new bottle and the last 15 days of that same bottle. The results were 137 ± …