A disturbing bit of news went around endocrine circles recently. A study that looked at insulin concentration in 18 randomly purchased vials from 5 pharmacies supplied by 3 wholesalers found that the mean concentration was not 100 U/mL or even the minimum standard of 95 U/mL but only 40.2 U/mL with a range of 13.9 to 94.2 U/mL. The assumption is that they contained the proper concentration when manufactured but were negatively impacted during storage and transport. All 9 vials of regular insulin had less than 30 U/mL and 6 of the NPH vials had less than 60 U/mL. Bottom line: patients could be getting a lot less insulin than their physicians are prescribing.
While it might seem odd to say, it is almost better that the regular insulin vials, although sorely below the standard, were almost uniform in concentration; presumably, while patients may be underdosing, the underdosing would be consistent and physicians could safely increase the dose based on the patient’s glucose readings.
But the contents of the NPH vials varied so widely (the least concentrated vial had 35 U/mL and the most concentrated had 94.2 U/mL) that a patient could have wildly different glucose readings depending on which vial they got at the pharmacy.
We counsel our patients on maintaining consistency in their food intake, in their daily schedule, and in their physical activity. We don’t expect them to be strictly regimented about things—some flexibility is okay—but they need to be aware that variability in their food intake, the timing of their medications, and their physical activity will lead to fluctuation in blood glucose and in their daily glucose readings. There is significant data that glucose variability has a deleterious effect on patient outcomes.
So we urge patients to do their part to manage their diabetes.
But if we cannot rely on everyone involved in the insulin supply chain (from the manufacturer, to the wholesaler, to the pharmacy, and if a mail order, the delivery service) to maintain an appropriate environment for the stability of insulin concentration, then neither we nor our patients will be sure if problems with glucose control are the result of patient factors or issues with insulin concentration.
Furthermore, it put patients in danger. If a patient is using a less concentrated insulin and develops hyperglycemia and responds by increasing the next insulin dose, the next time he fills a prescription and receives a vial that is more concentrated, the result could be hypoglycemia and potentially a dangerous hypoglycemic event.
I believe that this needs to be investigated further, and if this is a widespread problem, and if it involves the analog insulins as well, then this is a major safety issue.
Original journal article cited by Dr Young:
Carter AW, Heinemann L. Insulin Concentration in Vials Randomly Purchased in Pharmacies in the United States: Considerable Loss in the Cold Supply Chain. J Diabetes Science Technol.
Please see the following for additional information:
Insulin Concentration Concerns: A message from William T. Cefalu, MD, Chief Scientific, Medical and Mission Officer, American Diabetes Association. Posted on January 22, 2018 by American Diabetes Association.
Tucker ME. Insulin Vials and Pens May Not Contain Sufficient Insulin. Medscape. January 15, 2018. Accessed on January 30, 2018.