Response to Letter to the Editor

Abstract

The letter to the editor presents some valuable additional information on the use of U-500 insulin. As described in our review, directions regarding the use of U-500 insulin should include units and volume, regardless of the syringe being used. As the letter indicates, regular U-100 syringes can be used safely in patients administering U-500 insulin, with adequate education by a certified diabetes educator, pharmacist, or other specialized health care professional. As stated in the letter and our review, the patient must be able to describe the insulin dose in units and in volume for the syringe of use. While U-100 insulin syringes can be used safely for the administration of U-500 insulin, there still may be some confusion among patients. Tuberculin or volumetric syringes can still be used as an option for the administration of U-500 insulin, especially in situations where insurance payment is not a problem, such as managed care systems and the federal government. The letter discusses additional information about the pharmacokinetics and pharmacodynamics of U-500 insulin. To provide further clarification, U-500 insulin allows for a decreased volume of administration and fewer injections, which may ultimately lead to better glycemic control and patient satisfaction. There are no randomized controlled trials comparing U-500 insulin with other types of insulin. A majority of the available evidence is based on opinions and retrospective data from clinical settings. Based on the pharmacokinetic data, U-500 insulin has an extended prandial action with basal activity, allowing it to be administered prior to meals. The letter brings up additional literature to support the use of U-500 insulin in a hospital setting. The article published by Samaan et al provides additional guidelines for the use of U-500 insulin in an institutional setting. All institutions should have a policy with U-500 insulin. Emphasis on the word ‘‘concentrated’’ should be highlighted in the policies as described by Institute for Safe Medication Practices (ISMP). There are other important components of institutional policies regarding U-500 insulin that should be noted, including monitoring of glucose levels and protocols for hyperglycemia and hypoglycemia. The tool developed by Samaan et al utilizes a unit-per-unit conversion technique. It should be noted that other publications on U-500 insulin provide other information for the initial conversion. From selected publications, examples of conversions include unit-per-unit, 20% dose reduction in insulin to prevent hypoglycemia, and 20% dose increase in insulin in uncontrolled hyperglycemia. The letter case study follows a unit-per-unit conversion and accounts for the concentration of U-500 insulin by dividing by 5. This produces the same result as our review without rounding. The letter provides an example of appropriate directions when using a U-100 insulin syringe. We appreciate the feedback and additional insight from the readers of the Journal of Pharmacy Practice.