December 2016
clinical initiatives, research and current updates in treatment
Insulin Rachel Taylor, Epic Pharmacy Port Macquarie
Insulin is used for treatment of patients with diabetes mellitus type 1 and type 2 when optimal blood glucose control was not achieved with diet, exercise and other medications. In 2014 there were 29,436 people who began using insulin to treat their diabetes in Australia—66% had type 2 diabetes, 23% had gestational diabetes, 9% had type 1 diabetes and 2% had other forms of diabetes.1 Insulin is a high risk medication and incidents causing serious harm have been reported at all stages of the medication management pathway, with 61% of incidents occurring during administration, 17% during prescribing and 10% during dispensing.2 The top three error types were wrong dose, omitted or delayed dose and wrong insulin product. The leading causes of medication errors were incorrect prescriptions, use of dangerous abbreviation IU instead of “units” and incorrect monitoring of blood glucose and dose adjustments. The major contributing factors were “look alike, sound alike” nature of the proprietary names, poor documentation of dose administration on inpatient charts and failure to prescribe the correct insulin preparation.2 Insulin is available in forms that have different pharmacokinetic profiles featuring different time to onset, peak and duration of action. Table 1 (page 4) lists types of insulin and their pharmacokinetic characteristics.
All insulins are provided as 100 units per mL except for the concentrated insulins Toujeo® and Humulin R® U-500. Toujeo® is a concentrated insulin that contains 300 units per mL of long acting insulin glargine. Toujeo® is not interchangeable with Lantus® which contains insulin glargine 100 units per mL.4 Humulin R® U-500 is a short acting concentrated insulin human injection for subcutaneous use in patients with diabetes mellitus requiring more than 200 units of insulin per day. Do not confuse this product with Humulin R® which contains 100 units per mL.5 Concentrated insulins should be discontinued whilst the patient is in hospital and an alternative standard treatment prescribed. However, if the decision is made to continue using concentrated Humulin R® U-500 as inpatient therapy the following risk mitigation strategies are recommended:5,6 ¬¬ Annotate the orders clearly i.e. “Concentrated insulin Humulin
R® U-500” for identification and administration. Place safety alerts on the patient’s charts or notes ¬¬ As a syringe with U-500 scale is not available, to address common dosing confusion when using tuberculin syringe or standard U-100 syringe, the conversion information table5 must be provided to assist with dose selection and indication of required volumes ¬¬ Clearly mark the product and store separately from other insulin preparations ¬¬ Ensure use of uncommon insulin is discussed as part of clinical handover to alert staff of the potential risk ¬¬ Provide clear guidance to the patient on discharge on any decision to change or continue treatment In a hospital setting, consideration should be given to independent double checking before administration of insulin. In addition, steps should be taken to ensure that each insulin pen is used for one patient only3. Extra care should be taken in ensuring that the correct type of insulin and the correct dose is used for each patient to maximise safety and effectiveness of this high risk medication. References available on request.