Insulin prescription errors rank first among all prescribed drugs. In an effort to remedy this problem, Eli Lilly is developing a prefilled pen for delivering Humulin R U-500 insulin as well as collaborating on the development of a dedicated U-500 syringe.
This news comes from the Institute for Safe Medication Practices, which says that errors involving U-500 are a major cause for insulin’s number-one ranking among misprescribed drugs. The concern is that because U-500 is a much more concentrated form of insulin than the more commonly prescribed U-100, misprescribing it can have serious consequences. The drug is prescribed for patients who have become extremely insulin-resistant and therefore need more concentrated amounts of insulin per dose than patients who use U-100.
The problem with the drug arises in two areas:
1. Unfamiliarity among prescribers with the differences between the two insulins, opening the door to potential prescription mistakes.
2. U-500 has to be administered using a U-100 syringe or a volumetric syringe; however, U-500 is concentrated differently from U-100 and so the U-100 syringe unit markings can be misleading and inappropriate.
The ISMP says that one problem with misprescribing U-500 often lies in prescribers’ computer setups. U-500 and U-100 may be only one line apart on a screen, making it easy for prescribers to click on the wrong choice once they see the line “Humulin R Injection Solution.” This is especially likely if the prescriber’s computer screen does not make other essential information, such as “100 UNITS/ML” or “500 UNITS/ML,” visible in the same line.
Among the steps ISMP recommends prescribers take to avoid confusing the two insulins are:
• List U-500 apart from other insulins, in its own distinct category, so that it is not confused with U-100.
• Place a hard stop after all U-500 prescriptions that forces prescribers and pharmacists to confirm that a patient requires a concentrated strength insulin.
• If prescribers have no patients who require U-500, simply do not list the insulin in their databases to completely avoid the possibility of a prescription error.
While Lilly is working on creating delivery devices that will eliminate much of the problem, it cannot say when the devices might be available. Aside from research and development, the devices will have to gain regulatory approval, a process whose length nobody can predict.