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Not All Insulins and Not All Syringes are U-100

May 30, 2017

Problems associated with the use of U-500 insulin syringes. We received two reports of accidental prescribing of the new BD U-500 insulin syringes for outpatients who were using a U-100 insulin product. In one case, an endocrinology clinic called the hospital pharmacy to ask how to order U-500 syringes. During the conversation, it became apparent that there was some confusion about the use of these syringes. The pharmacist stressed that the patient should not use a U-500 syringe to measure any insulin concentration other than U-500, or the measurement would be incorrect, leading to a 5-fold underdose.

At another organization, some providers have been selecting U-500 insulin syringes in error via electronic prescribing systems. There have been 8 incidents where U-500 syringes were prescribed in error, although pharmacists intervened each time and prevented patients from receiving the wrong syringes.

The computer system at the clinic where this happened listed the “U-500” designation far to the right of the entry, making it easy for both the prescriber and dispensing pharmacist to overlook it: “SYRINGE INSULIN SYRINGE 0.5ML 31G 6MM (U-500) XA854 100/Box….” As a result, pharmacy created a ‘quick order’ for U-500 syringes to minimize the risk of providers inadvertently selecting this item during routine order entry. Moving the “U-500” designation to the left of the insulin syringe entry also helps give it prominence. In addition, caution patients about the risk of a mix-up and dosing errors if multiple family members in the home use insulin and both U-500 and U-100 insulin syringes are available. Another issue with U-500 syringes is they lack a needle guard to protect staff from needlestick injuries. Many hospitals refuse to stock U-500 syringes without the needle guard, so staff are unable to train patients who need to use them. We have received multiple complaints about this issue and have communicated with BD, the U-500 syringe manufacturer.

Unfortunately, BD has not made us aware of any plans to produce syringes with safety needles. Since U-500 syringes and pens have become available, we no longer recommend using a tuberculin (TB) syringe or U-100 syringe due to the risk of patients miscommunicating their dose or measuring it incorrectly. If your hospital does not stock U-500 syringes without a safety needle, consider using the U-500 insulin pen to prevent dosing errors. A third issue with U-500 syringes is that they only measure up to 250 units, even though patients who use U-500 insulin may need more than 250 units per dose. (In fact, U-500 insulin pens only measure up to 300 units.) Although many patients’ doses are below this amount, one hospital ran a report recently and found 31 patients in its system who were on doses greater than 250 units per single dose. They also reported that some patients received as much as 700 units per dose, which required multiple subcutaneous injections.

Unfortunately, this may cause some hospitals to return to using TB syringes or, even worse, U-100 syringes. We have communicated this concern to BD and Lilly (the manufacturer of U-500 insulin). Finally, remind staff involved with obtaining drug histories and performing medication reconciliation to be sure to find out what type of insulin syringe (U-100 or U- 500) U-500 insulin patients are using when they state their dose. Some patients that are still using a U-100 syringe will state their dose in “syringe units,” or one fifth of the actual dose they should be receiving with U-500 insulin. Such an error was reported recently. A pharmacy technician obtaining a drug history was confused by a patient who had been drawing up his U-500 insulin with a U-100 syringe. When an order for U-500 insulin was later entered electronically, a 5-fold under-dose was accidently prescribed.


Lessons Learned

Although in the past people routinely used tuberculin syringes to administer U-500 insulin, BD now has U-500 insulin syringes to accurately administer U-500 insulin. When ordering and using insulin syringes be sure to use the right insulin pen with the right insulin concentration. Double and triple check!

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