ISMP was recently reminded by a concerned veterinarian about a medication error that is fatal to our furry family members, even after just licking their owners! The topical chemotherapeutic agent fluorouracil (CARAC, EFUDEX, FLUOROPLEX, TOLAK), often used to treat skin disorders such as actinic keratosis or basal cell carcinomas, is extremely toxic to dogs and cats. Despite receiving emergency veterinary treatment after coming into contact with fluorouracil, mortality rates within 24 hours are high for dogs and cats. When even small amounts of fluorouracil are ingested, the urea cycle is disrupted, resulting in toxic hyperammonemia. Exposure often happens when a pet licks the owner's skin where the medication was applied or chews the container. Clinical symptoms rapidly develop, causing gastrointestinal, bone marrow, and nervous system abnormalities. Neurologic signs of fluorouracil toxicity include altered mentation, tremors, ataxia, and seizures. There is currently no reversal agent available for pets when fluorouracil is ingested. The treatment options are generally palliative to reduce symptoms (http://www.ismp.org/ext/574).
The product labels on fluorouracil do not alert users about this risk. We have communicated with the U.S. Food and Drug Administration (FDA) and USP with the hope that a path is set to address drug toxicities specific to pets. FDA has posted additional information about the problem at: http://www.ismp.org/ext/600. We have asked major drug information vendors to prominently include this information in patient instructions. We urge providers to bring this topic up at safety committees in the hope that practitioners who prescribe fluorouracil creams and solutions will discuss this risk with their patients and the need for safe storage. We also urge pharmacists and other healthcare providers to reinforce this information while providing medication information to patients. Home care clinicians can play a key role in educating patients about this risk. Remind patients to safely store these and all medications out of sight and reach of children and pets.
Helping Patients Avoid Insulin Pen Mix-ups
A pharmacist heard from two patients who mixed up their insulin pens, leading to administration of the wrong insulin. The first patient, a man with type 2 diabetes, had been using a TRESIBA (insulin degludec) pen, 70 units once daily subcutaneously. Because his blood glucose remained uncontrolled, he was also started on a HUMALOG (insulin lispro) pen, 5 units subcutaneously with the first bite of dinner. He inadvertently took 70 units of HumaLOG instead of Tresiba. He immediately realized the error and called Poison Control (1-800-222-1222). He was advised to check his blood sugar every 15 minutes for 3 to 4 hours. He was also instructed to eat glucose-containing foods and beverages regularly during this time to combat hypoglycemia. He was able to maintain a blood sugar of 90 to 150 mg/dL.
The second patient, also with diabetes, had recently been started on a multidose insulin regimen of HumaLOG, 30 units 3 times a day with meals, and Tresiba, 60 units once daily. He inadvertently injected Tresiba 30 units at mealtime instead of HumaLOG. His blood sugar measurements rose to above 300 mg/dL, and he realized he was taking the wrong insulin with his meals. He had no adverse effects other than hyperglycemia.
We have written about the potential to confuse insulin pens in the past, particularly with impaired vision. In the two cases above, neither patient had visual impairment. However, even though HumaLOG and Tresiba pens are produced by different manufacturers, they are similarly shaped and are a similar shade of blue, although they have different label colors. With both patients, the healthcare provider discussed ways to avoid this type of mistake in the future, including verifying the insulin names and strengths/doses, flagging the pens with "rapid-acting" or "long-acting" stickers, and including the brand name on the stickers. We have also heard of using adhesive tape, a rubber band, or a hair tie wound around the pens to differentiate the insulin types. As insulin does not need to be kept in the refrigerator after opening, the pens can be stored in the specific physical locations where they will be administered, such as the bedroom for long-acting Tresiba, and the kitchen or dining room for rapid-acting HumaLOG.
FentaNYL Patch Duration of Drug Delivery Confused as Patch Strength
Transdermal fentaNYL 75 mcg per hour patches were dispensed for a patient with directions to apply one patch every 48 hours. However, the physician had prescribed fentaNYL patches 50 mcg per hour. The hard copy of the prescription read, "fentaNYL patch 72 hour 50 mcg/hour transdermal, one patch to the skin every 48 hours." The pharmacy staff who entered the prescription into the pharmacy computer system read "fentaNYL patch 72," which led him to mistakenly select a 75 mcg per hour patch instead of a 50 mcg per hour patch. The inclusion of the duration of controlled drug delivery (i.e., 72 hours) in the drug description field contributed to this dispensing error.
To reduce the risk of this type of confusion, the duration of controlled drug delivery (i.e., 72 hours) should not be listed within the product description, which should include the release rate per hour (in this case, 50 mcg/hr. The dosing instructions should communicate the frequency of changing the patch (in this case, every 48 hours). Transdermal fentaNYL patches deliver the labeled amount of drug for 72 hours even if they are ordered to be changed more frequently (i.e., every 48 hours). Official prescribing information mentions that a small proportion of adult patients may not achieve adequate analgesia using a 72-hour dosing interval and may require changing the patch every 48 hours if adequate pain control cannot be achieved using a 72-hour regimen. According to the prescribing information, an increase in the dose should be evaluated before changing the dosing interval in order to maintain patients on a 72-hour regimen.
Confusing Syringe Scale
People might be easily confused when measuring liquid medication doses using the syringe scale printed on Covidien's Monoject 3 mL enteral (ENFit) syringes. The scale is marked as 1/2, 1, 1/2, 2, 1/2, 3 mL (Figure). This can easily be misunderstood, reading the intended 11/2 mL or 21/2 mL as just 1/2 mL. We have let the company know the syringe scale should be revised as it is not safe to use. Syringe scales should never indicate doses using fractions but should indicate the entire volume using decimals (0.5, 1.5, 2.5). You may want to use an alternate syringe brand.