It's All in the Name (and Sometimes NDC Number)

DECEMBER 01, 2008
Michael J. Gaunt, PharmD

Dr. Gaunt is a medication safety analyst and the editor of ISMP Medication Safety Alert! Community/Ambulatory Care Edition.

Using Suffixes Where Suffixes Do Not Exist

Drug name suffixes are confusing enough without coining our own. Opana (oxymorphone) 10 mg every 4 to 6 hours for moderate-to-severe pain was prescribed for a patient. On the prescription, the physician included the suffix "IR" (eg, "Opana 10 mg IR") to indicate that the immediate-release product was to be dispensed. Because no actual product is called "Opana IR," the pharmacy interpreted the prescription as "Opana ER" (oxymorphone extended release), which is intended to be administered every 12 hours.

It is unknown if the pharmacist received any computer alerts or drug utilization review warnings regarding the high dose. It seems clear, however, that neither the pharmacy computer system nor the patient's insurance plan forced a hard stop on the filling of the prescription. The patient's insurance approved the prescription, and the pharmacy dispensed 45 tablets of Opana ER labeled with instructions to take 1 tablet every 4 to 6 hours. Once home, the patient looked at the prescription label and medication more closely and identified the mistake; however, the prescription could not be corrected until the next day.

Subscribe to Newsletter
Contact ISMP at 215-947-7797, or send an
e-mail message to .

In another event, a physician assistant wrote a prescription for a patient, which was misread by a pharmacy technician as "Vicodin ES" (hydrocodone 7.5 mg, acetaminophen 750 mg). Upon closer examination, the pharmacist thought that the suffix looked more like "RS." The pharmacist called the prescriber's office and learned that the physician assistant had used "RS" to indicate "regular strength." Vicodin (hydrocodone 5 mg, acetaminophen 500 mg) was subsequently dispensed. Because numerous brand and generic combinations of hydrocodone and acetaminophen products are available, a large potential for confusion exists.

Adding a suffix when a suffix is not part of the name can lead to misinterpretation. To minimize the risk of confusion, avoid using nonexistent suffixes. If you do not recognize a suffix written on a prescription, verify the intended medication with the prescriber. When giving or repeating back verbal orders, practitioners always should use the full words "extended release" or "sustained release," not abbreviations. Involving patients also may help; practitioners should alert patients to possible confusion between the various formulations and suffixes.

Clearly Distinguishing NDCs

Byetta (exenatide) is the first in a class of new antidiabetic drugs called incretin mimetics. The medication is used to improve glucose control in adults with type 2 diabetes. Exenatide enhances glucose-dependent insulin secretion, increases B-cell growth/replication, slows gastric emptying, and may decrease food intake. Byetta is supplied as a sterile solution for subcutaneous injection containing 250 mcg/mL of exenatide in a 5-mcg per dose, 60-dose, 1.2-mL prefilled pen (NDC 66780-210- 07), and in a 10-mcg per dose, 60-dose, 2.4-mL prefilled pen (NDC 66780-210- 08). The 5-mcg pen delivers 0.02 mL per activation, and the 10-mcg pen delivers twice that amount. One problem reported with this pen is related to the products' NDC numbers, which differ only by the last digit. The last 2 digits may not be read by some bar-code scanners used during the dispensing process in some facilities and community pharmacy settings.

Additionally, the manufacturer and product codes in the NDC numbers for both pen injectors are the same. This similarity in NDC numbers increases the risk that manual checks of the NDC number may not catch product mix-ups, as many pharmacists use only the middle 4 digits of the NDC number to verify the product. As a result, the wrong size pen has been dispensed. We have notified the manufacturer to request a distinctly different NDC number for each size pen. When manually verifying these products (and others), ensure the complete NDC number is used.