From the Editor: The following medication errors took place in a professional
setting. Doctors, pharmacists, and medical staff made them. But, just as when
we make errors ourselves, it is the patient who winds up with the wrong medication.
This time, no one got hurt, but we can't depend on luck. You need to know what
you're taking, how much you're taking, and what each pill is supposed to do.
And, you have both the right and the obligation to question your doctor, nurse,
and pharmacist when something you take gets changed. Ask! You'll be safer.
The following is reprinted from ISMP MEDICATION SAFETY ALERT!, Vol. 9, Number
20, October 7, 2004, published by the Institute for Safe Medication Practices.
Used with permission.
A family practice physician in a community health center prescribed metformin
500 mg bid to a newly diagnosed diabetic man from India, who did not speak English.
When the patient returned to his office a few months later, he brought his medications
with him, as requested. His physician quickly noticed that metformin was missing.
Instead, the patient had a prescription bottle labeled as metronidazole with
directions to take 500 mg twice a day. The prescription had been refilled several
times. Luckily, the patient's diabetes remained stable, and he seemed to suffer
no adverse effects from two months of unnecessary antimicrobial therapy.
The physician notified the pharmacy of the error and asked the pharmacist to
check the original prescription, which had been written clearly and correctly
for metformin. Upon further investigation, the pharmacist found the computer
entry screen for selecting these medications included METF (for metformin) and
METR (for metronidazole).
Apparently, one of the pharmacy staff members had entered MET and selected the
wrong medication that appeared on the screen.
In another community pharmacy, the same mix_up happened twice, one day apart. In one case, metformin was initially dispensed correctly, even though the prescription had been entered incorrectly as metronidazole again, when the wrong mnemonic was chosen. The pharmacist who filled the prescription clearly understood that the physician had prescribed metformin, so he filled the prescription accordingly. However, he failed to notice the order entry error, as he did not compare the prescription vial label to the drug container label.
Unfortunately, the initial order entry error led to subsequent erroneous refills of metronidazole, as stated on the label. In the other case, bulk containers of the medication were available from the same manufacturer, both with similar highly stylized labels. Thus, confirmation bias contributed to staff's selection of the wrong drug. After reading, the staff member believed he had the correct drug.
In a hospital pharmacy, metronidazole 500 mg and metformin 500 mg were accidentally mixed together in the metronidazole storage bin. This resulted in dispensing metformin instead of metronidazole. Fortunately, a nurse recognized the error before giving the patient the wrong medication. Both were generic products, although the brands FLAGYL (metronidazole) and GLUCOPHAGE (metformin) are also available. Unit_dose packages of these drugs contain bar codes, and the printed information is very small, which adds to their similar appearance.
Safe Practice Recommendation:
Metronidazole_metformin mix_ups could be serious, considering the different indications and the potential for drug interactions. To avoid selecting the wrong drug from the screen, consider programming the computer to display the specific brand names along with the generic names whenever the MET stem is used as a mnemonic. To reduce similarity of the containers, purchase these medications from different manufacturers. Another option in hospital settings is to stock only the 250 mg tablets of metronidazole, since metformin is not available in that strength. This option allows a small risk for nurses who may administer just 250 mg when 500 mg is prescribed, but the potential for harm from giving the wrong drug is greater. It's also a good idea to separate the storage of these products.
During the dispensing process, drug names listed on written prescriptions and hospital orders should be matched to computer labels and manufacturers' products. Since metformin is used to treat a chronic condition, and metronidazole is more likely to be used for an acute condition, outpatient refills for metronidazole are less common and, therefore, bear a second look.
Asking physicians to include the drug's indication on the prescription can
also help prevent errors. We'll ask FDA to add these drugs to the list of non-proprietary
names that would benefit from using tall man letters. Meanwhile, underline or
highlight the unique letter characters in these drug names to make their differences
stand out.