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  1. Cohen, Michael R. ScD, MS, RPH

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All bottled up

Incorrectly interpreting the label shown below, a nursing student nearly administered the entire contents of a bottle of Greenstone sublingual nitroglycerin (25 tablets) to a patient with angina.


The label states, "nitroglycerin sublingual tablets, USP, 0.4 mg." Elsewhere the label notes that the bottle contains 25 tablets, but that could easily be overlooked because it's not printed close to the drug name and strength. Because the bottle and tablets are so small, the nursing student thought a single dose must be all 25 tablets; she poured all the tablets into a medicine cup and prepared to administer them to the patient. Fortunately, her preceptor quickly corrected the mistake.


Similar errors and near-misses involving other sublingual nitroglycerin products have been reported to the Institute for Safe Medication Practices (ISMP). In one case, a patient's BP dropped to 80/40, requiring transfer to the ICU.


Unlike most tablet or capsule medications in hospitals, nitroglycerin is dispensed in bottles of 25 tablets rather than in unit-dose packaging because of stability issues. The bottles are often stored on patient-care units and may be the only stock bottle of tablets available on units if a robust unit-dose dispensing system exists. Some nurses who are accustomed to unit-dose packaging may not be expecting more than a single dose in a drug container.


ISMP has asked the FDA to require manufacturers to clarify nitroglycerin labeling by stating "0.4 mg per tablet," or "Each tablet contains 0.4 mg" on the carton and bottle label. A slash mark (0.4 mg/tablet) shouldn't be used because the slash could be misinterpreted. In the meantime, ISMP recommends that hospitals package the original amber glass bottle in a plastic bag or plastic amber vial, and affix a label listing the tablet strength as well as standard dosing information.

Figure. Some practit... - Click to enlarge in new windowFigure. Some practitioners have misinterpreted this label to mean that all 25 tablets in the bottle are required to administer one 0.4 mg dose.

Remember, a prescription that seems to call for more than 3 tablets, vials, or other dosage form is a red flag; call the pharmacy for clarification before proceeding.



Lost in the crowd

Cetylev (acetylcysteine) is an antidote for acetaminophen overdose. Label information printed on blister packs of Cetylev 2.5 g and 500 mg effervescent tablets is so tiny and crowded that the viewer can barely see that the product is available in two different tablet strengths. Each strength is packaged within a bar coded carton in strips of two. To create unit-dose packages, they must be cut apart and a bar code label must be added by the hospital pharmacy to clarify the strength as shown above.


Based on dosing that often requires multiple tablets of each strength to treat acetaminophen overdoses and the fact that this medication is likely to be stocked in the ED, ISMP contacted the FDA and the manufacturer to recommend revised labeling. The manufacturer, Arbor Pharmaceuticals, told ISMP that it didn't intend for the blisters to be separated from the carton. However, this is happening in practice, so the company is in the process of evaluating the implementation of a bar coded blister pack. The company also said it recognizes the similarity between the two strengths and has already begun the process of increasing visual differences between the blister packs with a color change for one strength. The timeline for implementation is late this year.

Figure. Labels on se... - Click to enlarge in new windowFigure. Labels on separated blister packs of Cetylev 2.5 g (left) and 500 mg (right) are difficult to read. The hospital pharmacy added bar coded labels to the packages to identify each strength.