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

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Misleading label could lead to overdose

Nucala (mepolizumab) is an interleukin-5 antagonist monoclonal antibody used as an add-on maintenance treatment for patients 12 years and older with severe eosinophilic asthma and for adults with eosinophilic granulomatosis with polyangiitis (EGPA). The recommended dosage for treating asthma is 100 mg administered once every 4 weeks by subcutaneous injection into the upper arm, thigh, or abdomen.


Some healthcare practitioners have been confused by the vial label, which states "100 mg/vial" (see photo below). Healthcare professionals generally expect that the amount of drug listed on the label is the amount contained in the vial. However, each vial of Nucala contains approximately 144 mg of the drug, which includes overfill to facilitate dose preparation. Confusion could lead to an overdose of the medication if the entire amount in the vial is drawn into a syringe by a practitioner who intends to administer a 100 mg dose.


The Nucala preparation instructions state that each vial of mepolizumab 100 mg should be reconstituted with 1.2 mL of Sterile Water for Injection, resulting in a final concentration of 100 mg/mL. The recommended 100 mg dose would then be drawn up as 1 mL, with the overfill remaining in the vial. If practitioners believe the vial holds just 100 mg, as the vial label seems to state, they might withdraw the full volume (that is, 1 mL plus overfill).

Figure. Nucalas labe... - Click to enlarge in new windowFigure. Nucala's label states "100 mg/vial," even though each vial contains 144 mg of the drug.

The drug is supplied only in 100 mg vials so the risk of overdose increases as the dose increases when multiple vials must be used to prepare a prescribed dose. For example, doses as high as 300 mg (given as 3 separate 100 mg injections every 4 weeks) are prescribed for some patients with EGPA. To prepare a 300 mg dose, a practitioner might incorrectly attempt to withdraw the full contents of 3 vials. Because each vial contains 144 mg of the drug, this would amount to a 432 mg dose.


Clinicians should refer users to the package insert for preparation and dosing instructions. Pharmacies should ensure that sterile preparation compounding instructions clearly state that only 1 mL (100 mg) should be withdrawn from the reconstituted vial to ensure the proper dose.



More than 3? Ask for clarification

Safety experts remind all practitioners that when preparing or administering any medication, "If you need more than 3 (pills, vials, or other dosage form), call the pharmacy." A recently reported incident illustrates why.


During orientation, an inexperienced nurse administered an entire bottle of nitroglycerin tablets to a patient (see photo above). The error was witnessed by another nurse, who immediately removed the tablets from under the patient's tongue and the patient wasn't harmed.


This event was likely an unintended consequence of the 50-year-old "unit dose" safety initiative, which was intended to reduce medication errors by dispensing drugs in unit dose packages holding a single dose for patient administration. When a nurse consistently receives medications in unit doses, he or she may assume that every small vial or bottle of medication that is dispensed contains a single patient dose.


ISMP cautions pharmacists to avoid placing multiple doses in one container, but sometimes that's not possible. Nitroglycerin tablets are one example. Because of stability issues, nitroglycerin tablets must be dispensed in their original 25-count amber glass bottle and can't be unit dosed. In addition, for charging purposes, order entry systems require a dispense quantity of 25 tablets, even though the dose is just one tablet at a time. Consequently, scanning the label doesn't trigger an alert that the quantity in the bottle doesn't match the amount to be administered.

Figure. An entire bo... - Click to enlarge in new windowFigure. An entire bottle of 25 nitroglycerin tablets was given to a patient.

Technology is no substitute for safe medication administration practices. To reduce the risk of similar errors, facilities should ensure the medication administration record and automated dispensing cabinet screens include instructions to administer just 1 nitroglycerin tablet sublingually (with additional doses as prescribed) and consider placing a flag label on the glass bottle with this same information. Packaging the nitroglycerin vial in a plastic bag or plastic amber vial, and affixing a label listing the per tablet strength and notation to administer just 1 tablet per dose is another option.