The Food and Drug Administration (FDA) is warning healthcare providers about the risk for dosing errors with Zerbaxa (ceftolozane/tazobactam; Cubist) due to confusion of the strength displayed on the vial and carton labeling. 

The labeling was originally approved with a strength that shows each individual active ingredient (eg, 1g/0.5g). However, Zerbaxa dosing is based on the total of these ingredients (eg, 1.5g). The strength on the labeling has now been updated to show the sum of the two separate ingredients. A vial of Zerbaxa will display the strength as 1.5g equivalent to ceftolozane 1g and tazobactam 0.5g. 

The FDA had analyzed 7 cases of medication error that occurred during preparation in the pharmacy due to confusion with the strengths displayed on the Zerbaxa vial and carton labeling. Some of the cases resulted in the administration of 50% more drug than prescribed. No adverse events were reported among these cases.

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Previously approved beta-lactam/beta-lactamase antibacterial drug products express the strength as the sum of the two active ingredients in the labeling (eg, ampicillin/sulbactam 1.5g or 3g). Confusion arose when the vial label and carton labeling of Zerbaxa expressed the strength to reflect the individual active ingredients.

Zerbaxa is a combination antibiotic approved to treat complicated urinary tract infections, including pyelonephritis, and in combination with metronidazole to treat complicated intra-abdominal infections caused by susceptible bacterial pathogens.

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