Antibacterial Drug Labeling Error; Excess Drug Prescribed for Complex Infections

The FDA is warning health care professionals about the risk for dosing errors with the antibacterial drug Zerbaxa (ceftolozane and tazobactam) due to confusion about the drug strength displayed on the vial and carton labeling. Zerbaxa’s vial label was initially approved with a strength that reflects each individual active ingredient (e.g. 1 g/0.5 g). The product, however, is dosed based on the sum of these ingredients (e.g. 1.5 g). To prevent future medication errors, the strength on the drug labeling has been revised to reflect the sum of the two active ingredients. Thus, one vial of Zerbaxa will now list the strength as 1.5 grams equivalent to ceftolozane 1 gram and tazobactam 0.5 gram.


Zerbaxa is used to treat complicated infections in the urinary tract, including pyelonephritis, or in combination with the antibacterial drug metronidazole (Flagyl) to treat complicated intra-abdominal infections caused by susceptible bacterial pathogens. Antibacterial drugs work by killing or stopping the growth of bacteria that can cause illness. In order to reduce the development of drug-resistant bacteria and maintain antibacterial effectiveness, Zerbaxa should be used only to treat infections that are proven or strongly suspected to be caused by susceptible bacteria.


The FDA evaluated seven reported cases of medication error that occurred during preparation of the dose in the pharmacy due to confusion with the display of the strength of individual ingredients on Zerbaxa’s vial label and carton labeling. Listing the individual drug strengths led to confusion because it was different from labeling for other beta-lactam/beta-lactamase antibacterial drugs that express strength as the sum of the two active ingredients. In some cases, this led to administration of 50% more drug than was prescribed. No adverse events were reported among these seven cases.


See the FDA Drug Safety Announcement


See also Medical Law Perspectives, May 2013 Report: Drugs, Dosage, and Damage: Physician Liability for Prescribing or Administering Medication