FDA Warns Pharmacists About Antibiotic Dose Confusion

The FDA is warning health care professionals about the risk for dosing errors with ceftolozane and tazobactam (Zerbaxa) due to confusion about the drug strength displayed on its labeling.

Zerbaxa is an antibacterial drug indicated to treat either urinary tract infections alone or complicated intra-abdominal infections in combination with metronidazole.

Zerbaxa’s vial label was initially approved to reflect the strength of each individual active ingredient, though the drug is dosed based on the sum of these ingredients. The FDA said this is confusing for health care professionals because it differs from labeling for other beta-lactam/beta-lactamase antibacterial drugs that displays strength as the sum of the 2 active ingredients.

The FDA evaluated 7 reported cases of medication errors that occurred during Zerbaxa preparation in the pharmacy due to this confusing labeling. This led to administering 50% more drug than prescribed in some cases, though no adverse events were reported in any of them.

To prevent future medication errors, the drug labeling has been revised to reflect the sum of the 2 active ingredients, so 1 vial of Zerbaxa will now list the dosage strength as 1.5 g, equivalent to ceftolozane 1 g and tazobactam 0.5 g.

The FDA is urging health care professionals and patients to report any medication errors or side effects stemming from Zerbaxa to its MedWatch Safety Information and Adverse Event Reporting Program.