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# FDA Nixes Cefazolin as Surrogate Agent for Cephalosporins
- URL: https://www.fdaweb.com/fda-nixes-cefazolin-as-surrogate-agent-for-cephalosporins/
- Published: 2022-10-24T12:00:00.000Z
- Updated: 2026-09-14T18:04:01.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5153034

FDA says it has determined that there are insufficient data at this time to support a proposed cefazolin susceptible minimum inhibitory concentration (MIC) breakpoint of less than or equal to 16 mg/L as a surrogate for determining breakpoints for oral cephalosporins for treating uncomplicated urinary tract infections (uUTI) due to *Enterobacterales*.

In 2020, the U.S. Committee on Antimicrobial Susceptibility Testing (USCAST) and the Clinical and Laboratory Standards Institute (CLSI) each submitted rationale documents to establish cefazolin as a surrogate agent for predicting the activity of orally administered cephalosporins, including cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and locarbacef for treating uUTIs. FDA says the susceptible breakpoint was suggested “because peak urine concentrations following standard dosing of cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and locarbacef are multiple times the proposed breakpoint.”

Under the 21st Century Cures Act, FDA is required to post information about its recognition about such susceptibility test interpretive criteria that are established by standards development organizations. In a [new notice](https://www.fda.gov/drugs/development-resources/rationale-fdas-position-use-cefazolin-breakpoints-surrogate-determining-breakpoints-oral?ref=fdaweb.com) discussing its rationale, the agency says “no clinical studies were provided that evaluated the efficacy of cefazolin or oral cephalosporins in the treatment of uUTI based on the proposed urine-specific breakpoint for *Enterobacterales*. The submitted materials included studies reviewing the microbiologic and clinical outcomes of uUTI when treated with oral cephalosporins without specifying the distribution of MICs of the urinary pathogens nor the association of MICs with the microbiological or clinical outcomes. No decision support logic was provided using urinary drug exposure-antibacterial response relationships nor probability of target attainment analyses in patients with uUTI.”