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Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006-.

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Drugs and Lactation Database (LactMed®) [Internet].

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Last Revision: October 31, 2018.

Estimated reading time: 1 minute

CASRN: 25953-19-9

Chemical structure

Drug Levels and Effects

Summary of Use during Lactation

Limited information indicates cefazolin produces low levels in milk that are not expected to cause adverse effects in breastfed infants. Occasionally disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush have been reported with cephalosporins, but these effects have not been adequately evaluated. Cefazolin is acceptable in nursing mothers.

Drug Levels

Maternal Levels. After a single 500 mg dose of cefazolin intramuscularly to 4 women, cefazolin was barely detectable in the mother's milk and not detected in their breastfed infants' serum.[1]

After intramuscular doses of cefazolin 500 mg three times daily in 10 women, the peak concentration of cefazolin in milk was 0.9 mg/L.[2]

Twenty women were given 2 grams of cefazolin intravenously over 10 minutes. Average milk levels were 1.25 mg/L at 2 hours, 1.51 mg/L at 3 hours and 1.16 mg/L at 4 hours after the dose.[3]

After a single dose of 1 gram of cefazolin given intravenously to 15 women who were 1 month postpartum, milk cefazolin levels averaged 0.75 mg/L 2 hours after the dose.[4]

Infant Levels. Relevant published information was not found as of the revision date.

Effects in Breastfed Infants

Relevant published information was not found as of the revision date.

Effects on Lactation and Breastmilk

Relevant published information was not found as of the revision date.

Alternate Drugs to Consider

(Methicillin-resistant Staph. aureus) Doxycycline, Linezolid, Minocycline, Trimethoprim-Sulfamethoxazole, Vancomycin


Fukada M. Studies on chemotherapy during the perinatal period with special reference to such derivatives of cephalosporin C as cefazolin, cephaloridine and cephalothin. Jpn J Antibiot. 1973;26:197-214. [PubMed: 4542543]
von Kobyletzki D, Reither K, Gellen J et al. Pharmakokinetische untersuchungen mit cefazolin in geburtshilfe und gynakologie. Infection. 1974;2 (Suppl 1):60-7.
Yoshioka H, Cho K, Takimoto M et al. Transfer of cefazolin into human milk. J Pediatr. 1979;94:151-2. [PubMed: 758399]
Zhang Y, Zhang Q, Xu Z. [Tissue and body fluid distribution of antibacterial agents in pregnant and lactating women]. Zhonghua Fu Chan Ke Za Zhi. 1997;32:288-92. [PubMed: 9596854]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

  • Breast Feeding
  • Anti-Infective Agents
  • Antibacterial Agents
  • Cephalosporins

Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.

Copyright Notice

Attribution Statement: LactMed is a registered trademark of the U.S. Department of Health and Human Services.

Bookshelf ID: NBK501303PMID: 30000362


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