Drug Levels and Effects:

Summary of Use during Lactation:

Cefazolin is acceptable to use during breastfeeding. Limited information indicates that maternal doses of cefazolin up to 2 grams produce 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, has been reported with cephalosporins, but these effects have not been adequately evaluated.

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 0.9mg/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.

Possible Effects on Lactation:

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


1. 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. PMID:4542543
2. von Kobyletzki D, Reither K, Gellen J et al. Pharmakokinetische untersuchungen mit cefazolin in geburtshilfe und gynakologie. Infection. 1974;2 (Suppl 1):60-7.
3. Yoshioka H, Cho K, Takimoto M et al. Transfer of cefazolin into human milk. J Pediatr. 1979;94:151-2. PMID:758399
4. 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(5):288-92. PMID:9596854

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Antiinfective Agents

  • Antibacterial Agents

  • Cephalosporins

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

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