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Cephalexin use while Breastfeeding

Medically reviewed by Last updated on Aug 2, 2023.

Drugs containing Cephalexin: Keflex, Keftab, Zartan, Biocef, Daxbia, Panixine

Cephalexin Levels and Effects while Breastfeeding

Summary of Use during Lactation

Limited information indicates that maternal cephalexin produces low levels in milk that are usually not expected to cause adverse effects in breastfed infants. Cephalexin is an alternative for the treatment of mastitis.[1,2] 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. A rare case of a severe allergic reaction occurred in an infant previously exposed to intravenous cefazolin whose mother began taking cephalexin while breastfeeding. Cephalexin is acceptable in nursing mothers.

Drug Levels

Maternal Levels. After a single 1 gram oral dose of cephalexin in 6 women who were 2 days postpartum, peak milk levels occurred 4 to 5 hours after the dose and averaged 0.51 mg/L (range 0.24 to 0.85 mg/L).[3]

After a single 500 mg oral dose of cephalexin in 2 women (time postpartum not stated), peak milk levels of 0.7 mg/L occurred 4 hours after the dose.[4]

A woman who was 28 days postpartum had been taking oral cephalexin 500 mg plus probenecid 500 mg 4 times daily for 16 days collected 12 fore-and hindmilk samples over a 16-hour period. Milk cephalexin levels ranged from about 0.4 to 1 mg/L over the milk collection period with little correlation to the times of the doses. The authors calculated that an exclusively breastfed infant would receive 112 mcg/kg daily which is much less than the recommended infant dosage of 25 to 100 mg/kg daily. The infant dosage in milk corresponds to about 0.5% of the maternal weight-adjusted dosage which is higher than in previous reports.[5] The higher milk levels in this patient may have been a result of the concurrent probenecid use.

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

Effects in Breastfed Infants

In a prospective follow-up study, 7 nursing mothers reported taking cephalexin (dosage not specified). Two mothers reported diarrhea in their infants. No rashes or candidiasis were reported among the exposed infants.[6]

A prospective, controlled study asked mothers who called an information service about adverse reactions experience by their breastfed infants. One of 11 cephalexin-exposed infants reportedly developed diarrhea during maternal cephalexin therapy.[7]

A woman received intravenous cephalothin 1 g every 6 hours for 3 days. Her breastfed infant had a green liquid stool, severe diarrhea, discomfort and crying. The mother's drug regimen was then changed to oral cephalexin 500 mg plus oral probenecid 500 mg 4 times daily for another 16 days. The infant continued to have diarrhea during this time. The authors rated the diarrhea as probably related to cephalexin in milk.[5]

A 4-month-old infant was treated with intravenous cefazolin for a urinary tract infection. Nine days after being discharged and cefazolin discontinuation, the infant developed a blistering rash over most of the body that was diagnosed as toxic epidermal necrolysis (TEN). The infant was being breastfed (extent unspecified) by his mother who had begun cephalexin 2 days prior to the onset of symptoms. A lymphocyte transformation test performed 4 weeks after treatment for TEN was completed found sensitization to both cefazolin and cephalexin. The infant's reaction was probably caused by cephalexin in breastmilk after initial sensitization and subsequent cross-reaction to cefazolin.[8]

Effects on Lactation and Breastmilk

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

Alternate Drugs to Consider

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


Amir LH. ABM clinical protocol #4: Mastitis, revised March 2014. Breastfeed Med. 2014;9:239–43. [PMC free article: PMC4048576] [PubMed: 24911394]
Berens PD. Breast pain: Engorgement, nipple pain, and mastitis. Clin Obstet Gynecol. 2015;58:902–14. [PubMed: 26512442]
Kafetzis DA, Siafas CA, Georgakopoulos PA, et al. Passage of cephalosporins and amoxicillin into the breast milk. Acta Paediatr Scand. 1981;70:285–8. [PubMed: 7246123]
Matsuda S. Transfer of antibiotics into maternal milk. Biol Res Pregnancy Perinatol. 1984;5:57–60. [PubMed: 6743732]
Ilett KF, Hackett LP, Ingle B, et al. Transfer of probenecid and cephalexin into breast milk. Ann Pharmacother. 2006;40:986–9. [PubMed: 16551765]
Ito S, Blajchman A, Stephenson M, et al. Prospective follow-up of adverse reactions in breast-fed infants exposed to maternal medication. Am J Obstet Gynecol. 1993;168:1393–9. [PubMed: 8498418]
Benyamini L, Merlob P, Stahl B, et al. The safety of amoxicillin/clavulanic acid and cefuroxime during lactation. Ther Drug Monit. 2005;27:499–502. [PubMed: 16044108]
Chu YN, Lee MS, Yang SC, et al. Toxic epidermal necrolysis in an infant induced by drug intake through breast milk. Dermatologica Sinica. 2019;37:86–9. [CrossRef]

Substance Identification

Substance Name


CAS Registry Number


Drug Class

Breast Feeding


Anti-Infective Agents

Antibacterial Agents


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Further information

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