Dicloxacillin Levels and Effects while Breastfeeding
Summary of Use during Lactation
Limited information indicates that dicloxacillin levels in milk are very low and are not expected to cause adverse effects in breastfed infants. It is frequently used to treat mastitis in nursing mothers.[1-3] Occasionally disruption of the infant's gastrointestinal flora, resulting in diarrhea or thrush have been reported with penicillins, but these effects have not been adequately evaluated. Dicloxacillin is acceptable in nursing mothers.
Drug Levels
Maternal Levels. After a single oral dose of 250 mg of dicloxacillin in 2 women, milk samples were assayed using a bioassay. Milk levels ranged from 200 to 300 mcg/L between 2 and 4 hours after the dose. The drug was undetectable (lower limit of assay not stated) in milk at 1 and 6 hours after the dose.[4]
Three nursing mothers with mastitis were prescribed dicloxacillin 500 mg every 6 hours. They collected milk samples at 0, 1, 2, 3, 4, 5, and 6 hours after a dose on or after the fourth day of therapy by pumping both breasts and combining the resultant milk. Measurement with liquid chromatography mass spectrometry found that the average peak milk concentration was 67.6 mcg/L at 4 hours after the dose and the average concentration was 57.7 mcg/L. These values resulted in an average infant dosage of 8 mcg/kg daily, which is 0.03% of the maternal weight-adjusted dosage.[5]
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.
Berth WL, Schauberger CW, Alvarado MA, et al. Telephone-based management of lactation mastitis. J Reprod Med. 2009;54:291–4. [PubMed: 19517693]
2.
Amir LH. ABM clinical protocol #4: Mastitis, revised March 2014. Breastfeed Med. 2014;9:239–43. [PMC free article: PMC4048576] [PubMed: 24911394]
3.
Berens PD. Breast pain: Engorgement, nipple pain, and mastitis. Clin Obstet Gynecol. 2015;58:902–14. [PubMed: 26512442]
4.
Matsuda S. Transfer of antibiotics into maternal milk. Biol Res Pregnancy Perinatol. 1984;5:57–60. [PubMed: 6743732]
5.
Muysson M, Datta P, Rewers-Felkins K, et al. Transfer of dicloxacillin into human milk. Breastfeed Med. 2020;15:715–7. [PubMed: 32678981]
Substance Identification
Substance Name
Dicloxacillin
CAS Registry Number
3116-76-5
Drug Class
Breast Feeding
Lactation
Anti-Infective Agents
Antibacterial Agents
Penicillins
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