Is Dicloxacillin safe while breastfeeding?
Here is what LactMed, the Drugs and Lactation Database published by the U.S. National Institute of Child Health and Human Development (NICHD), reports about Dicloxacillin. The text below is quoted from that source — it is not our own verdict.
Summary of use during breastfeeding
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.
Effects on the breastfed infant
Relevant published information was not found as of the revision date.
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
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.
Alternatives LactMed lists
“No published information” means the studies do not exist yet — not that Dicloxacillin is known to be harmful, and not that it is known to be safe. Your prescriber or pharmacist can weigh your baby's age and whether a better-studied alternative would do the same job. Worth asking before stopping a medicine you need.
Source: Drugs and Lactation Database (LactMed), National Institute of Child Health and Human Development (NICHD), via NCBI Bookshelf, record “Dicloxacillin” (LM90). LactMed on NCBI Bookshelf. LactMed is a registered trademark of the U.S. Department of Health and Human Services.
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.