Can you take methicillin while breastfeeding?
What LactMed says
The National Library of Medicine’s own summary, quoted in full. We do not write a verdict of our own on this question, and we do not compress theirs into a label.
Amounts of methicillin ingested by the infant in breastmilk are small and would not be expected to cause any adverse effects. 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. Methicillin is acceptable in nursing mothers.
Quoted from Methicillin — Drugs and Lactation Database (LactMed®), National Institute of Child Health and Human Development, revised November 15, 2024.
What LactMed would consider instead
LactMed ends this record by naming the drugs it would consider in place of methicillin. Whether any of them fits depends on what you are treating — this is the database’s list, not a recommendation from us.
- Cefazolin
- Cephalexin
- Dicloxacillin
- Floxacillin
- Oxacillin
- Nafcillin
- Doxycycline
- Linezolid
- Minocycline
- Trimethoprim-Sulfamethoxazole
- Vancomycin
How much methicillin gets into breastmilk
Maternal Levels. Intramuscular injections of methicillin 1 gram every 6 hours for 6 to 9 days in 17 women with monolateral mastitis yielded methicillin levels in milk that reached a peak of 0.31 mg/L at 3 hours after the first dose on the first day in the healthy breast, and much lower levels in the breast with mastitis. After the last dose, peak milk levels of 1.53 mg/L occurred 6 hours after the dose. Methicillin milk levels from both breasts were equal.
After a single intramuscular dose of 1 gram of methicillin in 3 women, milk levels ranged from 0.2 to 0.3 mg/L between 1 and 6 hours.
Infant Levels. Relevant published information was not found as of the revision date.
What has been seen in breastfed infants
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.
Frequently asked questions
Can you take methicillin while breastfeeding?
Amounts of methicillin ingested by the infant in breastmilk are small and would not be expected to cause any adverse effects. The full record is quoted on this page, and the decision is one to make with the person who prescribed it — LactMed itself states it is not a substitute for professional judgement.
What can I take instead of methicillin while breastfeeding?
LactMed lists Cefazolin, Cephalexin, Dicloxacillin, Floxacillin, Oxacillin, Nafcillin, Doxycycline, Linezolid, Minocycline, Trimethoprim-Sulfamethoxazole, Vancomycin as alternate drugs to consider. That is the database's own list for this drug — whether any of them suits you depends on what you are treating.
Does methicillin pass into breastmilk?
LactMed's measured drug levels for methicillin are quoted in full on this page, under "How much gets into breastmilk".
Do I need to pump and dump after taking methicillin?
LactMed does not frame its records that way — it reports measured drug levels in milk and what has been observed in breastfed infants, which is what this page quotes. "Pump and dump" advice for a specific drug and dose should come from your clinician or a pharmacist, not from a general rule.
More on methicillin
LactMed states that the information it presents is not a substitute for professional judgement, and that you should consult your healthcare provider for breastfeeding advice related to your particular situation. Nothing on this page is medical advice.