Is Methicillin 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 Methicillin. The text below is quoted from that source — it is not our own verdict.
Summary of use during breastfeeding
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.
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. 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.[1]
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.[2]
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 Methicillin 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 “Methicillin” (LM176). 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.