Is Trastuzumab 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 Trastuzumab. The text below is quoted from that source — it is not our own verdict.
Summary of use during breastfeeding
Trastuzumab milk concentrations were collected in one mother. Concentrations were low, consistent with it being a large protein molecule with a molecular weight of about of 145,531 Da.[1] It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[2] Until more data become available, trastuzumab should be used with caution during breastfeeding, especially while nursing a newborn or preterm infant. The manufacturer recommends that breastfeeding be discontinued during trastuzumab therapy and for 7 months after the last dose.
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. A woman was diagnosed with breast cancer in pregnancy and received five cycles of 75 mg docetaxel during pregnancy. As soon as clinically feasible postpartum, she was given trastuzumab 600 mg intravenously in the first cycle. Fifteen milk samples were collected over 17 days after the first dose except for days 6, 8, and 14 because no milk was produced on those days. Milk trastuzumab concentrations ranged between 12.7 and 977 mcg/L, with the highest concentration found 10 days after the dose.[3] The authors calculated relative infant dosage in a nonstandard way that did not take low oral bioavailability into account, thereby overstating infant exposure, so it is not reported here.
Infant Levels. Relevant published information was not found as of the revision date.
“No published information” means the studies do not exist yet — not that Trastuzumab 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 “Trastuzumab” (LM1017). 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.