Is Trastuzumab safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Trastuzumab. This is a summary of that source — not our own verdict.
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: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.