Last update Feb. 25, 2021
Trastuzumab is a recombinant humanised IgG1 monoclonal antibody against the human epidermal growth factor receptor 2 (HER2). Overexpression of HER2 is observed in 20 %-30 % of primary breast cancers (EMA2020).
Indicated for the treatment of certain breast and gastric cancers.
Intravenous administration in regimens of every 1 to 3 weeks up to a year in duration.
We did not find published data regarding the excretion of this substance through breast milk at the time this last update was completed.
It´s very high molecular weight (> 100,000 Da) makes it very unlikely to pass into breast milk in a significant quantity, since molecules of more than 800 - 1,000 Da do not pass into breast milk (Hale, Almas 2016, Anderson 2016).
Null or negligible passage into breast milk of similar monoclonal antibodies, such as adalimumab, belimumab, certolizumab, golimumab, infliximab, ipilimumab, natalizumab, rituximab, tocilizumab and ustekinumab has been confirmed (Bar-Gil 2021, LaHue 2020, Ciplea 2020, Saito 2020, 2019 and 2018, Krysko 2019, Whittam 2019, Klenske 2019, Matro 2018, Anderson 2018, Bragnes 2017, Witzel 2014, Ross 2014, Fritzsche 2012).
Due to its protein nature, it is inactivated in the gastrointestinal tract without being absorbed (practically nil oral bioavailability) and this hinders or prevents its passage into the infant´s plasma from ingested breast milk (Lactmed, Rademaker 2018, Bragnes 2017, Götestam 2016 , Witzel 2014, Butler 2014, Mervic 2014) except for premature infants and during the immediate neonatal period when there might be a greater intestinal permeability (Sammaritano 2020).
No problems have been detected in infants whose mothers received other similar monoclonal antibodies such as belimumab, bevacizumab, infliximab, rituximab, tocilizumab, or ustekinumab (Bar-Gil 2021, LaHue 2020, Saito 2020, 2019 and 2018, Klenske 2019, Mugheddu 2019, Krysko 2019, Matro 2018, Bragnes 2017, Hyrich 2014, Danve 2014).
Expert authors consider that the use of monoclonal antibodies during breastfeeding is safe or very likely to be safe (Whittam 2019, Matro 2018, Anderson 2018 and 2016, Witzel 2014, Pistilli 2013).
Given the strong evidence that exists on the benefits of breastfeeding and the development of babies and the health of their mothers, it might be appropriate to evaluate the risk-benefit of any maternal treatment, including chemotherapy, and counsel individually each mother who wishes to continue breastfeeding (Koren 2013).
We do not have alternatives for Trastuzumab.
Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.
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