Copper chelator used in the treatment of Wilson's disease. It is excreted in breast milk in clinically insignificant amounts (undetectable levels: Izumi 2012). Copper and zinc levels in breastmilk of mothers treated with penicillamine, trientine or zinc are normal (Izumi 2012). Oral bioavailability, which is very low during periods of fasting, is practically non-existent in the presence of food, especially milk, so it would be very difficult to pass into the infant plasma from the ingested breast milk (PDR 2016).