Which chemotherapy drug is known to concentrate in breast milk?

Cyclophosphamide is known to concentrate in breast milk, which is pertinent when considering the safety of breastfeeding during cancer treatment. This medication is an alkylating agent commonly used in various cancers, including breast cancer, and has a significant potential for bioaccumulation in breast milk. The implications of this are critical for nursing mothers undergoing chemotherapy, as it may affect the infant if breastfeeding is continued.

In contrast, other agents like cisplatin and doxorubicin have different pharmacokinetics and are less likely to concentrate significantly in breast milk, thus posing less risk for infants during breastfeeding if the mother is receiving these treatments. Paclitaxel, while also used for breast cancer, does not have the same level of accumulation concerns in breast milk as cyclophosphamide. Understanding the pharmacological properties of these medications is crucial for informing patients about the risks and benefits of treatment during lactation.