Safety in Lactation: Alkylating drugs

Sarah Fenner, Specialist MI Pharmacist, Midlands and East Medicines Advice Service (Midlands site) & UK Drugs in Lactation Advisory ServicePublished

Alkylating agents, whether used as monotherapy or in combination with other antineoplastics, are contra-indicated in breastfeeding because of their cytotoxic action on dividing cells and their high toxicity in normal therapeutic use. There is a high risk of bone marrow depression, manifested clinically as neutropenia and agranylocytosis, in the breastfed infant, although this has only been observed with cyclophosphamide.
The risks associated with their use will be additive with other antineoplastic agents with which they are normally used in combination.
In most cases it will not be possible to suggest a suitable alternative. Choice of drug will depend on a number of disease and treatment protocol parameters.
There is no evidence on the length of time after treatment before which breastfeeding can be resumed. Therefore, if use of an alkylating agent is deemed clinically necessary, breastfeeding should be discontinued.