Fluorouracil

Fluorouracil is an analogue of Uracil that acts as an antimetabolite and is used as a treatment for common malignancies, particularly colon and breast cancer administered intravenously every 24 hours or weekly.

It is excreted in breast milk in an undetectable, clinically insignificant amount (Peccatori 2012) that can be explained by its pharmacokinetics: rapid degradation to non-active metabolites and very low liposolubility (Pistilli 2013).

It is known from Pharmacokinetics that after 3 elimination half-lives (T½) 87.5% of the drug is eliminated from the organism; after 4 T½ the 94%, after 5 T½ the 96.9%, after 6 T½ the 98.4% and after 7 T½ the 99%. From 7 T½ the plasmatic concentrations of drug in the organism are negligible. In general, a period of at least five half-lives can be considered a safe waiting period for breastfeeding again (Anderson 2016).

Taking the longest T½ published as a reference, these 5 T½ would correspond to 1.7 hours. Due to the important adverse effects, it would be advisable to wait 7 T½, which would correspond to 2.5 hours. Meanwhile, withdraw and discard milk from the breast regularly.
Some authors recommend waiting 24 hours (89 T½) after the last dose (IV, IM, IP) to restart breastfeeding. (Hale 2017 p388).
When it is possible to do so, the milk detections of each patient to determine the total elimination of the drug would be the best indicator to resume breastfeeding between two cycles of chemotherapy.

The administration of 5-Fluorouracil does not reduce milk production (Pistilli 2013, Peccatori 2012).

In intraocular treatments, doses are minimal and it is unlikely that there is excretion in breast milk (Hale 2017 p388).

During breast cancer treatment, breastfeeding must be interrupted due to potentially serious side effects for the infant. Chemotherapy does not affect milk production during or after treatment. Abrupt weaning can be psychologically traumatic for both the mother and the infant (Pistilli 2013). If the mother wishes, the production of milk can be maintained by regular extraction of the breast, being able to recover lactation in the periods in which no significant traces of the drug remain in the milk (Anderson 2016) or at the end of the treatment (Pistilli 2013).

Some chemotherapeutic agents with an antibiotic effect can alter the composition of the microbiota (bacterial set or bacterial flora) of the milk and the concentration of some of its components (Urbaniak 2014). Possibly, this occurs transiently with subsequent recovery, although no harmful effects are assumed or reported in breastfed infants.

Women undergoing chemotherapy during pregnancy have lower rates of breastfeeding due to difficulties in breastfeeding (Stopenski 2017), needing more support to achieve it.

Given the strength of the existing evidence on the benefits of breastfeeding for the development of babies and the health of mothers, it is convenient to evaluate the risk-benefit of any maternal treatment, including chemotherapy, individually advising each mother who wishes to continue with breastfeeding (Koren 2013).

• Capecitabine (High Risk probable)
• Fluorouracil (Topical use) (Low Risk probable)

Alternatives

We do not have alternatives for Fluorouracil.