Tegafur

Tegafur is a prodrug of fluorouracil used in the treatment of neoplasms of the breast, head, neck and gastrointestinal tract.
It is administered orally in 2 daily doses for 3 or 4 weeks followed by a week of rest and intravenously daily for 5 days.

Since the last update we have not found published data on its excretion in breastmilk.

Its pharmacokinetic data (low molecular weight, low protein binding, high liposolubility and high pKa) makes it probable it will transfer into milk in amounts which could be significant.

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 it is 94%, after 5 T½, 96.9%, after 6 T½, 98.4% and after 7 T½, 99%. From 7 T½ the plasma concentrations of the drug in the body are negligible. In general, a period of at least five half-lives can be considered a safe waiting period before breastfeeding again (Anderson 2016).

Taking the longest published T½ of all the active metabolites as a reference, these 5 T½ would correspond to 3 days. Due to major side effects, it would be advisable to wait 7 T½, which would correspond to 4,5 days. Meanwhile, express and discard milk from the breast regularly to maintain production.

Tegafur is sometimes administered with gimeracil and oteracil, two adjuvants whose only function is to prevent the degradation of 5-fluoruracil by blocking the enzyme that metabolizes it and thus increasing its action. With elimination half-lives of 4 and 9 hours respectively, they do not change the waiting time before breastfeeding again when tegafur is administered on its own.

When it is possible to do so, 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.

During the treatment of cancer, breastfeeding should be interrupted temporarily 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, production of milk can be maintained by regularly expressing breastmilk, being able to resume breastfeeding 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). This possibly occurs temporarily with subsequent recovery, although no harmful effects are assumed or have been reported in breastfed infants.

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

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

See below the information of this related product:

• Fluorouracil (Unsafe. Moderate/severe adverse effects. Compatible under certain circumstances. Follow-up recommended. Use safer alternative or discontinue breastfeeding from 5 to 7 T ½ . Read Commentary.)