Last update May 11, 2019
Pemetrexed is an analogue of folic acid that behaves as an antifolate and has antineoplastic and immunosuppressive properties by interfering with the synthesis and cellular replication of DNA.
It is used in the treatment of lung cancer and pleural mesothelioma.
Intravenous administration on the first day of each cycle every 3 weeks.
Since the last update we have not found any published data on its excretion in breast milk.
Its pharmacokinetic data (short half-life, pKa acid and moderately high volume of distribution and percentage of protein binding) make transfer to breastmilk in significant amounts unlikely, but during the treatment of cancer it is recommended to temporarily interrupt breastfeeding due to the potentially serious side effects for the infant.
Pharmacokinetics show that after 3 elimination half-lives (T½) 87.5% of the drug is eliminated from the body; after 4 T½ it is 94%, after 5 T½, 96.9%, after 6 T½, 98.4% and after 7 T½ it is 99%. From 7 T½ the plasmatic concentrations of 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 (xxx hours) as a reference, these 5 T½ would correspond to 18 horas. Due to major side effects, it would be advisable to wait 7 T½, which would correspond to 24 horas. Meanwhile, express and discard milk from the breast regularly to maintain production.
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, the production of milk can be maintained by regularly expressing milk from the breast, being able to return to 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 due to 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).
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Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.
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