Mitomycin

Mitomycin is a very toxic antibiotic with antineoplastic properties produced by the growth of Streptomyces caespitosus. It is indicated in the treatment of several types of cancer such as bladder, gastric, breast, bronchial, eye or pancreatic. It is administered intravenously alone or in combination in regimens of once with repetitions in variable times between 1 to 8 weeks. Also intravesical and ophthalmic administration.

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

During 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 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)}

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 (78 minutes) as a reference, these 5 T½ would correspond to 6,5 hours. Due to major side effects, it would be advisable to wait 7 T½, which would correspond to 9 hours. Meanwhile, breast milk should be expressed and discarded regularly. 

Some authors advise waiting 24-48 hours to breastfeed again (Hale). The manufacturer's data sheet indicates that after 3 hours of administration, "the serum levels of the drug are usually below the detection limit". ^{(AEMPS 2017)}

There is no absorption after intravesical administration, with undetectable plasma levels. ^{(Teva 2017, AEMPS 2017)}

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.

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)}

See below the information of this related product:

• Maternal Cancer; Maternal Neoplasia (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.)