Erlotinib Hydrochloride

Inhibitor of Epidermal Growth Factor receptor that acts by inhibition of tyrosine kinase phosphorylation and used to treat certain small cell lung cancers and advanced metastatic pancreatic cancers. Oral administration once daily.

At latest update, relevant published data on excretion into breast milk were not found.

Its pharmacokinetic characteristics (very high plasma protein binding, very large volume of distribution and moderately elevated molecular weight) make it very unlikely its excretion into breast milk in significant amounts.

Its long half-life could facilitate excretion in breast milk and due to its high bioavailability with food (≈ 100%) it would have systemic action in the infant.

The most common adverse effects of erlotinib are rash and diarrhoea. ^(Martindale) 

It is known from pharmacokinetics 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 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 T½ published as a reference (36 hours), these 5 T½ would correspond to 180 hours (8 days). Meanwhile, express and discard milk from the breast regularly. This does not allow breastfeeding during treatment.

Abrupt weaning can be psychologically traumatic for both the mother and the infant. ^{(Pistilli 2013).} 

Until more published data is known about this drug in relation to breastfeeding, better known alternatives may be preferable, especially during the neonatal period and in the event of prematurity.

If used during lactation, it is advisable to monitor growth and appetite and the possible appearance of diarrhea in the infant, as well as monitor hepatic function periodically.

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.)