This active substance is authorized to be administered even to infants six months of age, which downplays the risk of its administration to nursing mothers.
No references are available on published observations about its use during lactation. Many experts think that there are no reason to avoid using it concurrently with breastfeeding, but always with very justified reasons, given the absence of published experiences on this topic.
Warning of the manufacturer:
Studies in rats have shown that montelukast is excreted in milk. It is not known if montelukast is excreted in human milk.
It may be used in nursing mothers only if clearly needed.