Letrozole and Breastfeeding

Summary of use during lactation

A minimal amount of information on letrozole excretion into milk indicates that the amounts might be of concern. Because of harm reported in animal studies, the manufacturer recommends that breastfeeding be discontinued during letrozole therapy and for 3 weeks after the last dose.

Drug levels in milk and infant serum

Maternal Levels. An abstract reported that a relative infant dose of 10.2% was found in nursing mother(s) taking letrozole, who provided 8 milk samples over 24 hours, but other details were not supplied.[1] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

Relevant published information was not found as of the revision date.

Effects on lactation and breastmilk

Relevant published information was not found as of the revision date.

References

1. Monfort A, Jutras M, Martin B, et al. New data on the transfer of untested medication into breast milk. Birth Defects Res 2021;113:831.