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
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.
Substance Identification
Substance Name
Letrozole
CAS Registry Number
112809-51-5
Drug Class
Breast Feeding
Lactation
Milk, Human
Antineoplastic Agents
Aromatase Inhibitors
Disclaimer: Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.
