Is Methotrexate safe while breastfeeding?
Here is what NIH LactMed, the U.S. National Library of Medicine's authority on medicines and breastfeeding, reports about Methotrexate. This is a summary of that source — not our own verdict.
Effects on the breastfed infant
Weekly methotrexate 25 mg subcutaneously begun a nursing mother on day 151 postpartum. The estimated intake of the infant at that time was 3.4 mcg/kg in the first 24 hours after administration. The mother continued to breastfeed (extent not stated) for an additional 9 months while receiving subcutaneous methotrexate 25 mg weekly. No adverse effects were noted in the infant.[ 14 ] Three postpartum women were erroneously dispensed methotrexate 2.5 mg daily instead of methylergonovine. They took methotrexate daily for 5, 13 and 15 days, respectively, while they were breastfeeding (extent not stated). Although all of the women developed toxicity and required hospitalization, none of their infants had clinically observable complications.[ 15 ]
Effects on milk supply
Relevant published information was not found as of the revision date.
Levels in milk
Methotrexate is partially metabolized to the active metabolite, 7-hydroxymethotrexate, which is detectable in breastmilk. Maternal Levels. One patient who was 1 month postpartum was given 22.5 mg (15 mg/square meter) methotrexate daily by mouth for choriocarcinoma. Milk was collected at various times of the first 12 days of therapy and measured using an old bioassay. A peak milk level of 2.3 mcg/L occurred 10 hours after the first dose. However, the milk level was relatively constant during the period from 4 to 10 hours after the dose, after which it began to drop. Peak milk levels on the second and third days of administration were 2.7 mcg/L. The authors estimated that a cumulative amount of 0.32 mcg would be excreted in milk during the first 12 hours after this dose.[ 12 ] Assuming a maternal weight of 60 kg and using the highest milk level, the worst-case relative infant dose would be about 0.1% A woman was given a single intramuscular dose of 65 mg (50 mg/square meter) of methotrexate for ectopic pregnancy. Six milk samples were obtained from 1 to 24 hours after the dose. Methotrexate was undetectable ( 22.7 mcg/L) in all milk samples.[ 13 ] A woman with rheumatoid arthritis received hydroxychloroquine, sulfasalazine and prednisone 10 mg daily during pregnancy and postpartum. On day 151 postpartum, methotrexate 25 mg was given subcutaneously. Breastmilk samples were obtained at 2, 12 and 24 hours after the dose. Milk levels were 0.05 micromolar (22.7 mcg/L) in all samples, which was considered detectable, but not quantifiable. A fully breastfed infant would receive 3.4 mcg/kg in the first 24 hours after administration, or about 1% of the weight-adjusted maternal dosage.[ 14 ] Two lactating women receiving subcutaneous methotrexate 25 mg once weekly donated 4 to 7 milk samples over a 1-week period between doses. Peak breastmilk methotrexate milk concentrations occurred between 1 and 12 hours after the dose and were 4 nmol/L (1.8 mcg/L). Peak breastmilk milk conce
Alternatives LactMed lists
Source: NIH LactMed (National Library of Medicine).
Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.