Is Mefenamic Acid safe while breastfeeding?

Here is what LactMed, the Drugs and Lactation Database published by the U.S. National Institute of Child Health and Human Development (NICHD), reports about Mefenamic Acid. The text below is quoted from that source — it is not our own verdict.

Summary of use during breastfeeding

Because there is little published experience with mefenamic acid during breastfeeding and it is potentially toxic, other agents may be preferred, especially while nursing a newborn or preterm infant.

Effects on the breastfed infant

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

Effects on milk supply

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

Levels in milk

Maternal Levels. Ten postpartum women received a 500 mg loading dose of mefenamic acid followed by 250 mg orally 3 times daily through the fourth postpartum day. Mefenamic acid and its metabolites were measured using an old, insensitive assay method. Milk samples taken 2 hours after the first dose of each day found average mefenamic acid milk levels of 170 mcg/L (range 30 to 660 mcg/L), although these levels might be inaccurate because the concentration measured in blank milk samples in this study was 200 mcg/L and potentially active metabolites were not measured.[1]

Infant Levels. Ten postpartum women received a 500 mg loading dose of mefenamic acid followed by 250 mg orally 3 times daily. Infant serum and urine specimens were obtained one hour after nursing on the afternoon of the fourth day. Only 3 of the 10 infants had blood levels at or above the blank level of the assay (10 mg/L). Average urine recovery was similar to the blank level. Five of the 10 infants had urine levels greater than blank urine.[1]

Alternatives LactMed lists

Mefenamic Acid in pregnancy

LactMed covers breastfeeding only. For what the NHS and the US prescribing label say about pregnancy, see:

Source: Drugs and Lactation Database (LactMed), National Institute of Child Health and Human Development (NICHD), via NCBI Bookshelf, record “Mefenamic Acid” (LM166). LactMed on NCBI Bookshelf. LactMed is a registered trademark of the U.S. Department of Health and Human Services.

Educational summary of an authoritative source — not medical advice. Never start, stop, or change a medicine while breastfeeding without confirming with your doctor.