Mefenamic Acid

Drug Levels and Effects:

Summary of Use during Lactation:

If mefenamicacidis required by the mother, it is not a reason to discontinue breastfeeding. Because there is little published experience with mefenamicacidduring breastfeeding and it is potentially toxic, other agents may be preferred, especially while nursing a newborn or preterm infant.

Drug Levels:

Maternal Levels.

Ten postpartum women received a 500 mg loading dose of mefenamicacidfollowed by 250 mg orally 3 times daily through the fourth postpartum day. Mefenamicacidand its metabolites were measured using an old, insensitive assay method. Milk samples taken 2 hours after the first dose of each day found average mefenamicacidmilk 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 mefenamicacidfollowed 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]

Effects in Breastfed Infants:

Ten newborns were breastfed for 4 days during maternal intake of mefenamicacid. No mention was made of infant side effects or lack thereof.[1]

Possible Effects on Lactation:

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

Alternate Drugs to Consider:



1. Buchanan RA, Eaton CJ, Koeff ST et al. The breast milk excretion of mefenamicacid. Curr Ther Res. 1968;10:592-6. PMID:4973976

Substance Identification:

Substance Name:


CAS Registry Number:


Drug Class:

  • Analgesic Agents

  • Nonsteroidal Antiinflammatory Agents

  • Administrative Information:

    LactMed Record Number:


    Last Revision Date:

    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.