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Drugs and Lactation Database (LactMed) [Internet].

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Mefenamic Acid

Last Revision: February 7, 2019.

Estimated reading time: 1 minute

CASRN: 61-68-7

Chemical structure

Drug Levels and Effects

Summary of Use during Lactation

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.

Drug Levels

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]

Effects in Breastfed Infants

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

Effects on Lactation and Breastmilk

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

References

1.
Buchanan RA, Eaton CJ, Koeff ST et al. The breast milk excretion of mefenamic acid. Curr Ther Res. 1968;10:592-6. [PubMed: 4973976]

Substance Identification

Substance Name

Mefenamic Acid

CAS Registry Number

61-68-7

Drug Class

  • Breast Feeding
  • Analgesic Agents
  • Nonsteroidal Antiinflammatory Agents

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.

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