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Drugs and Lactation Database (LactMed) [Internet]. Bethesda (MD): National Library of Medicine (US); 2006-.

Cover of Drugs and Lactation Database (LactMed)

Drugs and Lactation Database (LactMed) [Internet].

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Last Revision: October 31, 2018.

Estimated reading time: 1 minute

CASRN: 26171-23-3

Chemical structure

Drug Levels and Effects

Summary of Use during Lactation

Because of the low levels of tolmetin in breastmilk and its short half-life, it is unlikely to adversely affect the breastfed infant. However, because there is no published experience with breastfeeding during tolmetin use, other agents may be preferred, especially while nursing a newborn or preterm infant.

Drug Levels

Maternal Levels. Following a single 400 mg dose of tolmetin in a woman who was 2 months postpartum, peak milk levels occurred at 40 and 60 minutes after the dose in the right and left breasts, respectively, and averaged 160 mcg/L. The drug was undetectable (<30 mcg/L) in milk by 5 hours after the dose and its half-life in breastmilk was 1.54 hours.[1]

Using the peak milk level data, the estimated maximum intake of an exclusively breastfed infant would be 0.4% of the maternal weight-adjusted dosage.

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.


Sagraves R, Waller ES, Goehrs HR. Tolmetin in breast milk. Drug Intell Clin Pharm. 1985;19:55-6. Letter. [PubMed: 3967576]

Substance Identification

Substance Name


CAS Registry Number


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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