CASRN: 100-97-0
Drug Levels and Effects
Summary of Use during Lactation
Both the hippurate and mandelate salts of methenamine pass into milk in small quantities and appear acceptable to use, even while nursing a newborn.
Drug Levels
Maternal Levels. Six mothers nursing newborn infants were given methenamine hippurate 1 gram orally. Five hours after the dose, a mean methenamine concentration of 7 mg/L was found in milk. In two other women, milk concentrations averaged 9.1 mg/L at 2 to 3 hours after a 1 gram dose of methenamine hippurate orally and 4.3 mg/L at 6 to 7 hours after the dose. Based on the amount of milk ingested, the authors calculated the dose the infants received to be 0.05 to 0.1 mg/kg, which is about 1% of the adult dose.[1]
Infant Levels. Relevant published information was not found as of the revision date.
Effects in Breastfed Infants
Four newborn infants were allowed to breastfeed in one study after a maternal dose of 1 gram of methenamine hippurate. No adverse effects were reported.[1]
Effects on Lactation and Breastmilk
Relevant published information was not found as of the revision date.
Alternate Drugs to Consider
References
- 1.
- Allgén LG, Holmberg G, Persson B, et al. Biological fate of methenamine in man. Acta Obstet Gynecol Scand. 1979;58:287–93. [PubMed: 484222]
Substance Identification
Substance Name
Methenamine
CAS Registry Number
100-97-0
Drug Class
Breast Feeding
Lactation
Anti-Infective Agents, Urinary
Antibacterial Agents
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Publication Details
Publication History
Last Revision: January 18, 2021.
Copyright
Attribution Statement: LactMed is a registered trademark of the U.S. Department of Health and Human Services.
Publisher
National Institute of Child Health and Human Development, Bethesda (MD)
NLM Citation
Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006-. Methenamine. [Updated 2021 Jan 18].