U.S. flag

An official website of the United States government

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

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].

Show details

Methenamine Mandelate

Last Revision: January 18, 2021.

Estimated reading time: 1 minute

CASRN: 587-23-5

image 134976170 in the ncbi pubchem database

Drug Levels and Effects

Summary of Use during Lactation

Both methenamine and mandelic acid pass into milk in small quantities. Methenamine mandelate appears 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]

Six mothers were given mandelic acid 3 grams orally 4 times daily, a dose far in excess of that contained in a typical dose of methenamine mandelate. The authors estimated that their exclusively breastfed infants received an average 273 mg of mandelic acid daily in breastmilk. This amounted to an average daily dosage of 86 mg/kg in the 6 infants, which is about 48% of the adult dosage.[2]

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]

Six infants were allowed to nurse during maternal ingestion of the large daily dosage of 12 grams of mandelic acid. There was no clinical or laboratory evidence of harm to the infants.[2]

Effects on Lactation and Breastmilk

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

Alternate Drugs to Consider

Methenamine Hippurate


Allgén LG, Holmberg G, Persson B, et al. Biological fate of methenamine in man. Acta Obstet Gynecol Scand. 1979;58:287–93. [PubMed: 484222]
Berger H. Excretion of mandelic acid in breast milk. Am J Dis Child. 1941;61:256–61.

Substance Identification

Substance Name

Methenamine Mandelate

CAS Registry Number


Drug Class

Breast Feeding


Anti-Infective Agents, Urinary

Antibacterial 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.


Related information

Similar articles in PubMed

See reviews...See all...

Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...