Summary of Use during Lactation

Methenamine passes into milk in small quantities and appears safe 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

Methenamine Mandelate

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 Name

Methenamine Hippurate

CAS Registry Number

5714-73-8

Drug Class

Breast Feeding

Lactation

Anti-Infective Agents, Urinary