Methenamine and Breastfeeding

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 in milk and infant serum

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.

Alternative drugs to consider

Methenamine Hippurate, Methenamine Mandelate

References

1. AllgénLG HolmbergG PerssonB Biological fate of methenamine in man. Acta Obstet Gynecol Scand 1979 58 287 93 484222