Last update Feb. 11, 2019


Low Risk

Possibly safe. Probably compatible. Mild risk possible. Follow up recommended. Read the Comment.

An antibacterial used in the long-term prophylaxis and treatment of recurrent lower urinary tract infections (bladder) and asymptomatic bacteriuria.
Oral administration 2 to 4 times a day.

It is excreted in breastmilk in clinically insignificant amounts and no problems have been observed in infants whose mothers were taking it (Allgen 1979).

Several expert authors consider it safe or probably safe to use this medication during breastfeeding (Lactmed 2018, Hale 2017 p 624, Briggs 2017).

Exposure can be minimized by waiting to breastfeed three hours after taking the drug (Mactal 2001).


We do not have alternatives for Methenamine.

Suggestions made at e-lactancia are done by APILAM team of health professionals, and are based on updated scientific publications. It is not intended to replace the relationship you have with your doctor but to compound it. The pharmaceutical industry contraindicates breastfeeding, mistakenly and without scientific reasons, in most of the drug data sheets.

Jose Maria Paricio, Founder & President of APILAM/e-Lactancia

Your contribution is essential for this service to continue to exist. We need the generosity of people like you who believe in the benefits of breastfeeding.

Thank you for helping to protect and promote breastfeeding.

José María Paricio, founder of e-lactancia.

Other names

Methenamine is also known as

Methenamine in other languages or writings:


Methenamine belongs to this group or family:


Main tradenames from several countries containing Methenamine in its composition:


Variable Value Unit
Molecular weight 140 daltons
Tmax 1 - 2 hours
3 - 4 hours
M/P ratio 1 -
Theoretical Dose 0.65 - 1.37 mg/Kg/d
Relative Dose 3.9 - 8.2 %


  1. LactMed. Methenamine. Drugs and Lactation Database. 2018 Abstract
  2. Hale TW, Rowe HE. Medications & Mothers' Milk. A Manual of Lactation Pharmacology. Springer Publishing Company. 2017
  3. Briggs GG, Freeman RK, Towers CV, Forinash AB. Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. Wolters Kluwer Health. Tenth edition (acces on line) 2015
  4. Mactal-Haaf C, Hoffman M, Kuchta A. Use of anti-infective agents during lactation, Part 3: Antivirals, antifungals, and urinary antiseptics. J Hum Lact. 2001 Abstract
  5. Allgén LG, Holmberg G, Persson B, Sörbo B. Biological fate of methenamine in man. Absorption, renal excretion and passage to umbilical cord blood, amniotic fluid and breast milk. Acta Obstet Gynecol Scand. 1979 Abstract

Total visits


Help us improve this entry

How to cite this entry

Do you need more information or did not found what you were looking for?

   Write us at

e-lactancia is a resource recommended by Academy of Breastfeeding Medicine - 2012 of United States of America

Would you like to recommend the use of e-lactancia? Write to us at corporate mail of APILAM