Methenamine Mandelate


Methenamine is used to prevent or control returning urinary tract infections caused by bacteria. It is not used to treat an active infection. Antibiotics must be used first to treat and cure the infection. Methenamine is a drug that stops the growth of bacteria in urine. 

When the urine is acidic, methenamine turns into formaldehyde to kill the bacteria.This drug is effective only against bacterial infections in the urinary tract. Unnecessary use or misuse of any antibacterial drug can lead to its decreased effectiveness.

How to use Methenamine Mandelate

This medication is taken by mouth (oral).

Methenamine works better if your urine is more acidic. To increase urine acidity (such as by taking vitamin C/drinking cranberry juice, limiting foods that decrease acidity/increase alkalinity such as milk products/most fruits, adjusting alkalinizing medications) makes the drug effecive.

This medication must be taken at the same time(s) every day.

 Side effects of Methenamine Mandelate

Side Effects


Nausea, vomiting, diarrhea, abdominal cramps, and loss of appetite may occur.

Painful or difficult urination may occur with methenamine, then it may require to lower your dose of methenamine or change treatment to make your urine less acidic.

Taking higher than recommended doses of methenamine may cause bladder irritation, painful/frequent urination, and bloody/pink urine.

Serious side effects, including: mouth sores, unusual headache, ringing in the ears, muscle cramps, swelling of the arms/legs.

 A very serious allergic reaction to this drug is rare. However, rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
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