methenamine hippurate at a glance
Medicine class
Urinary antibacterial or antiseptic
Usual role
Prevention of recurrent urinary infections after initial treatment
How it becomes active
Releases antibacterial formaldehyde in acidic urine
Tablet administration
The selected tablet may be halved or crushed and mixed with milk or fruit juice
What is methenamine hippurate used for?
The selected UK product is licensed for the following urinary-tract uses:
Maintenance after successful antibiotic treatment of an acute urinary infection
Long-term prevention of recurrent cystitis
Suppression of urinary infection with an indwelling catheter and reduction of catheter blockage
Prevention of infection introduced during urinary-tract instrumentation
Asymptomatic bacteriuria
How does methenamine hippurate work?
After absorption, methenamine is excreted through the kidneys. In acidic urine it slowly releases formaldehyde, which kills bacteria; hippuric acid helps maintain acidity and also inhibits urinary pathogens.
methenamine hippurate preparations and strengths
Tablet
Route: Oral
Strengths: 1 g
How to take methenamine hippurate
Take methenamine hippurate exactly as directed on the dispensing label. The selected tablet can be swallowed, halved, or crushed and taken with milk or fruit juice if swallowing is difficult.
Do not change or stop treatment without discussing it with the prescriber.
Check with a pharmacist before using products intended to make urine less acidic.
methenamine hippurate side effects
Common or expected effects
- Stomach irritation, nausea or vomiting
- Bladder irritation, including burning or pain when passing urine
- Rash or itching
- Diarrhoea or abdominal pain
Get urgent medical advice
- Signs of a severe allergic reaction, including facial or throat swelling, breathing difficulty, collapse or severe confusion
methenamine hippurate in pregnancy
Safety evidence in pregnancy is inadequate. The selected UK product information advises avoiding methenamine hippurate as a precaution, so pregnancy or plans for pregnancy should be discussed with the prescriber.
methenamine hippurate while breastfeeding
Methenamine passes into breast milk, but the selected UK product information considers the amount reaching the infant insignificant and permits breastfeeding. Seek individual advice if the infant is premature or unwell.
methenamine hippurate interactions
Check prescribed, over-the-counter and urinary-symptom products before combining them with methenamine hippurate.
Sulphonamide antibiotics
Concurrent use is contraindicated because crystals may form in the urine.
Urinary alkalising agents, including potassium citrate
They raise urinary pH and can prevent methenamine from working effectively.
Acetazolamide
It can reduce the required urinary acidity and should be avoided with methenamine hippurate.
Certain urine laboratory tests
Common questions about methenamine hippurate
Answers are fully visible for fast scanning and source review.
Is methenamine hippurate an antibiotic?
It is usually described as a urinary antibacterial or antiseptic rather than a conventional antibiotic. A UK trial supports it as a non-antibiotic preventive option for recurrent UTI in selected adult women.
Does methenamine hippurate treat an active UTI?
Its selected licence includes maintenance after successful initial antibiotic treatment. New or breakthrough symptoms need clinical assessment because antibiotics may be required for an active infection.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.