Methenamine hippurate
Brand names: Hiprex
Methenamine hippurate is a urinary antiseptic used for prophylaxis against recurrent lower urinary tract infection rather than for treating acute infection.
ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.
Clinical monograph
How it works
In acidic urine it is hydrolysed to formaldehyde, which exerts a non-specific antibacterial effect within the urinary tract.
Prescribing in practice
- It is for prophylaxis only and is not effective for treating an established acute urinary tract infection or upper urinary tract infection.
- Efficacy depends on acidic urine and adequate urinary formaldehyde, so it is unsuitable where urine is persistently alkaline or where there is significant urinary stasis.
- Avoid in significant renal or hepatic impairment, dehydration and metabolic disorders, and do not combine with sulfonamides, as advised in the SPC.
Monitoring
Monitoring is largely clinical, reviewing the frequency of breakthrough infections and tolerability rather than routine laboratory tests.
Counselling the patient
- This medicine helps prevent infections coming back; it is not a treatment for an active infection.
- Maintain a good fluid intake.
- Report bladder discomfort, rash or if infections keep occurring despite treatment.
Evidence & guidelines
The ALTAR trial supported methenamine hippurate as a non-antibiotic option for preventing recurrent urinary tract infection in women.
Reference: NICE NG112; ALTAR trial; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).
Related
Curated clinical cross-links plus same-class fallbacks.