Research
Methenamine hippurate for Bladder Health: Evidence, Interactions and Cautions
Methenamine hippurate is an ingredient used in bladder supplements marketed to women. Below is what it has actually been studied for, how strong that evidence is, the drug interactions and cautions on record, and the primary source our grade rests on — all drawn from the HerWellReport ingredient dataset.
Also sold as: Hiprex; hexamine hippurate; methenamine
What the evidence says about Methenamine hippurate
This is a prescription-only medicine, not a supplement, and it should never be grouped with over-the-counter bladder products. The ALTAR non-inferiority randomised trial in UK NHS clinics randomised 240 women to methenamine hippurate or daily antibiotic prophylaxis for 12 months: UTI incidence was 1.38 episodes per person-year on methenamine against 0.89 on antibiotics, and that 0.49 difference stayed inside the pre-specified non-inferiority limit of one episode per year, with low and comparable adverse event rates in both arms. NICE's evidence review rated the underlying evidence very low quality because of small samples, missing data and inconsistency, and the AUA/CUA/SUFU recurrent UTI guideline says clinicians may offer it (conditional recommendation, evidence grade C). It works by releasing formaldehyde in acidic urine, so anything that alkalinises your urine undermines it.
The grade "moderate" means: moderate — Randomised trials exist for this use but they are few, small, short or mixed. Grades are explained in full on our methodology page.
Read the primary source this grade rests on (opens in a new tab).
Methenamine hippurate drug interactions
- Sulphonamides (must not be given concurrently because of the risk of crystalluria)
- urinary alkalinising agents such as potassium citrate mixtures
- acetazolamide
Who should be careful with Methenamine hippurate
- Prescription-only medicine in the UK, not a food supplement
- contraindicated in severe renal failure (creatinine clearance or GFR under 10 ml/min), severe dehydration, metabolic acidosis, gout and hepatic dysfunction
- preferably avoided in pregnancy
- can cause gastric and bladder irritation, nausea, vomiting, rash and itching
Read more on HerWellReport
- Best Bladder Control Supplements for Women (2026): What’s Actually in Them
- Cystex Review (2026): The Cranberry Dose It Won’t Disclose
This entry is generated from row "Methenamine hippurate" of the HerWellReport ingredient dataset (v2.1, updated 2026-09-23). The dataset is free to reuse under CC BY 4.0 — how to cite it. Ingredient evidence is not evidence for any finished product, and nothing here is medical advice.