Hiprex (methenamine hippurate) is an oral antimicrobial used to prevent and suppress urinary tract infections (UTIs). Hiprex works by releasing formaldehyde in the acidic environment of the bladder, which acts as a bactericidal agent.
Best time to take Hiprex
Hiprex is typically taken twice daily (morning and evening), with or after meals. Taking Hiprex with food or after food reduces the risk of irritation to the intestine or stomach lining.
This timing helps ensure the steady urinary excretion of the active component, methenamine, for formaldehyde production in the bladder, where it is required.
Why do I need to stay hydrated when taking Hiprex?
Unless otherwise advised by a healthcare practitioner, to ensure the action of Hiprex, keeping the flow of fluids through your urinary system is important to keep the Hiprex moving where it is supposed to act: the urinary tract.
But isn’t the stomach acidic too? Does Hiprex produce formaldehyde in the stomach?
Hiprex doesn’t produce formaldehyde in the stomach, especially with food present, as formaldehyde is only produced with persistent low pH and in the presence of water, as found in the bladder.
The stomach could theoretically allow formaldehyde formation, but it tends to take a bit longer. Food in the stomach raises gastric pH by diluting stomach acid, and when food gets to the intestine, it is also alkaline. Gastrointestinal transit time is usually too quick.
Research shows that gastric formaldehyde generation is negligible (so not nothing), but the majority is produced in acidic urine.
The importance of acidic urine when taking Hiprex
The acidity requirement is really important. Some bacteria cause the urine to become less acidic/more alkaline, which is bad news for the efficacy of Hiprex. Ensure the use of a urinary acidifier such as vitamin C (taken away from Hiprex to avoid gastric formaldehyde production!).
To determine your urinary pH, get urinary pH testing strips with the range 5 – 9. You want the urinary pH to be around 5.5 or under for the best effect. Test urine regularly to get an idea of what modifies your urinary pH, for example, certain foods, drinks, first thing in the morning, etc.
Getting support for chronic UTI
My Vagina’s clinical naturopaths work with people with chronic UTI daily and can help you resolve this on a more long-lasting basis.
Our experienced practitioners use non-drug treatments that can work concurrently with antibiotics as needed, using an integrative framework for care. We aim to reduce antibiotic use as much as possible with effective solutions for urinary tract infections.
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References1–4
- 1.Harding C, Mossop H, Homer T, et al. Alternative to prophylactic antibiotics for the treatment of recurrent urinary tract infections in women: multicentre, open label, randomised, non-inferiority trial. BMJ. Published online March 9, 2022:e068229. doi:10.1136/bmj-2021-0068229
- 2.Li JM, Cosler LE, Harausz EP, Myers CE, Kufel WD. Methenamine for urinary tract infection prophylaxis: A systematic review. Pharmacotherapy. Published online November 28, 2023:197-206. doi:10.1002/phar.2895
- 3.Heltveit-Olsen SR, Sundvall PD, Gunnarsson R, et al. Methenamine hippurate to prevent recurrent urinary tract infections in older women: protocol for a randomised, placebo-controlled trial (ImpresU). BMJ Open. Published online November 2022:e065217. doi:10.1136/bmjopen-2022-065217
- 4.Bakhit M, Krzyzaniak N, Hilder J, Clark J, Scott AM, Mar CD. Use of methenamine hippurate to prevent urinary tract infections in community adult women: a systematic review and meta-analysis. Br J Gen Pract. Published online January 17, 2021:e528-e537. doi:10.3399/bjgp.2020.0833