Methenamine has long been studied as a non-antibiotic option to help prevent urinary tract infections (UTIs). The idea is simple: when urine is acidic, methenamine breaks down into formaldehyde, which creates a bacteriostatic effect. Unlike antibiotics, it doesn’t lead to the evolution of resistance among the harmful germs that live in the bladder, which is an increasingly important consideration in an era of rising antimicrobial resistance, the long time periods over which people may experience urinary tract infections, and the possibility that with a long history of antibiotics use, more and more of those antibiotics will lose effectivness and no longer be treatment options for infections.
Why People Are Interested in Methenamine
For individuals with frequent UTIs, especially women with recurrent infections, methenamine offers some clear benefits. Studies and systematic reviews show that methenamine is generally well tolerated, with few side effects beyond occasional gastrointestinal upset or headache. Importantly, multiple randomized trials demonstrate that methenamine performs as well as antibiotics for preventing recurrent UTIs in the general population, while avoiding the problem of selecting for resistant bacteria.[1–5]
Guidelines have taken notice. The American Urological Association, Canadian Urological Association, and Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (AUA/CUA/SUFU) all highlight methenamine as a promising non-antibiotic prophylactic option for women with recurrent uncomplicated UTI—particularly when antibiotic stewardship is a priority.[6]
Where the Evidence Falls Short
The picture changes for people with neurogenic bladder who perform clean intermittent catheterization (CIC). Evidence in this group is limited and less encouraging. The AUA/SUFU guideline on neurogenic lower urinary tract dysfunction (NLUTD) notes that oral antimicrobial prophylaxis (preventative antibiotics use) may be considered for recurrent UTIs in CIC users, but this recommendation applies to antibiotics, not methenamine, and is conditional due to resistance concerns.[7]
Cochrane reviews and subsequent studies reinforce this caution. Methenamine does not appear effective for patients with neuropathic bladder (such as due to a spinal cord injures), renal tract abnormalities, or other structural issues common in neurogenic bladder. Factors such as altered urinary pH (often elevated compared to non-catheterizing individuals), frequent bladder emptying, chronic bacteriuria, and biofilm formation limit methenamine’s ability to generate enough formaldehyde in the bladder to prevent infections.[8–9]
Practical Considerations
Even when methenamine is appropriate, its effectiveness depends on the right conditions. Urine must remain acidic, which sometimes requires co-administration of acidifying agents such as ascorbic acid. Regular bladder emptying can also reduce the contact time needed for methenamine to work, which may help explain why results are inconsistent in CIC users.
The Bottom Line
Methenamine is a reasonable non-antibiotic alternative for UTI prevention in patients with otherwise intact urinary tracts. It’s supported by recent trials and guideline endorsements for women with recurrent UTIs, where minimizing antibiotic use is critical. But for people with neurogenic bladder who perform clean intermittent catheterization, current evidence does not support methenamine as an effective strategy. For this group, antibiotics remain the only pharmacologic prophylaxis with evidence of benefit—though they must be used carefully, with attention to resistance risk.[7–9]
Ongoing research is needed to clarify the role of non-antibiotic strategies—including bladder irrigation, probiotics, and immunoprophylaxis—in CIC users. For now, methenamine should be viewed as a tool with promise, but only in select populations.
As always, consult your doctor before taking any supplements to potentially reduce UTIs. Methenamine is sold under the trade names Antihydral, Hiprex, Urex, Urotropin, and many others.
References
- Davidson SM, Brown JN, Nance CB, Townsend ML. Use of Methenamine for Urinary Tract Infection Prophylaxis: Systematic Review of Recent Evidence. Int Urogynecol J. 2024;35(3):483-489. doi:10.1007/s00192-024-05726-2.
- Li JM, Cosler LE, Harausz EP, Myers CE, Kufel WD. Methenamine for Urinary Tract Infection Prophylaxis: A Systematic Review. Pharmacotherapy. 2024;44(2):197-206. doi:10.1002/phar.2895.
- Nelson Z, Aslan AT, Beahm NP, et al. Guidelines for the Prevention, Diagnosis, and Management of Urinary Tract Infections in Pediatrics and Adults: A WikiGuidelines Group Consensus Statement. JAMA Netw Open. 2024;7(11):e2444495. doi:10.1001/jamanetworkopen.2024.44495.
- Heltveit-Olsen SR, Arnljots ES, Sundvall PD, et al. Methenamine Hippurate as Prophylaxis for Recurrent Urinary Tract Infections in Older Women – A Triple-Blind, Randomised, Placebo-Controlled, Phase IV Trial (ImpresU). Clin Microbiol Infect. 2025;:S1198-743X(25)00344-1. doi:10.1016/j.cmi.2025.07.006.
- Brubaker L, Carberry C, Nardos R, Carter-Brooks C, Lowder JL. American Urogynecologic Society Best-Practice Statement: Recurrent Urinary Tract Infection in Adult Women. Female Pelvic Med Reconstr Surg. 2018;24(5):321-335. doi:10.1097/SPV.0000000000000550.
- Anger JT, Bixler BR, Holmes RS, et al. Updates to Recurrent Uncomplicated Urinary Tract Infections in Women: AUA/CUA/SUFU Guideline. J Urol. 2022;208(3):536-541. doi:10.1097/JU.0000000000002860.
- Ginsberg DA, Boone TB, Cameron AP, et al. The AUA/SUFU Guideline on Adult Neurogenic Lower Urinary Tract Dysfunction: Treatment and Follow-Up. J Urol. 2021;206(5):1106-1113. doi:10.1097/JU.0000000000002239.
- Lee BS, Bhuta T, Simpson JM, Craig JC. Methenamine Hippurate for Preventing Urinary Tract Infections. Cochrane Database Syst Rev. 2012;10:CD003265. doi:10.1002/14651858.CD003265.pub3.
- Vainrub B, Musher DM. Lack of Effect of Methenamine in Suppression of, or Prophylaxis Against, Chronic Urinary Infection. Antimicrob Agents Chemother. 1977;12(5):625-629. doi:10.1128/AAC.12.5.625.