From the Guidelines
The recommended dose of methenamine hippurate for preventing urinary tract infections (UTIs) in adults is 1 gram taken orally twice daily, as supported by the most recent and highest quality study 1. For children, the dosage is typically adjusted based on weight, with approximately 500 mg twice daily for children 6-12 years old. Treatment duration for UTI prevention can be long-term, with many patients taking methenamine hippurate for months or even years under medical supervision. The medication works by converting to formaldehyde in acidic urine, creating an environment hostile to bacterial growth. For optimal effectiveness, maintaining urine acidity is important, which may require concurrent use of vitamin C (ascorbic acid) or cranberry products. Patients should take the medication with plenty of water and maintain adequate hydration throughout the day. Common side effects include stomach upset, nausea, and bladder irritation. Methenamine hippurate is generally well-tolerated for long-term use because it works locally in the urinary tract rather than systemically throughout the body, making it suitable for ongoing prophylaxis in patients with recurrent UTIs, as noted in a recent consensus statement 1. Key considerations for the use of methenamine hippurate include its noninferiority to antibiotics for UTI prevention in women aged 18 years and older, as demonstrated in a systematic review and nonblinded RCT 1. Additionally, methenamine hippurate is an appealing antimicrobial-sparing intervention to reduce UTIs in patients without incontinence and a fully functional bladder, as outlined in guidelines for UTI prevention 1. Overall, methenamine hippurate is a viable option for UTI prevention, particularly in patients seeking alternatives to prophylactic antibiotics.
From the FDA Drug Label
DOSAGE AND ADMINISTRATION 1 Tablet (1.0 g) twice daily (morning and night) for adults and pediatric patients over 12 years of age. 1/2 to 1 tablet (0.5 to 1.0 g) twice daily (morning and night) for pediatric patients 6 to 12 years of age. The recommended dose of Methenamine hippurate for preventing Urinary Tract Infections (UTIs) is:
- 1 tablet (1.0 g) twice daily for adults and pediatric patients over 12 years of age
- 1/2 to 1 tablet (0.5 to 1.0 g) twice daily for pediatric patients 6 to 12 years of age. The treatment duration is not explicitly stated in the drug label, therefore no conclusion can be drawn regarding the treatment duration 2.
From the Research
Dosage and Treatment Duration of Methenamine Hippurate
- The recommended dose of methenamine hippurate for preventing Urinary Tract Infections (UTIs) is 1g twice daily 3, 4.
- The treatment duration of methenamine hippurate for preventing UTIs can range from 6 months to 12 months 3, 4, 5.
- A study found that methenamine hippurate was effective in reducing UTI frequency, antibiotic use, and hospitalization in renal transplant recipients, with a median follow-up of 365 days 6.
Efficacy of Methenamine Hippurate
- Methenamine hippurate has been shown to be non-inferior to antibiotic prophylaxis in preventing recurrent UTIs in women 3, 5.
- A meta-analysis found that methenamine hippurate was effective in preventing UTIs, with a relative risk of 1.15 (95% CI 0.96,1.38) compared to antibiotic prophylaxis 5.
- Another study found that methenamine hippurate was as effective as trimethoprim in preventing UTIs, with a recurrence rate of 65% in both groups 4.
Safety and Adverse Effects
- Methenamine hippurate has been shown to be well-tolerated, with few adverse effects reported 3, 6, 4.
- A study found that methenamine hippurate had a lower rate of antibiotic resistance compared to antibiotic prophylaxis 3.
- However, another study found that methenamine hippurate was associated with a higher rate of multidrug resistance in E. coli isolated from perineal swabs after treatment 3.