METHENAMINE HIPPURATE
Background and Date of Approval
Methenamine, also called hexamethylenetetramine, was first synthesised in the late 19th century. It was later combined with hippuric acid to form methenamine hippurate, which enhances the drug's effectiveness in acidic urine. This formulation has been widely used since the mid-20th century as a urinary antiseptic for prevention of recurrent urinary tract infections (UTIs). Methenamine hippurate tablets received FDA approval in the United States in 1976 for prophylaxis of recurrent UTIs. It remains in clinical use as a non-antibiotic option to reduce the risk of antibiotic resistance in long-term UTI management.
Uses
Prevention of recurrent urinary tract infections (UTIs) in adults and children. Long-term prophylaxis in patients with chronic or recurrent cystitis. An alternative to antibiotics for preventing UTIs, particularly in patients prone to resistance.
Side Effects
Serious (rare): Allergic reactions (rash, itching, swelling, difficulty breathing). Painful urination, blood in urine (signs of bladder irritation). Severe gastrointestinal upset. Rare cases of crystalluria or kidney irritation. Common: Nausea. Upset stomach. Rash or mild skin reaction. Burning sensation in the bladder (mild, usually temporary).
Warnings
Not for active UTI treatment; must clear infection first with antibiotics. Liver impairment: Use with caution, as methenamine breakdown may be altered. Kidney impairment: Contraindicated in severe renal insufficiency or dehydration. Metabolic acidosis: Avoid use in patients with severe dehydration or metabolic disorders that affect acid-base balance. Drug interactions: Avoid with sulfonamides (can form insoluble precipitates in urine).
Precautions
Maintain an acidic urine environment (your doctor may suggest dietary changes or vitamin C). Drink adequate fluids to support kidney and bladder health. Inform your doctor if you have liver disease, asthma, or lung conditions, as methenamine can rarely cause lung irritation. Safe for long-term use in most patients, but regular monitoring of urine pH and kidney function is recommended. Not recommended in pregnancy unless clearly needed.
References
Naber KG, Cho YH, Matsumoto T, Schaeffer AJ. “Immunoactive prophylaxis of recurrent urinary tract infections: a meta-analysis,” International Journal of Antimicrobial Agents, 2009 https://www.sciencedirect.com/science/article/abs/pii/S0924857909003112?via%3Dihub Lee BS, Bhuta T, Simpson JM, Craig JC. “Methenamine hippurate for preventing urinary tract infections,” Cochrane Database of Systematic Reviews, [Updated 2012] https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003265.pub3/full National Institute for Health and Care Excellence (NICE). “Urinary tract infection (lower): antimicrobial prescribing,” NICE guideline [NG109], 2018 https://www.nice.org.uk/guidance/ng109
Frequently Asked Questions
What is Methenamine Hippurate used for?
It is used for preventing recurrent urinary tract infections, not for treating an active infection.
What is the right way to use Methenamine Hippurate?
Usually taken twice daily with water, as prescribed by your doctor.
Can Methenamine Hippurate replace antibiotics?
It is not an antibiotic, but it helps prevent UTIs and may reduce the need for long-term antibiotics.
Do I need urine tests while taking this medicine?
Yes. Your doctor may check your urine pH and monitor for infection recurrence.
Can children take Methenamine Hippurate?
Yes, it is sometimes prescribed for children with recurrent UTIs, under medical supervision.