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Methenamine Side Effects

Medically reviewed by Last updated on Sep 20, 2023.

Applies to methenamine: oral tablet.

Serious side effects of Methenamine

Along with its needed effects, methenamine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking methenamine:

Less common


Other side effects of Methenamine

Some side effects of methenamine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

For Healthcare Professionals

Applies to methenamine: compounding powder, oral suspension, oral tablet.


This drug was generally well tolerated. Minor side effects have been reported in less than 3.5% of patients and were reversible when the drug was stopped.[Ref]


Uncommon (0.1% to 1%): Rash, pruritus

Frequency not reported: Generalized skin rash[Ref]


Uncommon (0.1% to 1%): Gastric irritation

Frequency not reported: Nausea, vomiting, upset stomach, stomatitis, gastrointestinal disturbances, diarrhea, abdominal cramping[Ref]


Uncommon (0.1% to 1%): Bladder irritation

Frequency not reported: Dysuria, hematuria, urinary frequency, albuminuria[Ref]

High doses have been associated with albuminuria, gross hematuria, bladder irritation, and painful/frequent micturition.[Ref]


Frequency not reported: Elevated AST, elevated ALT[Ref]


Frequency not reported: Hypersensitivity reactions[Ref]


Frequency not reported: Anorexia


Frequency not reported: Anterior uveitis[Ref]


1. (2002) "Product Information. Hiprex (methenamine)." Hoechst Marion Roussel

2. Cerner Multum, Inc. "UK Summary of Product Characteristics."

3. Cerner Multum, Inc. "Australian Product Information."

4. Brumfitt W, Hamilton-Miller J, Gargan R, Cooper J, Smith GW (1983) "Long-term prophylaxis of urinary infections in women: comparative trial of trimethoprim, methenamine hippurate and topical povidone-iodine." J Urol, 130, p. 1110-4

5. Gleckman R, Alvarez S, Joubert D, Matthews S (1979) "Drug therapy reviews: methenamine mandelate and methenamine hippurate." Am J Hosp Pharm, 36, p. 1509-12

6. Australian Drug Evaluation Committee (1972) "Adverse effects of drugs commonly used in the treatment of urinary tract infection." Med J Aust, 1, p. 435-8

7. (2002) "Product Information. Mandelamine (methenamine)." Parke-Davis

8. Brumfitt W, Cooper J, Hamilton-Miller J (1981) "Prevention of recurrent urinary infections in women: a comparative trial between nitrofurantoin and methenamine hippurate." J Urol, 126, p. 71-4

9. Kolker RJ (1991) "Medication-induced bilateral anterior uveitis." Arch Ophthalmol, 109, p. 1343

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.