Urex Side Effects
Generic name: methenamine
Medically reviewed by Drugs.com. Last updated on Aug 29, 2020.
Note: This document contains side effect information about methenamine. Some of the dosage forms listed on this page may not apply to the brand name Urex.
For the Consumer
Applies to methenamine: oral tablet
Side effects requiring immediate medical attention
Along with its needed effects, methenamine (the active ingredient contained in Urex) 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:
- Blood in urine
- lower back pain
- pain or burning while urinating
Side effects not requiring immediate medical attention
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:
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
Uncommon (0.1% to 1%): Bladder irritation
Frequency not reported: Elevated AST, elevated ALT[Ref]
Frequency not reported: Hypersensitivity reactions[Ref]
Frequency not reported: Anorexia
1. "Product Information. Hiprex (methenamine)." Hoechst Marion-Roussel Inc, Kansas City, MO.
2. Cerner Multum, Inc. "Australian Product Information." O 0
3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
4. Gleckman R, Alvarez S, Joubert D, Matthews S "Drug therapy reviews: methenamine mandelate and methenamine hippurate." Am J Hosp Pharm 36 (1979): 1509-12
5. "Product Information. Mandelamine (methenamine)." Parke-Davis, Morris Plains, NJ.
6. Australian Drug Evaluation Committee "Adverse effects of drugs commonly used in the treatment of urinary tract infection." Med J Aust 1 (1972): 435-8
7. Brumfitt W, Hamilton-Miller J, Gargan R, Cooper J, Smith GW "Long-term prophylaxis of urinary infections in women: comparative trial of trimethoprim, methenamine hippurate and topical povidone-iodine." J Urol 130 (1983): 1110-4
8. Brumfitt W, Cooper J, Hamilton-Miller J "Prevention of recurrent urinary infections in women: a comparative trial between nitrofurantoin and methenamine hippurate." J Urol 126 (1981): 71-4
9. Kolker RJ "Medication-induced bilateral anterior uveitis." Arch Ophthalmol 109 (1991): 1343
More about Urex (methenamine)
- During Pregnancy or Breastfeeding
- Dosage Information
- Drug Images
- Drug Interactions
- Generic Availability
- Drug class: urinary anti-infectives
Related treatment guides
Some side effects may not be reported. You may report them to the FDA.