May 27, 2017
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Hiprex Patient Information Including Side Effects

Brand Names: Hiprex, Mandelamine, Urex

Generic Name: methenamine (Pronunciation: meh THEH na meen)

What is methenamine (Hiprex)?

Methenamine is a urinary antiinfective medicine. Methenamine fights bacteria in the urine and bladder.

Methenamine may be used to treat and prevent urinary tract infections.

Methenamine may also be used for purposes other than those listed here.

Hiprex 1 g

oval, yellow, imprinted with MERRELL 277

Mandelamine 0.5 g

oblong, brown, imprinted with 166

Mandelamine 1 g

oblong, purple, imprinted with 167

Methenamine Hippurate 1 g-RIS

oval, peach, imprinted with cor 139

Urex 1 g

oblong, white, imprinted with UR EX, VP

What are the possible side effects of methenamine (Hiprex)?

If you experience any of the following serious side effects, stop taking methenamine and seek emergency medical attention or contact your doctor immediately:

  • an allergic reaction (shortness of breath; closing of the throat; swelling of the lips, face, or tongue; or hives;
  • lower back or side pain;
  • blood in urine; or
  • increasingly painful or difficult urination.

Other, less serious side effects may be more likely to occur. Continue to take methenamine and talk to your doctor if you experience

  • nausea or upset stomach;
  • decreased appetite; or
  • skin rash.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects to FDA at 1-800-FDA-1088.

Read the Hiprex (methenamine hippurate) Side Effects Center for a complete guide to possible side effects

What is the most important information I should know about methenamine (Hiprex)?

Take all of the methenamine that has been prescribed for you even if you begin to feel better. Symptoms may start to improve before the infection is completely treated.

Take each dose with a full glass of water. Plenty of fluid should be consumed while taking methenamine.

Your healthcare provider may recommend drinking additional water and/or certain fruit juices (e.g., cranberry, plum, prune) and increased protein in the diet while taking methenamine to ensure adequate hydration and acidity of the urine. It may also be recommended to avoid citrus fruits and juices (e.g., orange, grapefruit, lemon), milk and dairy products, and antacids during treatment with methenamine. These products may decrease the effectiveness of methenamine. Follow your healthcare provider's instructions.

Side Effects Centers

Hiprex - User Reviews

Hiprex User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Hiprex sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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