• Basic Info
• Top Questions
• Clinical Info
• Interactions

What happens if I overdose?

Seek emergency medical attention if an overdose is suspected.

Symptoms of a methenamine overdose are not known.

What should I avoid 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.

What are the possible side effects of methenamine?

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.

What other drugs will affect methenamine?

Do not take methenamine without first talking to your doctor if you are taking:

• a carbonic anhydrase inhibitor such as acetazolamide (Diamox), dichlorphenamide (Daranide), or methazolamide (Glauctabs, MZM, Neptazane);

• a sulfa product such as sulfadiazine, sulfamethoxazole (Bactrim, Septra, others), sulfasalazine (Azulfidine), and others;

• a diuretic (water pill); or

• a product that contains aluminum, calcium, magnesium, sodium bicarbonate, potassium or sodium citrate, or citric acid (such as antacids, vitamin or mineral pills, urinary alkalinizers, and other medications).

You may not be able to take methenamine, or you may require a dosage adjustment or special monitoring during treatment if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with methenamine. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including vitamins, minerals, and herbal products.

Where can I get more information?

Your pharmacist has additional information about methenamine written for health professionals that you may read.

What does my medication look like?

Methenamine is available with a prescription under the brand names Hiprex, Urex, and Mandelamine. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.