Methenamine/Sulfonamides Interactions

This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

Medical warning:

Very Serious. These medicines may interact and cause very harmful effects and are usually not taken together. Contact your healthcare professional (e.g. doctor or pharmacist) for more information.

How the interaction occurs:

Methenamine is transformed into formaldehyde in the urine. Formaldehyde may cause your sulfonamide to form a precipitate (solid) in your urine.

What might happen:

A decrease in the effectiveness of your medicine may occur.

What you should do about this interaction:

Contact your healthcare professionals (e.g. doctor or pharmacist) about taking these two medicines together. They may already be aware of this drug interaction and may be monitoring you for it. Do not start, stop, or change the dosage of any medicine before checking with them first.

  • 1.Hiprex (methenamine hippurate) US prescribing information. Aventis Pharmaceuticals, Inc. December, 2017.
  • 2.Mandelamine (methenamine mandelate) US prescribing information. . Warner Chilcott, Inc. September, 2007.
  • 3.Urex (methenamine hippurate) Canadian prescribing information. Draxis Pharmaceuticals, Inc December, 2006.
  • 4.DICARLO FJ, MALAMENT SG, PHILLIPS GE. Formation of an insoluble condensation product from sulfamethizole and formaldehyde. J Pharm Sci 1963 Jan;52:104.

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CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgment of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.