Severe. 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. November, 2005.
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.