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METHENAMINE degrades in an acidic urine environment releasing formaldehyde which provides bactericidal or bacteriostatic action. It is well absorbed from the gastrointestinal tract. 70 to 90% reaches the urine unchanged at which point it is hydrolyzed if the urine is acidic.Within 24 hours it is almost completely (90%) excreted; of this amount at pH 5, approximately 20% is formaldehyde. Protein binding - some formaldehyde is bound to substances in the urine and surrounding tissues. Methenamine is freely distributed to body tissue and fluids but is not clinically significant as it does not hydrolyze at a pH greater than 6.8.
PHENYL SALICYLATE releases salicylate, a mild analgesic for pain.
METHYLENE BLUE possesses weak antiseptic properties. It is well absorbed by the gastrointestinal tract and is rapidly reduced to leukomethylene blue which is stabilized in some combination form in the urine. 75% is excreted unchanged.
BENZOIC ACID has a mild antibacterial and antifungal action. It also helps maintain an acid pH in the urine necessary for the degradation of methenamine.
HYOSCYAMINE SULFATE is a parasympatholytic drug which relaxes smooth muscles. Protein binding for hyoscyamine sulfate is moderate. Biotransformation for hyoscyamine sulfate is hepatic. It is well absorbed from the gastrointestinal tract. The majority of hyoscyamine sulfate is excreted unchanged.
Last reviewed on RxList: 8/8/2008
This monograph has been modified to include the generic and brand name in many instances.
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