Methenamine mandelate clinical pharmacology

Methenamine mandelate
METHENAMINE MANDELATE® FDA Package Insert
Description
Clinical Pharmacology
Indications and Usage
Contraindications
Warnings and Precautions
Adverse Reactions
Dosage and Administration
How Supplied
Labels and Packages

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohamed Moubarak, M.D. [2]

Clinical Pharmacology

Methenamine mandelate, USP is readily absorbed but remains essentially inactive until it is excreted by the kidney and concentrated in the urine. An acid urine is essential for antibacterial action, with maximum efficacy occurring at pH 5.5 or less. In an acid urine, mandelic acid exerts its antibacterial action and also contributes to the acidification of the urine. Mandelic acid is excreted both by glomerular filtration and tubular excretion. The methenamine component, in an acid urine, is hydrolyzed to ammonia and to the bactericidal agent formaldehyde. There is equally effective antibacterial activity against both gram-positive and gram-negative organisms, since the antibacterial action of mandelic acid and formaldehyde is nonspecific. There are reports that methenamine mandelate, USP is ineffective in some infections with Proteus vulgaris and urea-splitting strains of Pseudomonas aeruginosa and A aerogenes. Since urea-splitting strains may raise the pH of the urine, particular attention to supplementary acidification is required. However, results in any single case will depend to a large extent on the underlying pathology and the overall management.

References

Adapted from the FDA Package Insert.