Urinary Tract Infections
Methenamine hippurate or methenamine mandelate is used for prophylaxis or suppression of recurrent urinary tract infections (bacteriuria), especially when long-term therapy is considered necessary.
Methenamine hippurate or methenamine mandelate should be used only after the urinary tract infection has been eradicated by other appropriate anti-infectives. Methenamine is not effective in systemic bacterial infections and has no effect on bacteria in blood or tissues outside the urinary tract. Methenamine hippurate and methenamine mandelate should not be used alone in the treatment of acute parenchymal infections causing systemic symptoms (e.g., chills, fever).
Efficacy of methenamine therapy should be monitored by periodic urine cultures. Antibacterial effects of methenamine are maximal when urine pH is 5.5 or less. Urinary pH should be monitored during methenamine therapy and supplementary acidification used, if required. Supplementary acidification may be achieved by dietary regulation and/or concomitant administration of acidifying agents (e.g., ammonium chloride, ascorbic acid, methionine). This is particularly important when the causative organisms are urea-splitting strains of Proteus or Pseudomonas which increase urinary pH.