Methenamine Dosage

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Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for Cystitis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Adult Dose for Cystitis Prophylaxis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Adult Dose for Pyelonephritis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Adult Dose for Urinary Tract Infection

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Pediatric Dose for Cystitis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections:
6 to 12 years: 0.5 to 1 g orally twice a day (morning and night)
13 years or older: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections:
6 to 12 years: 0.5 g orally 4 times a day (after each meal and at bedtime)
13 years or older: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Pediatric Dose for Cystitis Prophylaxis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections:
6 to 12 years: 0.5 to 1 g orally twice a day (morning and night)
13 years or older: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections:
6 to 12 years: 0.5 g orally 4 times a day (after each meal and at bedtime)
13 years or older: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Pediatric Dose for Pyelonephritis

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections:
6 to 12 years: 0.5 to 1 g orally twice a day (morning and night)
13 years or older: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections:
6 to 12 years: 0.5 g orally 4 times a day (after each meal and at bedtime)
13 years or older: 1 g orally 4 times a day (after each meal and at bedtime)

Usual Pediatric Dose for Urinary Tract Infection

Hippurate:
Prophylactic or suppressive treatment of frequently recurring urinary tract infections:
6 to 12 years: 0.5 to 1 g orally twice a day (morning and night)
13 years or older: 1 g orally twice a day (morning and night)

Mandelate:
Suppression or elimination of bacteriuria associated with pyelonephritis, cystitis, and other chronic urinary tract infections:
6 to 12 years: 0.5 g orally 4 times a day (after each meal and at bedtime)
13 years or older: 1 g orally 4 times a day (after each meal and at bedtime)

Renal Dose Adjustments

Contraindicated in patients with renal insufficiency

Liver Dose Adjustments

Contraindicated in patients with severe hepatic insufficiency

Precautions

Methenamine is contraindicated in patients with severe dehydration.

Methenamine is contraindicated in patients taking sulfonamides as some sulfonamides may form an insoluble precipitate with formaldehyde in the urine.

Methenamine hippurate should be used only after eradication of the infection by other appropriate antimicrobials.

Methenamine should not be used alone in the treatment of acute parenchymal infections causing systemic symptoms.

Periodic liver function tests are recommended with methenamine hippurate, especially in patients with hepatic impairment.

Methenamine mandelate should be avoided in patients with gout as it may precipitate urate crystals in their urine. This may also occur in patients with predisposition to uric acid stone formation.

Dysuria may occur (usually at higher than recommended dosage). This can be controlled by reducing the dosage and the acidification. Methenamine mandelate is not recommended when urine acidification is contraindicated or unattainable.

The efficacy of therapy should be monitored by repeated urine cultures. Urinary pH should be monitored to assure an acid pH of the urine is maintained. Supplemental acidification of the urine may be recommended depending on urinary pH and clinical response.

Safety and effectiveness have not been established in pediatric patients less than 6 years of age.

Dialysis

Contraindicated in patients with renal insufficiency

Other Comments

Since antibacterial activity of methenamine is greater in acid urine (maximum efficacy occurs at pH 5.5 or less), alkalinizing foods and medications should be restricted.

Methenamine is generally not used for treatment of active urinary tract infections.

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