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Methenamine

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Methenamine, Methenamine Hippurate, Methenamine Mandelate

  • See Also
  1. Recurrent Cystitis
  • Indications
  1. Recurrent Cystitis
    1. Short term prophylaxis in patients without renal tract abnormalities
  • Mechanism
  1. Metabolized to formaldehyde in the urine, killing local Microbes
  • Dosing
  1. Methenamine Hippurate (preferred)
    1. Adult: 1 g orally twice daily
    2. Child age 6-12 years: 500 mg orally twice daily
  2. Methenamine Mandelate
    1. Older preparation with less evidence (released before 1938 FDA reviews started)
    2. Adult: 1 g orally four times daily
    3. Child age 6-12 years: 500 mg orally four times daily
    4. Child age <6 years: 250 mg orally four times daily
  • Drug Interactions
  1. Trimethoprim Sulfamethoxazole (TMP-SMZ)
    1. Formaldehyde (Methenamine metabolite) reacts with Sulfonamides, forming precipitates
    2. Results in Crystalluria
  • Resources
  1. Methenamine Hippurate (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9f002ad9-58e7-44f2-a980-3cc3f36bbd9b
  2. Methenamine Mandelate (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cc299e8a-cf9a-4dc6-b6e6-972141e59296
  • References
  1. (2026) Presc Ins 33(6): 1-3
  2. Weidner (2018) Email communication, received 9/1/2018
  3. Lee (2012) Cochrane Database Syst Rev (10): CD003265 +PMID: 23076896 [PubMed]