Methenamine: Difference between revisions
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Latest revision as of 11:26, 24 August 2020
Background
- Indicated for the prevention of urinary tract infections
Mechanism of Action
- The prodrug is hydrolysed into formaldehyde and ammonia in acidic urine
Spectrum of Activity
- Active against essentially all bacteria and some fungi
- Urease-positive organisms such as Proteus can inhibit its action by alkalinizing the urine and preventing the production of formaldehyde
Indications
- Prophylaxis against urinary tract infection, especially in people without underlying urinary tract abnormalities
- Levels of formaldehyde achieved in urine probably aren't high enough to treat active infection
- No systemic antimicrobial activity
Dosing
- Methenamine mandelate 1 g po QID (max 6 g daily)
- Add urine acidifying drugs like ammonium chloride, ascorbic acid, or methionine if urine pH is greater than 5.5
- Methenamine hippurate 1 g PO bid
- Does not need urinary acidification
Adverse Drug Reactions
- Nausea, vomiting, diarrhea
- Pruritis and rash
- Urinary tract irritation from formaldehyde, including dysuria, albuminuria, and hematuria
- Gout flares
- Rare elevations in liver enzymes