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methenamine (Mandelamine, Hiprex, Urex)

Tradenames: Mandelamine, Hiprex, Urex. Indications: - used after erradication of bacterial infection to prevent or eliminate frequently occurring urinary tract infections [4] Contraindications: - avoid in patients with creatinine clearance < 40 mL/min Dosage: 1) mandelate: 1 g PO QID with meals & plently of water 2) hippurate: 1 g PO BID Tablet: as hippurate (Hiprex, Urex) 1 g Tablet: as mandelate (Mandelamine) 500 mg, 1 g. Antimicrobial activity: - E. coli - Enterococcus - Staphylococcus - Streptococcus pyogenes Most strains of Proteus, Pseudomonas & Enterobacter are resistant. Pharmacokinetics: 1) 10-20% metabolized by the liver 2) 1/2life is 3-6 hours 3) 90% eliminated in the urine 4) decreased effects are observed in patients with non-acidic urine Adverse effects: 1) not common (1-10%) - rash, nausea/vomiting, diarrhea, anorexia, abdominal cramping 2) uncommon (< 1%) - headache, elevated liver function tests, hematuria, bladder irritation, dysuria, crystalluria, gout Drug interactions: 1) sulfa drugs may precipitate in renal tubules when used in combination 2) milk, bicarbonate, acetazolamide inhibit hydrolysis of methenamine to bactericidal metabolites NH3 & formaldehyde by alkalinizing urine Mechanism of action: 1) mandelate lowers urinary pH 2) methenamine is hydrolyzed to ammonia plus formaldehyde in the distal renal tubule which are bactericidal [4]

Interactions

drug interactions

General

other antibiotic

Properties

MISC-INFO: elimination route KIDNEY LIVER pregnancy-category C safety in lactation +

Database Correlations

PUBCHEM correlations

References

  1. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  2. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  3. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  4. Harding C, Forbes R, Currer S et al. Alternative to prophylactic antibiotics for the treatment of recurrent urinary tract infections in women: Multicentre, open label, randomised, non-inferiority trial. BMJ 2022 Mar 9; 376:e068229. PMID: 35264408 Free article

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atropine/benzoic acid/hyoscyamine/methenamine/methylene blue/phenyl salicylate benzoate/hyoscyamine/methenamine/methylene blue/phenyl salicylate benzoic acid/hyoscyamine/methenamine/methylene blue/phenyl salicylate hyoscyamine/methenamine/methylene blue/phenyl salicylate hyoscyamine/methenamine/methylene blue/phenyl salicylate/salicylate/sodium phosphate hyoscyamine/methenamine/methylene blue/phenyl salicylate/sodium phosphate hyoscyamine/methenamine/methylene blue/salicylate hyoscyamine/methenamine/methylene blue/salicylate/sodium phosphate hyoscyamine/methenamine/methylene blue/sodium phosphate mandelic acid/methenamine/phosphate/sodium phosphate mandelic acid/methenamine/sodium phosphate methenamine/salicylate methenamine/sodium phosphate