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Methenamine/Sodium Acid Phosphate

    Brands

    DEA Class; Rx

    Common Brand Names; Uroquid-Acid No. 2, Utac

    • Antibiotics, Other

    Methenamine: Hydrolyzed in acidic urine to ammonia and formaldehyde, which are bactericidal agents; does not convert to formaldehyde in serum

    Sodium acid phosphate: Urinary acidifier; elicits osmotic effect in GI tract

    Use only after eradication of UTI by other appropriate antibiotic

    Methenamine: Indicated for prophylaxis/suppression for chronic recurring UTIs when long-term therapy is required

    Sodium salicylate: Analgesic

    Benzoic acid: Elicits weak antifungal and antibacterial properties; also helps acidify urine

    Methenamine

    • Hypersensitivity to methenamine or tartrazine (FD&C Yellow No. 5)
    • Renal or severe hepatic insufficiency
    • Concurrent sulfonamides or acetazolamide may form insoluble precipitate in urine

    Sodium acid phosphate

    • Hypersensitivity
    • Addison’s disease
    • Hyperphosphatemia
    • Acidification of urine in urinary stone disease
    • Urolithiasis or struvite stone formation
    • Severe renal impairment (ie, CrCl <30 mL/min)

    Dysuria

    Gastric upset

    Nausea

    Rash

    Diarrhea

    Nausea

    Stomach pain

    Vomiting

    Methenamine

    • Large doses may cause bladder irritation, urinary frequency, albuminuria, and hematuria
    • Maintain acidic pH of urine, especially when treating urea-splitting organisms (eg, Proteus, Pseudomonas)
    • Monitor LFTs, especially with history of liver impairment
    • Safe use not established during pregnancy, especially 1st and 2nd trimester
    • May precipitate uric acid stones in patients with gout

    Sodium acid phosphate

    • History of gastrointestinal pain
    • Sodium restriction
    • History of kidney stones
    • Risk of acute phosphate nephropathy

    Pregnancy Category: C

    Lactation: methenamine is excreted in human milk; caution advised, risk to infant cannot be ruled out

    Adults

    Initial: 2 tablets PO q6hr with liberal fluid intake

    Maintenance: 1-2 tablets PO q12hr

    Methenamine/sodium acid phosphate

    tablet

    • 500 mg/500 mg