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methenamine/sodium salicylate/benzoic acid (OTC)Brand and Other Names:Cystex

 
 
 

Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

methenamine/sodium salicylate/benzoic acid

tablet

  • 162mg/162.5mg/32mg
more...

Urinary Tract Infection Prophylaxis

2 tablets PO q12hr

Administer with meals and at bedtime

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

Dosage Forms & Strengths

methenamine/sodium salicylate/benzoic acid

tablet

  • 162mg/162.5mg/32mg
more...

Urinary Tract Infection Prophylaxis

<16 years: Safety/efficacy not established

>16 years: 2 tablets PO q6hr

Administer with meals and at bedtime

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

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Adverse Effects

1-10%

Methenamine

  • Dysuria
  • Gastric upset
  • Nausea
  • Rash

Frequency Not Defined

Sodium salicylate

  • Angioedema
  • Bronchospasm
  • CNS alteration
  • Dermatologic problems
  • GI pain/ulceration/bleeding
  • Hepatotoxicity
  • Hearing loss
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Warnings

Contraindications

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 Salicylate

  • Hypersensitivity to aspirin or NSAIDs
  • Bleeding gastrointestinal ulcers
  • Asthma, Nasal polyps associated with asthma
  • Hemolytic anemia from PK & G6PD deficiency
  • Hemophilia
  • Hemorrhagic diathesis
  • Hemorrhoids, Lactating women, Sarcoidosis, Thrombocytopenia, Ulcerative colitis

Cautions

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 Salicylate

  • Anemia
  • GI malabsorption
  • History of peptic ulcers
  • Gout
  • Hepatic disease
  • Hypochlorhydria, Hypoprothrombinemia, Renal impairment, Renal calculi, Thyrotoxicosis, Vitamin K deficiency
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Pregnancy & Lactation

Pregnancy Category: C

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

Pregnancy Categories

A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA:Information not available.

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Pharmacology

Methenamine

Half-Life: 3-6 hr

Absorption: well absorbed; 10-30% hydrolyzed by gastric acid unless enteric coated tablet

Peak Urine Time: (formaldehyde) 2 hr for hippurate salt, 3-8 hr for mandelate salt

Metabolism: by liver (10-25%)

Excretion: urine (90%)

Mechanism of Action

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

Sodium salicylate: Analgesic

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

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