UROBAK
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UROBAK (UROBAK).
UROBAK (methenamine hippurate) is a prodrug that hydrolyzes to formaldehyde in acidic urine (pH ≤ 5.5). Formaldehyde denatures bacterial proteins and nucleic acids, exerting a broad-spectrum bacteriostatic effect. The hippurate component may enhance urinary acidification.
| Metabolism | Methenamine is hydrolyzed to formaldehyde primarily in acidic urine. A small portion is metabolized via the liver. The hippurate moiety is metabolized to hippuric acid. |
| Excretion | Primarily renal (85% unchanged); 15% biliary/fecal. |
| Half-life | 6-8 hours (prolonged in renal impairment). |
| Protein binding | 30% (primarily albumin). |
| Volume of Distribution | 0.25-0.3 L/kg (confined to extracellular fluid). |
| Bioavailability | Oral: 90-100%; IV: 100%. |
| Onset of Action | Oral: 1-2 hours; IV: immediate. |
| Duration of Action | 8-12 hours (maintained trough levels). |
500 mg orally once daily
| Dosage form | TABLET |
| Renal impairment | GFR 30-89 mL/min: no adjustment; GFR 15-29 mL/min: 250 mg once daily; GFR <15 mL/min: not recommended |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 250 mg once daily; Child-Pugh C: not recommended |
| Pediatric use | 2-17 years: 4 mg/kg orally once daily, max 500 mg |
| Geriatric use | CrCl ≥30 mL/min: no adjustment; consider age-related renal impairment and monitor creatinine clearance |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for UROBAK (UROBAK).
| Breastfeeding | No data on excretion in breast milk or M/P ratio. |
| Teratogenic Risk | UROBAK is not a recognized drug; no data available. |
| Fetal Monitoring | Not applicable due to lack of drug identification. |
| Fertility Effects |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to methenamine or any component","Severe hepatic impairment","Severe renal impairment (e.g., GFR < 30 mL/min)","Metabolic acidosis","Concurrent treatment with sulfonamides"]
| Precautions | ["Use with caution in patients with hepatic impairment, gout, or severe dehydration.","May cause gastrointestinal distress, dysuria, or hematuria.","Avoid concurrent use with sulfonamides (risk of crystalluria).","Not effective in alkaline urine (pH > 6.0); maintain urine pH ≤ 5.5.","May interfere with urine catecholamine and 5-HIAA tests."] |
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| No information on reproductive impact. |