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). |
| Molecular Weight | 54000 |
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 | UROBAK (urokinase) is contraindicated in first trimester due to risk of hemorrhage and potential teratogenic effects based on animal studies. |
| 2nd trimester | Use only if clearly needed and benefit outweighs risk. Monitor for bleeding complications. |
| 3rd trimester | Avoid near term due to increased risk of maternal hemorrhage and preterm labor. |
Clinical note
Comprehensive clinical and safety monograph for UROBAK (UROBAK).
| Placental transfer | Limited data; molecular weight >50,000 Da suggests minimal placental transfer, but animal studies show potential for crossing in small amounts. Clinical significance unknown. |
| Breastfeeding | UROBAK is a large protein molecule unlikely to be excreted into breast milk in significant amounts. However, due to limited human data, caution is advised. Use only if essential and monitor infant for adverse effects. |
■ FDA Black Box Warning
None.
| Serious Effects |
Active internal bleedingRecent (within 2 weeks) major surgery or traumaHistory of cerebrovascular accident (CVA) within 2 monthsIntracranial neoplasm or arteriovenous malformationSevere uncontrolled hypertensionKnown hypersensitivity to urokinase
| 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. |
| Food/Dietary | Take with food to maximize phosphate binding. Avoid high-phosphorus foods (dairy, nuts, beans, cola) but do not restrict intake; the drug binds phosphorus from food. Separate from oral antibiotics by at least 2 hours. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | UROBAK is not a recognized drug; no data available. |
| Fetal Monitoring | Not applicable due to lack of drug identification. |
| Fertility Effects | No information on reproductive impact. |
| Clinical Pearls | UROBAK (ferric citrate) is used for hyperphosphatemia in CKD. Monitor serum phosphate, calcium, and ferritin. Avoid co-administration with oral antibiotics; separate by at least 2 hours. May cause iron overload; check iron studies periodically. |
| Patient Advice | Take with meals to bind dietary phosphate. · Swallow tablets whole; do not crush or chew. · Do not take with antacids or calcium supplements at the same time. · Notify your doctor if you experience black, tarry stools or severe constipation. · Keep all lab appointments to monitor iron and phosphorus levels. |