MONUROL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MONUROL (MONUROL).
Fosfomycin inhibits bacterial cell wall synthesis by inactivating the enzyme UDP-N-acetylglucosamine-3-enolpyruvyltransferase (MurA), which catalyzes the first step of peptidoglycan biosynthesis.
| Metabolism | Fosfomycin is not significantly metabolized; it is eliminated unchanged primarily by renal excretion via glomerular filtration. |
| Excretion | Renal: 38% unchanged; fecal: 33% (via biliary), remainder as inactive metabolite (dihydrofosfomycin). |
| Half-life | Terminal elimination half-life: 5.7 hours (range 4-8 hours) in patients with normal renal function; prolonged to 9-15 hours in renal impairment (CrCl <80 mL/min); increases with age and renal disease. |
| Protein binding | Negligible: <1% bound to plasma proteins. |
| Volume of Distribution | Apparent Vd: 0.3-0.4 L/kg (approximately 20-30 L in adults); indicates distribution primarily into extracellular fluid; low tissue penetration except urinary tract. |
| Bioavailability | Oral (trometamol salt): approximately 34-41% (range 30-40%) under fasting conditions; increased by high-fat meal (up to 50-60% decrease, thus take on empty stomach). |
| Onset of Action | Oral (single dose 3 g): Clinical effect within 24-48 hours for uncomplicated UTI; peak plasma concentration at 2-2.5 hours. |
| Duration of Action | Urinary bactericidal concentrations persist for at least 36-48 hours after a single 3 g oral dose; sufficient for single-dose therapy in acute uncomplicated cystitis. |
3 g orally as a single dose (powder dissolved in water); for uncomplicated urinary tract infections.
| Dosage form | FOR SOLUTION |
| Renal impairment | Contraindicated if creatinine clearance <10 mL/min; dose adjustment not established for GFR 10-50 mL/min; use with caution. |
| Liver impairment | No dosage adjustment required for hepatic impairment; safety not established in severe liver disease. |
| Pediatric use | Children ≥5 years and ≥12 kg: 3 g orally as a single dose; children <5 years or <12 kg: not recommended. |
| Geriatric use | No specific dose adjustment; use same single 3 g dose; monitor renal function and consider potential decreased renal clearance. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MONUROL (MONUROL).
| Breastfeeding | Excreted in breast milk in small amounts. M/P ratio unknown. Considered compatible with breastfeeding; monitor infant for diarrhea or rash. |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; insufficient human data. Avoid first trimester due to potential risk; second and third trimester use only if clearly needed. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to fosfomycin or any component of the formulation"]
| Precautions | ["Hypersensitivity reactions including anaphylaxis and angioedema","Clostridioides difficile-associated diarrhea","Development of drug-resistant bacteria","Not for treatment of pyelonephritis or perinephric abscess"] |
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| Monitor renal function, hepatic enzymes, and complete blood count during prolonged therapy. Fetal ultrasound if used in pregnancy. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment. |