What is Monurol (fosfomycin) used to treat?

What is Monurol (Fosfomycin) Used to Treat?

Monurol (fosfomycin tromethamine) is FDA-approved exclusively for treating uncomplicated urinary tract infections (acute cystitis) in women caused by susceptible strains of Escherichia coli and Enterococcus faecalis. 1

Primary Indication: Uncomplicated Cystitis in Women

• The FDA label explicitly restricts Monurol to uncomplicated lower urinary tract infections (acute cystitis) in women only. 1
• The standard dose is a single 3-gram oral dose, which provides therapeutic urinary concentrations for 24-48 hours. 2
• Multiple international guidelines (European Association of Urology, American Urological Association) recommend fosfomycin as a first-line treatment option for uncomplicated cystitis in women, with comparable clinical efficacy to nitrofurantoin and ciprofloxacin but with the advantage of single-dose administration. 2

What Monurol is NOT Approved For

Critical limitations to understand:

• Pyelonephritis (kidney infection): The FDA label explicitly states fosfomycin is NOT indicated for pyelonephritis or perinephric abscess. 1 The European Association of Urology reinforces this, stating fosfomycin should not be used for pyelonephritis or complicated UTIs due to insufficient efficacy data. 2, 3
• Complicated UTIs: Not recommended for any complicated urinary tract infection. 2
• Men with UTIs: The European Urology guidelines do not recommend fosfomycin for routine use in men with UTIs due to limited clinical efficacy data in this population. 2
• Urosepsis: Fosfomycin is explicitly not recommended for urosepsis or any septic presentation—guidelines restrict it to uncomplicated lower UTI without systemic involvement. 3

Special Population: Pregnant Women

• Fosfomycin is safe in pregnancy and is recommended by European Urology guidelines for asymptomatic bacteriuria in pregnant women using either standard short-course treatment or single-dose administration. 2
• Single-dose fosfomycin had similar bacteriological efficacy to 5-7 day courses of cefuroxime or amoxicillin/clavulanic acid in pregnant women with asymptomatic bacteriuria or lower UTI. 4

Activity Against Resistant Organisms

• Fosfomycin has activity against multidrug-resistant pathogens including ESBL-producing E. coli, vancomycin-resistant Enterococcus (VRE), and MRSA in the urinary tract. 2
• For VRE causing uncomplicated UTIs, the same single 3-gram oral dose is recommended. 2
• However, this activity is only clinically relevant for uncomplicated cystitis—do not extrapolate to systemic or complicated infections. 2, 1

Common Pitfalls to Avoid

1. Do not prescribe Monurol for pyelonephritis symptoms (fever, flank pain, systemic symptoms)—use fluoroquinolones or cephalosporins instead. 2, 3
2. Do not use for recurrent UTIs requiring suppressive therapy—if bacteriuria persists or reappears after fosfomycin treatment, select other therapeutic agents. 1
3. Do not use for complicated UTIs (structural abnormalities, catheters, immunosuppression)—intravenous antibiotics are required. 2
4. Do not use for men unless no other options exist and only for uncomplicated cystitis, as efficacy data is limited. 2

Adverse Effects

• The most commonly reported adverse events are gastrointestinal: diarrhea, nausea, and vomiting. 2
• These effects are generally mild and self-limited. 2
• Fosfomycin has minimal collateral damage to intestinal flora compared to other antibiotics, preserving the gut microbiome. 2

Administration Details

• Fosfomycin can be taken without regard to food, though high-fat meals delay the rate (but not extent) of urinary excretion. 1
• Approximately 38% of the dose is recovered unchanged in urine, achieving mean urinary concentrations of 706 mcg/mL within 2-4 hours under fasting conditions. 1
• Urinary concentrations ≥100 mcg/mL are maintained for approximately 26 hours. 1

Off-Label Intravenous Use (Not Monurol Brand)

• Intravenous fosfomycin (fosfomycin disodium, not the oral Monurol formulation) is used off-label in combination therapy for carbapenem-resistant Gram-negative infections, but this is a different formulation and indication entirely. 5, 6
• Oral fosfomycin has <50% bioavailability, making it unsuitable for systemic infections. 7