Other antibacterials
ATC code: J01XX01 (Fosfomycin)
Brand names
Monurol, Fosfomicina Abamed, Fosfomicina Cinfa, Fosfomicina Stada
Phosphonic acid derivative, a bactericidal antibiotic with a unique mechanism. Inhibits the first step of bacterial cell wall synthesis via UDP-N-acetylglucosamine enolpyruvyl transferase (MurA). After a single 3 g oral dose (fosfomycin trometamol), it concentrates in urine, making it first-line for uncomplicated cystitis. In Spain, Monurol (Zambon) is the most-prescribed antibiotic for UTIs in primary care.
First line
First-line for uncomplicated acute cystitis in women per 2010 and Spanish SEMI 2022. Single 3 g oral dose of fosfomycin trometamol (Monurol) 2 hours before bedtime with an empty bladder. Covers E. coli (including some ESBL strains), Klebsiella, Proteus, Enterobacter. Efficacy 80-90%. Advantage over fluoroquinolones – lower resistance (E. coli to in Spain reaches 25-35%, to fosfomycin 2-5%).
The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.
Not recommended
Fosfomycin tromethamine is prescribed as a broad-spectrum fallback in respiratory viral infections. 2024 AWaRe and 2024 confine fosfomycin to uncomplicated UTIs and outpatient bacteriuria prophylaxis in pregnancy. Use in upper respiratory infections, bronchitis or pneumonia is not indicated: oral fosfomycin achieves meaningful concentrations only in urine.
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Drug of choice for uncomplicated UTI and asymptomatic bacteriuria in pregnancy. FDA category B. Acceptable in all trimesters as a single 3 g dose.
Minimal milk excretion. Single dose during breastfeeding is safe.
Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.
Fosfomycin is evaluated for the following indications with varying evidence strength: Uncomplicated acute cystitis in women (evidence tier A), Acute viral upper respiratory infection (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of Fosfomycin (≥ 1 in 100): Diarrhea, Nausea, Headache, Vaginitis, Rash. See the Safety section for uncommon and serious reactions.
FDA category B. Drug of choice for uncomplicated UTI and asymptomatic bacteriuria in pregnancy. FDA category B. Acceptable in all trimesters as a single 3 g dose.
Minimal milk excretion. Single dose during breastfeeding is safe.
Fosfomycin is contraindicated in: Fosfomycin hypersensitivity; Severe renal impairment (eGFR below 10 mL/min); Age under 12 (for Monurol formulation). Full list in the Safety section.