Fosfomycin

Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026

Fosfomycin is a broad-spectrum bactericidal antibiotic most commonly used as a single oral 3 g dose (as fosfomycin tromethamine) to treat uncomplicated urinary tract infections (acute cystitis) in women. It retains activity against many multidrug-resistant uropathogens, including extended-spectrum beta-lactamase (ESBL) producing Escherichia coli, because of its distinct mechanism and limited cross-resistance. Its convenient single-dose regimen supports adherence, though it is not appropriate for pyelonephritis or other complicated upper-tract or systemic infections in its oral form.

Exploratory record, not a reviewed medical publication.

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In short

What the research says.

A quick, data-only summary. The full evidence, dosing, and sources are below.

Fosfomycin is a broad-spectrum bactericidal antibiotic most commonly used as a single oral 3 g dose (as fosfomycin tromethamine) to treat uncomplicated urinary tract infections (acute cystitis) in women. NutriStack rates the supporting evidence as strong. Common adult dosing is Adults (women): single 3 g oral sachet of fosfomycin tromethamine dissolved in water, taken once. Some guidelines use repeat dosing (e.g., 3 g every 48-72 hours for 2-3 doses) for complicated lower UTI or in men, off-label., though a prescriber sets the actual dose. This profile indexes 3 sources.

What it's good for

Treatment of uncomplicated urinary tract infections (acute cystitis) in women^3,2
Effective single-dose option against many multidrug-resistant uropathogens including ESBL-producing E. coli^1,3
Convenient one-dose regimen that supports adherence^1,3

What to watch for

Diarrhea
Nausea
Headache
Known hypersensitivity to fosfomycin^1,2
Not indicated for pyelonephritis or perinephric abscess; oral form is inadequate for complicated upper-tract or systemic infection^1,3

The bottom line

Evidence rating strong. Most-documented uses: treatment of uncomplicated urinary tract infections (acute cystitis) in women, effective single-dose option against many multidrug-resistant uropathogens including esbl-producing e. coli, convenient one-dose regimen that supports adherence. 3 sources indexed (2008–2017), with 0 interaction records on file.

The science

How it works, mechanistically.

Core mechanism

Fosfomycin is a phosphoenolpyruvate analog that irreversibly inhibits MurA (UDP-N-acetylglucosamine enolpyruvyl transferase), the enzyme catalyzing the first committed step of bacterial peptidoglycan (cell wall) biosynthesis. By covalently binding a cysteine residue in the MurA active site, it blocks the conversion of UDP-N-acetylglucosamine to UDP-N-acetylglucosamine enolpyruvate, halting murein assembly and producing bactericidal cell lysis. The drug enters bacterial cells via the glycerophosphate (GlpT) and hexose phosphate (UhpT) transport systems, and it concentrates in the urine, where high levels support its efficacy in lower urinary tract infections.^2,1

Class

Phosphonic acid antibacterial

Absorption

Best on an empty stomach

Dosing

Dosing & protocol.

Common range

Adults (women): single 3 g oral sachet of fosfomycin tromethamine dissolved in water, taken once. Some guidelines use repeat dosing (e.g., 3 g every 48-72 hours for 2-3 doses) for complicated lower UTI or in men, off-label.

Recommended form

Oral granules (3 g sachet) dissolved in 90-120 mL (3-4 oz) of cool water and taken immediately

Oral bioavailability of fosfomycin tromethamine is roughly 30-40 percent and is reduced by food, so it is best taken on an empty stomach (about 2-3 hours before or after a meal). Dissolve the granules in cool water, not hot, and drink immediately. It is renally excreted largely unchanged, concentrating in the urine.^1,3

Safety

Full safety detail.

Side effects

Diarrhea
Nausea
Headache
Vaginitis
Dizziness
Abdominal pain
Dyspepsia
Rarely Clostridioides difficile-associated diarrhea and colitis
Rare hypersensitivity reactions including angioedema and anaphylaxis

Contraindications

Known hypersensitivity to fosfomycin^1,2
Not indicated for pyelonephritis or perinephric abscess; oral form is inadequate for complicated upper-tract or systemic infection^1,3
Use with caution in severe renal impairment (reduced urinary concentration limits efficacy)

Sources

Sources, by evidence tier.

Numbered references. Citations throughout the page link here.

Reviews & position papers

1International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in WomenPMIDGupta K, Hooton TM, Naber KG, et al. · Clinical Infectious Diseases · 2011
IDSA/ESCMID guidelines list fosfomycin trometamol 3 g single dose as an appropriate first-line agent for acute uncomplicated cystitis owing to minimal resistance and low collateral damage.
2Fosfomycin: use beyond urinary tract and gastrointestinal infectionsPMIDFalagas ME, Giannopoulou KP, Kokolakis GN, Rafailidis PI · Clinical Infectious Diseases · 2008
Fosfomycin acts as a phosphoenolpyruvate analog that irreversibly inhibits MurA (enolpyruvyl transferase), blocking the initial step of bacterial cell wall biosynthesis and conferring activity with limited cross-resistance.

Reference material

3Monurol (fosfomycin tromethamine) US Prescribing InformationForest Pharmaceuticals (Allergan) · FDA Prescribing Information · 2017
Fosfomycin tromethamine 3 g as a single oral dose is approved for treatment of uncomplicated urinary tract infections (acute cystitis) caused by susceptible strains of E. coli and Enterococcus faecalis in women.

FAQ

Common questions.

Quick answers about Fosfomycin, drawn from the data on this page.

What is Fosfomycin?

What is Fosfomycin used for?

Commonly cited benefits of Fosfomycin include: Treatment of uncomplicated urinary tract infections (acute cystitis) in women; Effective single-dose option against many multidrug-resistant uropathogens including ESBL-producing E. coli; Convenient one-dose regimen that supports adherence. NutriStack rates the overall evidence as strong.

What is a typical dose of Fosfomycin?

A typical adult dose of Fosfomycin is Adults (women): single 3 g oral sachet of fosfomycin tromethamine dissolved in water, taken once. Some guidelines use repeat dosing (e.g., 3 g every 48-72 hours for 2-3 doses) for complicated lower UTI or in men, off-label.. The commonly recommended form is Oral granules (3 g sachet) dissolved in 90-120 mL (3-4 oz) of cool water and taken immediately. These are general ranges, not personalized advice; confirm the right dose with a clinician.

What are the side effects of Fosfomycin?

Reported side effects include diarrhea, nausea, headache, vaginitis, dizziness, abdominal pain. This is educational information; check with a healthcare professional before use.

How strong is the evidence for Fosfomycin?

NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.

Use this with your stack

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