What is the recommended treatment for uncomplicated urinary tract infections using Fosfomycin?

Fosfomycin for Uncomplicated Urinary Tract Infections

For uncomplicated cystitis in women, administer a single 3-gram oral dose of fosfomycin tromethamine, which is FDA-approved and recommended as first-line therapy by multiple international guidelines. 1

Standard Dosing and Administration

• The FDA-approved regimen is one sachet (3 grams) of fosfomycin tromethamine granules mixed with water, taken as a single dose for women 18 years and older with uncomplicated UTI (acute cystitis). 1
• The medication may be taken with or without food, but must never be ingested in dry form—always mix with water before administration. 1
• This single dose provides therapeutic urinary concentrations for 24-48 hours, which is sufficient to inhibit most urinary tract pathogens. 2

Guideline Support and Evidence Quality

• The American Urological Association recommends fosfomycin as one of three first-line therapies for uncomplicated UTIs with strong recommendation (Grade B evidence). 2
• The European Association of Urology similarly lists fosfomycin trometamol as a first-line treatment option for uncomplicated cystitis in women. 2
• While bacterial eradication rates may be somewhat lower than some other first-line agents, clinical efficacy is comparable, with the major advantage being single-dose convenience that improves adherence compared to 3-7 day regimens. 2

Specific Clinical Indications

Fosfomycin is indicated ONLY for uncomplicated cystitis in women—it should NOT be used for:

• Pyelonephritis or perinephric abscess 1
• Complicated UTIs (though off-label multi-dose regimens exist for this indication) 2
• Routine use in men (limited efficacy data in this population) 2

Special Populations

• Pregnant women with asymptomatic bacteriuria: Fosfomycin is safe in pregnancy and recommended as either standard short-course treatment or single-dose administration. 2
• VRE-related uncomplicated UTIs: The same single 3-gram oral dose is recommended for vancomycin-resistant Enterococcus causing uncomplicated UTIs. 3, 2

Antimicrobial Spectrum and Resistance

• Fosfomycin maintains excellent activity against multidrug-resistant pathogens including ESBL-producing organisms, VRE, and MRSA. 2
• The drug has minimal propensity for collateral damage to intestinal flora, resulting in minimal disruption to the gut microbiome. 2
• Clinical studies demonstrate maintained susceptibility of ESBL-producing E. coli to fosfomycin despite increased use. 4

Follow-Up and Treatment Failure

• Routine post-treatment urinalysis or urine cultures are NOT indicated for asymptomatic patients. 2
• If symptoms do not resolve by the end of treatment or recur within 2 weeks, perform urine culture and antimicrobial susceptibility testing. 2
• If persistence or reappearance of bacteriuria occurs after fosfomycin treatment, select other therapeutic agents. 1

Adverse Effects

• The most commonly reported adverse events are diarrhea, nausea, and vomiting, which are generally transient, mild, and self-limiting. 2, 5
• Gastrointestinal disturbances and skin rash may occur but are generally mild. 2
• The incidence of adverse events is low overall, with only 2% experiencing mild adverse effects in clinical practice. 4

Critical Pitfalls to Avoid

Do not use fosfomycin for upper urinary tract infections: Fluoroquinolones and cephalosporins are preferred for oral treatment of pyelonephritis. 2 The FDA label explicitly states fosfomycin is not indicated for pyelonephritis or perinephric abscess. 1

Do not prescribe for men with UTIs: Clinical efficacy data is limited in male populations, and guidelines do not recommend routine use in this group. 2

Do not use for asymptomatic bacteriuria except in pregnant women and before urological procedures breaching the mucosa. 2