Fosfomycin Dosing for Uncomplicated UTI
For uncomplicated cystitis in women, administer a single 3-gram oral dose of fosfomycin tromethamine, which is the FDA-approved regimen and provides therapeutic urinary concentrations for 24-48 hours. 1, 2
Standard Dosing Regimen
The recommended dose is one 3-gram sachet of fosfomycin tromethamine granules mixed with water, taken as a single dose for women 18 years and older with uncomplicated UTI (acute cystitis). 2
This single-dose regimen is specifically recommended by the European Association of Urology and the American Urological Association as a first-line therapy option (Grade B evidence). 1
The medication may be taken with or without food, but must always be mixed with water before ingesting—never take in dry form. 2
Duration and Follow-Up
Duration is a single dose only for uncomplicated cystitis—no repeat dosing is needed for standard uncomplicated UTI. 1, 2
The single dose provides therapeutic urinary concentrations for 24-48 hours, with some studies showing activity for up to 2-4 days. 1, 3
Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients. 1
If symptoms do not resolve by the end of treatment or recur within 2 weeks, obtain urine culture and antimicrobial susceptibility testing. 1
Important Clinical Limitations
Fosfomycin is FDA-approved and guideline-recommended ONLY for uncomplicated cystitis in women—it should not be used for pyelonephritis, complicated UTIs, or routinely in men due to insufficient efficacy data. 1, 4
The European Association of Urology explicitly does not recommend fosfomycin for routine use in men with UTIs due to limited clinical efficacy data in this population. 4
For complicated UTIs with systemic symptoms (including male UTIs), guidelines recommend combination therapy with beta-lactam/aminoglycoside combinations or third-generation cephalosporins for 7-14 days. 4
Special Populations
Pregnancy: Fosfomycin is safe in pregnancy and recommended by European Urology guidelines for asymptomatic bacteriuria in pregnant women as standard short-course treatment or single-dose administration. 1, 3
For multidrug-resistant pathogens (ESBL-producing organisms, VRE, MRSA) causing uncomplicated UTI, the same single 3-gram oral dose is recommended. 1
Common Pitfall to Avoid
Do not use multi-dose regimens (3 grams every 48-72 hours for 3 doses) for uncomplicated UTI—this regimen has been studied for complicated lower UTI in patients who failed other therapies or have MDR pathogens 5, 6, but the FDA-approved and guideline-recommended regimen for uncomplicated UTI remains a single dose only. 1, 2
Adverse Effects
The most commonly reported adverse events are diarrhea, nausea, and vomiting, occurring in approximately 4-6% of patients. 1, 5
Gastrointestinal disturbances and skin rash may occur but are generally mild. 1
Fosfomycin has minimal propensity for collateral damage to intestinal flora compared to other antibiotics. 1