Maximum Dosing of Fosfomycin 3g Sachet for Uncomplicated UTI
For uncomplicated urinary tract infections in women, the maximum and recommended dose is a single 3-gram sachet of fosfomycin—this is a one-time dose, not to be repeated for the same episode of infection. 1
Standard Dosing Protocol
- The FDA-approved dosing for fosfomycin tromethamine is one sachet (3 grams) as a single dose for uncomplicated UTI (acute cystitis) in women 18 years and older 1
- This single-dose regimen provides therapeutic urinary concentrations for 24-48 hours, which is sufficient to inhibit most urinary tract pathogens 2, 3
- Multiple international guidelines, including the Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases, recommend fosfomycin as a single 3-gram oral dose 4, 2
Why Only One Dose?
- Following a single 3-gram dose, peak urinary concentrations occur within 4 hours and remain high (>128 mg/L) for 24-48 hours 3
- Clinical trials demonstrate bacteriological eradication rates of 75-90% at 5-11 days and 62-93% at 4-6 weeks after a single dose 3
- High clinical recovery rates (88.9%) and bacteriological eradication rates (94.9%) are achieved with single-dose therapy 5
Important Clinical Caveats
Fosfomycin is indicated ONLY for uncomplicated cystitis in women—it should not be used for:
When Single Dose May Be Insufficient
While the standard is one dose for uncomplicated UTI, research suggests that for complicated or recurrent infections (which are technically outside the FDA indication), some clinicians have used two 3-gram doses given 72 hours apart to maintain therapeutic urinary levels over 7 days 6. However, this multi-dose regimen is not FDA-approved and should not be used for standard uncomplicated UTI 1.