Phosphomycin Sachet Treatment for Uncomplicated UTI
A single dose of fosfomycin 3 g PO (one sachet) is the recommended treatment regimen for uncomplicated urinary tract infections. 1, 2
Administration Instructions
- The entire contents of the single-dose sachet should be dissolved in 3-4 ounces (1/2 cup) of cold or room temperature water (do not use hot water) 2
- Stir to dissolve completely before drinking 2
- Can be taken with or without food 2
- Should be consumed immediately after dissolving in water 2
Indications and Efficacy
Fosfomycin tromethamine is specifically indicated for:
- Uncomplicated urinary tract infections (acute cystitis) in women 2
- Effective against susceptible strains of Escherichia coli and Enterococcus faecalis 2
The single-dose regimen is particularly advantageous because:
- It provides high urinary concentrations that remain above the minimum inhibitory concentration (>128 mg/L) for 24-48 hours 3
- Bacteriological eradication rates of 75-90% are achieved 5-11 days after therapy 3
- Clinical cure rates of approximately 99% have been demonstrated in large clinical trials 3
- It has extremely low resistance rates (around 1-2%) compared to other antibiotics 4
Contraindications and Limitations
- Not indicated for pyelonephritis or perinephric abscess 2
- If bacteriuria persists or recurs after treatment, alternative antibiotics should be selected 2
Alternative Regimens
If fosfomycin is unavailable or contraindicated, guidelines recommend these alternatives for uncomplicated UTIs:
- Nitrofurantoin 100 mg PO every 6 hours 5, 1
- Trimethoprim-sulfamethoxazole (if local resistance patterns permit) 1
- Amoxicillin-clavulanate or cephalexin (in regions where appropriate) 1
Special Considerations
- While the standard regimen is a single 3g dose, some research suggests that for certain non-standard cases (not young women with uncomplicated UTI), a second 3g dose administered 72 hours after the first dose may be beneficial 6
- Fosfomycin has been shown to be comparable in efficacy to nitrofurantoin for uncomplicated UTI treatment, with similar clinical and microbiological cure rates 7
Common Pitfalls to Avoid
- Do not administer the powder without dissolving it in water first 2
- Do not use for complicated UTIs or pyelonephritis as it is only indicated for uncomplicated lower UTIs 2
- Do not rely on fosfomycin for persistent or recurrent infections; alternative antibiotics should be selected in these cases 2
- Ensure a urine culture is collected before starting antibiotics to confirm the diagnosis and susceptibility 1
Fosfomycin's single-dose regimen offers excellent patient compliance while maintaining high efficacy against common uropathogens, making it an ideal first-line option for uncomplicated UTIs in women.