Fosfomycin is a broad-spectrum, bactericidal antibiotic derived from phosphonic acid. The 4gm single-dose sachet formulation (fosfomycin trometamol) is specifically indicated for the treatment of uncomplicated lower urinary tract infections (acute cystitis) in women. It works by inhibiting the early stage of bacterial cell wall synthesis. In the Indian context, it is a valuable first-line agent due to its high efficacy against common uropathogens, including some multidrug-resistant strains, and its convenient single-dose regimen which improves patient compliance.
Adult: One single 4gm sachet (as fosfomycin trometamol) dissolved in a glass of water (approx. 90-120 mL) for acute uncomplicated cystitis. A second dose may be considered after 48-72 hours in some cases, but single-dose is standard.
Note: Administer on an empty stomach (at least 2-3 hours before or after a meal) for optimal absorption. Empty the entire contents of one sachet into a glass containing 90-120 mL of plain, cool water. Stir to dissolve completely. Drink the entire solution immediately. Do not use hot water. The sachet is for single use only.
Fosfomycin is a phosphoenolpyruvate (PEP) analog. It irreversibly inhibits the enzyme UDP-N-acetylglucosamine enolpyruvyl transferase (MurA). This enzyme catalyzes the first committed step in the cytoplasmic phase of bacterial cell wall (peptidoglycan) biosynthesis. Inhibition of MurA prevents the formation of N-acetylmuramic acid, a crucial peptidoglycan precursor.
Pregnancy: Category B: Animal studies show no risk, but no adequate, well-controlled studies in pregnant women. Used clinically for asymptomatic bacteriuria in pregnancy. Should be used only if clearly needed, under medical supervision.
Driving: Dizziness has been reported. Patients should be cautioned about operating machinery or driving if they experience dizziness.
| Metoclopramide | Reduces serum concentration and urinary excretion of fosfomycin by accelerating GI transit. Avoid concomitant use. | Major |
| Cimetidine | May reduce urinary excretion of fosfomycin, potentially altering efficacy. Monitor. | Moderate |
| Other antibiotics (e.g., Aminoglycosides, Beta-lactams) | Synergistic or additive antibacterial effect against some pathogens. No significant PK interaction. | Minor |
| Drugs that prolong QT interval (e.g., Erythromycin, Fluoroquinolones, Antipsychotics) | Theoretical additive risk of QT prolongation. Use with caution. | Moderate |