Fosfomycin is a broad-spectrum, bactericidal antibiotic derived from phosphonic acid. It is chemically distinct from other antibiotic classes and is primarily used for the treatment of uncomplicated lower urinary tract infections (UTIs), particularly acute cystitis. In India, it is widely prescribed as a single-dose therapy, offering high efficacy against common uropathogens like Escherichia coli and Enterococcus faecalis. Its unique mechanism of action and low resistance profile make it a valuable first-line agent in the Indian clinical setting.
Adult: For uncomplicated cystitis: Fosfomycin Tromethamine 3g single oral dose (one sachet).
Note: Take on an empty stomach (at least 2-3 hours before or after a meal) for optimal absorption. Dissolve the entire content of one 3g sachet in 90-120 mL (half a glass) of plain, cool water. Stir and drink immediately. Do not use hot water. Do not take with antacids containing magnesium or aluminum, as they can bind fosfomycin and reduce absorption.
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 biosynthesis of peptidoglycan, a critical component of the bacterial cell wall.
Pregnancy: Category B: Animal studies show no risk, but adequate human studies are lacking. Used clinically for UTIs in pregnancy when benefits outweigh risks. Considered safe, especially as a single dose. Consult obstetrician.
Driving: May cause dizziness. Patients should assess their individual response before driving or operating machinery.
| Metoclopramide | Decreases serum concentration and urinary excretion of fosfomycin, reducing efficacy. | Major |
| Magnesium/Aluminum Antacids | Cationic binding reduces oral absorption of fosfomycin. | Major |
| Calcium supplements | May impair absorption. Separate administration by at least 2 hours. | Moderate |
| Cimetidine | May reduce renal excretion of fosfomycin, increasing plasma levels. | Moderate |
| Other Antibiotics (e.g., Aminoglycosides, Beta-lactams) | Synergistic bactericidal effect in vitro against some pathogens. | Minor (Beneficial) |