Fosfomycin Overview

When working with Fosfomycin, a phosphonic‑acid antibiotic commonly prescribed for urinary tract infections. Also known as Monurol, it targets bacterial cell wall synthesis. This drug is part of a broad‑spectrum antibiotic class, making it useful against a range of gram‑negative and gram‑positive bugs. The primary condition it treats is urinary tract infection, an infection that affects the bladder, urethra, or kidneys. However, its effectiveness can be limited by bacterial resistance, which is rising in many regions. The drug Fosfomycin offers a single‑dose option that many patients find convenient.

How Fosfomycin Works and Typical Dosing

Fosfomycin blocks the enzyme MurA, halting the first step of peptidoglycan formation in bacterial cell walls. Because this step is unique, the drug works even when other antibiotics fail. For uncomplicated urinary tract infections in adults, the standard dose is a one‑time 3‑gram tablet taken with a full glass of water. Children and patients with reduced kidney function may need adjusted doses, usually calculated based on weight and creatinine clearance. The drug reaches peak urinary concentrations within 2–4 hours, staying above the minimum inhibitory concentration for up to 48 hours, which is why a single dose can clear many infections.

Side effects are generally mild. The most common complaints are gastrointestinal—nausea, diarrhea, or abdominal discomfort. Rarely, patients experience allergic reactions such as rash or itching. Because fosfomycin is excreted unchanged in the urine, it does not require liver metabolism, reducing the risk of drug‑drug interactions. Still, it’s wise to avoid concurrent use of nephrotoxic agents when possible, as the kidneys handle the clearance.

Resistance development is a key concern. Bacteria can acquire fosfomycin‑inactivating enzymes (FosA, FosB) or mutate transport proteins that bring the drug into the cell. Studies from 2022‑2024 show that resistance rates are still low for community‑acquired uropathogens, but they climb sharply in hospital‑associated strains, especially in patients with repeated antibiotic exposure. To preserve its usefulness, clinicians recommend confirming the pathogen’s sensitivity before prescribing fosfomycin for recurrent infections.

When compared with other first‑line agents like trimethoprim‑sulfamethoxazole or nitrofurantoin, fosfomycin shines for patients who cannot tolerate those drugs or have allergies. Unlike nitrofurantoin, which requires a 5‑day course, fosfomycin’s single‑dose regimen improves adherence. However, for complicated infections that extend beyond the lower urinary tract, longer‑acting agents such as fluoroquinolones may be necessary because fosfomycin’s urinary concentrations drop after 48 hours.

Special populations need extra attention. Pregnant women can use fosfomycin safely; it is classified as pregnancy category B in many regions. Children older than one month can receive weight‑based doses, but infants under one month are generally excluded due to limited safety data. Patients with severe renal impairment (eGFR <30 mL/min) should receive a reduced dose or consider an alternative antibiotic, as the drug’s clearance slows dramatically.

Below you’ll find a curated list of articles that dive deeper into fosfomycin’s clinical use, dosing nuances, side‑effect management, and resistance trends. Whether you’re a patient looking for practical tips or a clinician needing up‑to‑date guidance, the posts provide actionable insights you can apply right away.