Fosfomycin – Quick Guide to This One‑Dose Antibiotic

When working with Fosfomycin, a broad‑spectrum bactericidal antibiotic most often prescribed as a single oral dose for uncomplicated urinary tract infections. Also known as Monurol, it attacks bacterial cell walls by inhibiting the early step of peptidoglycan synthesis. Fosfomycin stands out because you can finish the whole course after one pill, which cuts down on missed doses and pharmacy trips. After swallowing the tablet, peak plasma levels appear within two hours, then the drug is excreted unchanged in the urine where it stays active for up to 48 hours. This prolonged urinary concentration is what makes a single dose sufficient for most uncomplicated cases. The medication is generally safe for adults, but clinicians avoid it in patients with severe kidney impairment (creatinine clearance <10 mL/min) because the drug can accumulate.

As soon as you hear the term urinary tract infection, an infection that affects the bladder, urethra or kidneys and causes burning, urgency and occasional fever, you start thinking about which drug will clear it fastest. Fosfomycin works well against many E. coli strains that cause cystitis, but rising antibiotic resistance, the ability of bacteria to survive drug exposure through genetic changes can limit its success. In such cases clinicians often compare it to other first‑line agents like nitrofurantoin, an oral antibiotic that concentrates in the urine and is effective for many lower urinary infections. Another factor to keep in mind is the local susceptibility profile. In some regions, more than 20 % of E. coli isolates show resistance to fosfomycin, prompting labs to recommend susceptibility testing before prescribing. If the test shows resistance, doctors may switch to nitrofurantoin, trimethoprim‑sulfamethoxazole or a fluoroquinolone, each with its own dosing schedule and side‑effect checklist. For women who experience recurrent infections, a rotating regimen that alternates fosfomycin with a different class can reduce the chance of resistance developing.

What’s Covered Below

Beyond uncomplicated cystitis, fosfomycin is also available in an intravenous form for complicated bacterial infections such as osteomyelitis or hospital‑acquired sepsis. This IV version reaches tissues that oral pills cannot, making it a useful tool when doctors face multi‑drug‑resistant organisms. The IV formulation, marketed under names like Zemdri, is given as a 2‑gram infusion every eight hours for serious infections. Studies have shown that combining IV fosfomycin with another agent such as meropenem can produce synergistic effects against carbapenem‑resistant Enterobacterales. However, the cost of IV therapy is higher and requires hospital stay or outpatient infusion services. For patients who are pregnant, oral fosfomycin is considered category B in many countries, meaning it’s generally regarded as safe, but you should still discuss it with your obstetrician. Because fosfomycin is off‑patent in many markets, numerous generic versions are available online. Shopping smart means checking for a licensed UK pharmacy, comparing the £5‑£10 price range, and confirming the product contains 3 g of the powder that reconstitutes to a 3‑gram dose. Avoid sites that offer “super‑cheap” pills without proper credentials – counterfeit products can lack the active ingredient and put you at risk. Take a look at the collection below for detailed side‑effect breakdowns, price‑saving guides, and step‑by‑step comparisons that let you choose the right fosfomycin regimen for your situation.