You may want to consider this old stand-by now to cover drug-resistant bacteria.
This old drug is being used in new ways. It boasts single dose administration for certain indications and good coverage for multi-drug resistant bacteria.
It is FDA approved for un- complicated urinary tract infections (UTIs) in women as a single 3g oral dose. It is also used off-label for men and for complicated UTIs as three 3g doses, each 48-72 hours apart. Longer courses are used for prostatitis (3g every three days for 21 days) and for UTI prevention.
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A meta-analysis concluded that fosfomycin had comparable effectiveness to other first-line agents for uncomplicated UTIs . It is considered a first-line agent for uncomplicated UTIs in women by the Infectious Diseases Society of America (IDSA). Overall, we are seeing a revival of fosfomycin use.
How it Works
Fosfomycin is a small molecule, originally isolated from Streptomyces. It inhibits enzymes involved in bacterial cell wall synthesis and is bacteriocidal in both Gram positive and Gram negative bacteria, including many multi-drug resistant bacteria.
Discovered in Spain in 1969, production for medical use began there in 1971. It was initially used as the disodium salt form with parenteral administration for serious infections. It has not been as widely used as other drugs in more recent decades, though, so resistance is not widespread. This makes it useful in our era of diminishing antibiotic options. It is currently used mostly as fosfomycin-tromethamine, a water-soluble powder that is taken orally.
These are typically only mild, gastrointestinal symptoms, including diarrhea. For patients who are on longer courses, such as for recurrent UTI prophylaxis (one dose every 10 days for 6 months), super-infection with other fungi and bacteria can occur, including C. difficile diarrhea.
Pregnancy class B, generally considered safe. It is probably safe in breast-feeding mothers as the single dose form, though the manufacturer does not recommend it, so discarding expressed milk would be safest when feasible. The manufacturer recommends against using it for pyelonephritis 
No dose adjustment for older patients. No renal or hepatic dosing specified.
For uncomplicated UTIs, this is a single dose medication, which removes the possibility of medication non-compliance if the patient receives the dose in the ED.
Not all pharmacies carry fosfomycin in stock, and ordering it can take 24 hours or more. The cost is about $70-$90 per 3g dose depending on the pharmacy. Since there are inexpensive alternative agents for uncomplicated UTI, cost may preclude its use in some patients who are receiving prescriptions.
- Falagas et al. Fosfomycin versus other antibiotics for the treatment of cystitis: a meta-analysis of randomized controlled trials. J Antimicrob Chemother. 2010
- Gupta et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women. IDSA Guidlines. Clinical Practice Guidelines 2011
- Michalopoulos et al. The revival of fosfomycin Int J Infect Dis 2011