Internal Medicine Residents’ Perceptions of Fosfomycin use – a Brief Report
Abstract
Background: Fosfomycin is approved by the FDA for treating uncomplicated cystitis caused by Escherichia coli and Enterococcus faecalis. However, it is often prescribed off-label for broader indications, with limited data on physician knowledge and practice patterns.
Methods: We surveyed residents in the Yale New Haven Internal Medicine Residency program across three teaching hospitals to assess awareness, prescribing habits, and perceived indications for fosfomycin.
Results: Seventy-eight residents responded (58% response rate); 89.7% were familiar with fosfomycin, and 71.4% had prescribed it. The most common indication was uncomplicated cystitis (94.3%), followed by pyelonephritis (41.4%) and prostatitis (32.9%). E. coli (71.4%) and Klebsiella pneumoniae (68.6%) were the most frequently selected organisms. Only 30% correctly identified uncomplicated cystitis as the sole FDA-approved indication, and no responses fully aligned with the approved spectrum of use.
Conclusion: Internal medicine trainees demonstrated significant gaps in knowledge regarding fosfomycin’s approved role. Educational efforts are needed to promote judicious prescribing and preserve its effectiveness against multidrug-resistant pathogens
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Introduction
Fosfomycin, discovered in the 1960s, is a synthetic, broad-spectrum, bactericidal antibiotic which works by inhibiting the enzyme MurA, an essential for bacterial cell wall synthesis [1]. Fosfomycin is available as an oral suspension in the United States, and the pharmacokinetics allow for one-time dosing [2], making it a good oral option, especially in the outpatient setting for treating urinary tract infections (UTI). Fosfomycin is approved by the U.S. Food and Drug Administration (FDA) to treat uncomplicated cystitis caused by Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) in women [2].
We noticed that non-infectious disease specialists prescribe fosfomycin to treat various conditions outside of its FDA approved indications, including complicated cystitis, pyelonephritis, long-term UTI prophylaxis, and prostatitis. In addition, it was also used to target many other organisms such as Klebsiella pneumoniae, Proteus mirabilis, Enterobacter cloacae complex, Pseudomonas aeruginosa, etc. Despite a few anecdotal successful cases, no extensive data is available for off-label uses, which begs the question of the nescience surrounding the usage of fosfomycin. This analysis aimed to assess the understanding of fosfomycin use among internal medicine trainees at a tertiary academic institution.
Conclusion
This study highlights notable gaps in knowledge regarding fosfomycin use among internal medicine residents, particularly in relation to its limited FDA-approved indication and lack of established efficacy for non-urinary tract infections or Grampositive organisms. The frequent selection of off-label uses, including pyelonephritis, bacteremia, and broad Gram-negative or Gram-positive coverage, underscores the risk of inappropriate prescribing. Given the increasing prevalence of multidrugresistant organisms and the importance of preserving oral treatment options, fosfomycin should be used judiciously and primarily within its approved indications. Educational interventions aimed at improving awareness of antimicrobial stewardship principles are essential to ensure responsible prescribing practices. Future research should expand these assessments across other specialties and healthcare settings to better inform strategies that safeguard the clinical utility of Fosfomycin.