Oral Fosfomycin Matches IV Carbapenems as Oral Transition Therapy for Complicated UTIs: Study
Written By : Medha Baranwal
Medically Reviewed By : Dr. Kamal Kant Kohli
Published On 2026-07-14 15:15 GMT | Update On 2026-07-14 15:15 GMT
South Korea: A randomized clinical trial from South Korea found that oral fosfomycin was noninferior to intravenous (IV) carbapenem antibiotics as step-down (transition) therapy for patients with complicated urinary tract infections (cUTIs) caused by multidrug-resistant bacteria.
The findings suggest that oral fosfomycin may serve as an effective alternative to prolonged IV carbapenem treatment, potentially reducing hospitalization, lowering healthcare costs, and supporting antibiotic stewardship while maintaining comparable clinical outcomes.
The study, published in Clinical Infectious Diseases, was conducted by Jun-Won Seo and colleagues from the Department of Internal Medicine, College of Medicine, Chosun University, Republic of Korea.
Complicated urinary tract infections (cUTIs) caused by ESBL-producing Enterobacterales are increasingly common and often require carbapenem treatment due to resistance to multiple antibiotics. However, rising carbapenem use may contribute to antimicrobial resistance, creating a need for effective oral alternatives.
To evaluate one such option, researchers conducted a multicenter, open-label, randomized noninferiority trial across four tertiary hospitals in South Korea from November 2022 to June 2025. The study included hospitalized adults with ESBL-producing Enterobacterales cUTIs who had improved after 3–7 days of intravenous antibiotic therapy.
Participants were randomized to either continue intravenous carbapenem or β-lactam/β-lactamase inhibitor therapy or switch to oral fosfomycin trometamol 3 g once daily. The primary outcome was clinical cure within four days of treatment completion. Secondary outcomes included microbiological cure, adverse events, hospital readmissions, and 30-day recurrence.
The trial led to the following findings:
- Of 344 screened patients, 299 were randomized, with 152 assigned to oral fosfomycin and 147 to continued intravenous therapy.
- Clinical cure was achieved in 92.8% of patients receiving oral fosfomycin and 95.2% of those receiving intravenous therapy, demonstrating noninferiority of oral fosfomycin.
- Microbiological cure rates in urine cultures were high and comparable between the oral fosfomycin and intravenous therapy groups (98.0% vs 96.6%).
- Clearance of bloodstream infections was also similar between the two groups, occurring in 97.3% of patients receiving oral fosfomycin and 97.5% of those receiving intravenous therapy.
- Safety profiles were comparable between oral fosfomycin and continued intravenous treatment.
- Rates of adverse events, hospital readmissions, and 30-day infection recurrence did not differ meaningfully between the two treatment groups.
- Transitioning to oral fosfomycin maintained clinical effectiveness and safety while achieving outcomes comparable to continued intravenous therapy.
The researchers concluded that oral fosfomycin can be considered a viable transition therapy for patients with complicated UTIs caused by ESBL-producing Enterobacterales who have responded to initial IV treatment. They noted that adopting this approach could help preserve carbapenem use, reduce the burden associated with prolonged intravenous therapy, and strengthen antimicrobial stewardship efforts without sacrificing clinical outcomes.
Reference:
Seo, J. W., Kim, D. Y., Yoon, Y., Lyu, Y. S., Na, Y. S., Moon, D. S., Yun, N. R., Kim, M. S., Kim, J. H., Bae, S. W., Hur, J., Kim, M. H., Park, Y. S., Kim, H., Lee, H., On, Y., Na, S. H., Yoo, J. S., Jang, H. C., . . . Kim, D. M. Fosfomycin as Oral Transition Therapy Versus Continued Intravenous β-Lactams for Complicated Urinary Tract Infections Caused by Extended-Spectrum β-Lactamase–Producing Enterobacterales: A Multicenter, Open-Label, Randomized Controlled Trial. Clinical Infectious Diseases. https://doi.org/10.1093/cid/ciag345
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