Efficacy and Safety of Fosfomycin Disodium in Patients with Bacterial Infections: A Single-Center, Real-Life Clinical...

Objectives: Fosfomycin is an old antibiotic that has recently gained attention owing to its preserved activity against multidrug-resistant (MDR) bacteria. Data on its use in real life are limited. Thus, we evaluated the efficacy and safety of fosfomycin disodium in the context of our hospital clinical practice. Methods: Single-center, retrospective, observational study on 56 patients who received fosfomycin disodium from September 2016 to July 2023, focusing on clinical and microbiological outcomes and adverse events. Results: Included in this study were 56 patients. Fosfomycin disodium was administered for a median duration of 10 days [5-13.5] and was always used in combination with other antibiotics, more frequently with meropenem (16 cases, 28.6%) and colistin (11 cases, 19.6%). It was mostly used for treating pneumonia (41%), followed by bloodstream infections (19.6%), urinary tract infections (16.1%), bone infections (16.1%), and surgical site infections (7.1%). The most common isolated pathogen was Pseudomonas aeruginosa (17%), and polymicrobial infections were detected in 18 patients (32%). Among the isolated bacteria, 36 (44.4%) were MDR. The complete resolution, defined as the disappearance of symptoms, eradication of the causative microorganism, and decrease in CRP levels, was achieved in 39% of cases. During treatment, we observed electrolyte imbalances, in particular a decrease in serum potassium (0.6 mEq/L [0.3-1.1]), calcium (0.7 mEq/L [0.3-1.1]) and magnesium levels (0.3 mg/dL [0.20-0.48]), and an increase in serum sodium levels (4 mEq/dL [2-7]). Changes in potassium and sodium levels were more pronounced in patients with prior kidney dysfunction and heart failure, respectively, and in patients receiving fosfomycin diluted with saline compared with 5% glucose solution (p = 0.04). Conclusions: Fosfomycin is effective in treating complicated infections in comorbid patients when combined with other antimicrobials. During treatment, major electrolyte imbalances occur that require careful monitoring and correction, especially in patients with prior kidney disease.