Objective: To determine the microbiological activity in serum and urine of healthy subjects against extended-spectrum betalactamase (ESBL)-producing Escherichia coli compared between original brand and generic oral fosfomycin trometamol.

Materials and Methods: This randomized crossover study was conducted at Siriraj Hospital. Fourteen healthy subjects with a mean age of 34.14 years received a single 3-gram dose of either original brand fosfomycin trometamol (Monurol®) or generic oral fosfomycin trometamol (Fosfomet®). After a 1-week washout, both groups were switched to the other medication and the process was repeated. Blood samples and urine samples were collected from each subject at baseline before drug administration, and then at 1, 2, 5, and 8 hours after taking the study drug. Another urine sample was collected on day 2 of the study. Inhibitory activity against ESBL-producing E. coli was evaluated by disk diffusion method, and bactericidal activity was evaluated by broth microdilution method.

Results: Inhibitory activity and bactericidal activity in serum and urine samples against ESBL-producing E. coli was highest between 2 and 5 hours after administration of the study drugs. Inhibitory and bactericidal activity in serum samples were both less and shorter than those observed in urine samples. Urine samples continued to demonstrate high inhibitory and bactericidal activity at 24 hours after drug administration. There were no significant differences in inhibitory or bactericidal activities in serum or urine samples when compared between administration of original brand fosfomycin trometamol (Monurol®) and administration of generic oral fosfomycin trometamol (Fosfomet®). Mild diarrhea was the only adverse event observed, and there was no significant difference in this side effect between groups.

Conclusion: Inhibitory activity, bactericidal activity, and rate of adverse events were all found to be comparable between original brand fosfomycin trometamol (Monurol®) and generic oral fosfomycin trometamol (Fosfomet®).

Keywords: Microbiological activity, Fosfomycin trometamol, Extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli

Received 10 May2019 | Revised 17 May 2019 | Accepted 21 May 2019