A rapid liquid chromatography-tandem mass spectrometry for the quantification of Fosfomycin in plasma, urine, and aqueous fluids

- A robust and fast UPLC-MS/MS method is developed for the quantification of Fosfomycin in plasma, urine, and aqueous fluid.
- The method is precise and accurate.
- Sample preparation consists of a simple protein precipitation or dilution depending on the matrix used.
- The method is suitable for therapeutic drug monitoring & for pharmacokinetic studies.

A simple and fast ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the analysis of Fosfomycin in different matrices (human plasma/urine, and aqueous fluid) has been established and validated. Sample cleanup consists, depending on the matrix used, on protein precipitation or dilution with methanol containing isotopically labeled Fosfomycin as internal standard. Compounds, separated on a Luna Omega PS C18 column, were detected in multiple reactions monitoring in negative ion mode using API4000 system. With a total run time of 2 min and using low volume of samples (plasma: 10 μl, urine: 2 μl, and aqueous fluid: 5 μl), the covered ranges were: plasma (12.5-800 μg/mL), urine (62.5-4000 μg/mL), and aqueous fluid (1-160 μg/mL). The method proved to be precise and accurate. The inaccuracy and imprecision in each matrix at the four tested quality controls including the lower limit of quantification were:: plasma (≤ 6.5%, ≤ 8%), urine (≤ 5.8%, ≤ 6.3%), and aqueous fluid (≤ 10.6%, ≤12%). The method is fast and robust which makes it relevant for pharmacokinetic studies and therapeutic drug monitoring. The appropriateness of the developed method in clinical application is also confirmed.