Simple column-switching HPLC method for determining levels of the antifungal agent micafungin in human plasma and application to patient samples.

Micafungin is an echinocandin antifungal agent that is important for treating candidiasis in emergency and intensive care medicine; however, current methods for measuring micafungin plasma levels are lengthy and complicated. We report a simple quantitative method using column-switching high-performance liquid chromatography (HPLC) for determining micafungin in human plasma samples. Human plasma was directly injected into a column-switching HPLC system with a MAYI-ODS pre-column to remove the plasma matrix. The calibration curve for micafungin showed good linearity in the range 0.1-10 µg/mL in human plasma. The mean relative standard deviation value of the intra-day and inter-day precision was less than 7.3%. More than 450 successive, accurate measurements were made before the system had to be washed with ammonium acetate solution. The therapeutic micafungin level in patients' plasma was successfully measured using this method. Because the pretreatment is simple and reproducible, our method can be used for routine therapeutic monitoring.