Quantification of anidulafungin and micafungin in human body fluids by high performance-liquid chromatography with UV-detection.

The echinocandins anidulafungin (ANID) and micafungin (MICA) are recommended for treatment of invasive Candida infections. As target-site concentrations of antimicrobial agents are crucial for eradication of pathogens, we established and validated high-performance liquid chromatography-UV detection (HPLC-UV) assays for quantification of ANID and MICA in human plasma, ascites fluid, pleural effusion, and in cerebrospinal fluid (CSF). Sample pre-purification was performed by protein precipitation with acetonitrile followed by solid phase extraction. For both assays, intra- and interday precision, and accuracy fulfilled the requirements for bioanalytical methods issued by the European Medicine Agency (EMA). The lower limit of quantification was 0.01 mg/L for both drugs. At 25 °C, ANID and MICA concentrations declined by up to 70% within 24 h. Concentrations remained stable over 24 h at 4 °C and over four weeks at -80 °C. In conclusion, the developed methods are fit for the assessment of target-site pharmacokinetics of ANID and MICA in clinical studies.