Effect of Micafungin on Plasma Protein Binding Rate of Ertapenem

OBJECTIVE To establish a method for determining the concentration of free ertapenem in human plasma by HPLC. And to study the effect of micafungin on the plasma protein binding rate of ertapenem. METHODS Sample processed by ultrafiltration. A Diamonsil C₁₈ (4.6 mm×150 mm, 5.0 μm) column was used, with the mobile phase of acetonitrile-10 mmol·L^-1 sodium acetate solution (12.4:87.6) at the flow rate of 1 mL·min^-1, the detection wavelength was 295 nm, column temperature was 35℃ and injection volume was 10 μL. Ultrafiltration was combined with HPLC to determine the plasma protein binding rate of ertapenem after undosing and adding micafungin. RESULTS The method was validated over the concentration range of 2-50 μg·mL^-1 for ertapenem in human plasma, and there was excellent linearity (r=0.999). The recovery rates of low, middle, high dose of ertapenem were (102.3±12.5)%, (97.6±3.1)% and (98.6±2.2)%; the intra-day and inter-day RSD were both <5%. The protein binding rate of ertapenem was no significant change in association with micafungin. CONCLUSION The method for determinating concentration of free ertapenem in plasma is rapid, accurate and sensitive. Micafungin has no effect on the in vitro protein binding rate of ertapenem in human plasma.