Determination of fexofenadine enantiomers in human plasma with high-performance liquid chromatography

A simple and sensitive high-performance liquid chromatography (HPLC) method was developed as an assay for fexofenadine enantiomers in human plasma. Fexofenadine enantiomers were separated using a mobile phase of 0.5% KH(2)PO(4)-acetonitrile (65:35, v/v) on a Chiral CD-Ph column at a flow rate of 0.5 ml/min and measurement at 220 nm. Analysis required 400 microl of plasma and involved solid-phase extraction with an Oasis HLB cartridge, which gave recoveries for both enantiomers from 67.4 to 71.8%. The lower limit of quantification was 25 ng/ml for (R)- and (S)-fexofenadine. The linear range of this assay was between 25 and 625 ng/ml (regression line r(2)>0.993). Inter- and intra-day coefficients of variation were less than 13.6% and accuracies were within 8.8% over the linear range for both analytes. This method can be applied effectively to measure fexofenadine enantiomer concentrations in clinical samples.