Assay of Fexofenadine Concentrations in Human Plasma by HPLC with Fluorescence Detector

OBJECTIVE To establish an HPLC for determination of fexofenadine(FEX) concentrations in human plasma. METHODS Plasma samples(200 mL) were deproteinized by precipitation with acetonitrile, centrifuged and the supernatant was reconstituted and injected into HPLC. Separation was achieved on Waters Symmetry C18(4.6 mm×250 mm, 5 mm) with a mixture of 0.1 mol·L^-1 ammonium acetate-acetonitrile(63∶37) as mobile phase. The flow rate was 1 mL·min^-1. The fluorescence detector was set at excitation wavelength of 230 nm and emission wavelength of 290 nm. Diphenhydramine was used as internal standard. The assay was validated and applied to pharmacokinetic study of FEX in 4 healthy volunteers following a single oral dose of 120 mg FEX tablet. RESULTS Endogenous chemicals and metabolite did not interfere with FEX. The calibration curves were linear in the range of 20-1 000 mg·L^-1(r=0.999 3, n=6), with a limit of quantitation of 20 mg·L^-1. The within- and between-day RSDs of quality-control samples at high-, medium- and low-concentrations were less than 10％. The average method recovery was 105.9%. The average absolute recovery was 94.6%. Major mean pharmacokinetic parameters included Cmax(733 mg·L^-1), t_max(2.5 h), AUC_0-t(3 954 mg·h·L^-1) and the data were similar with documented data abroad. CONCLUSION The assay is stable, simple, rapid, accurate, sensitive and applicable for determining plasma concentrations of FEX in its pharmacokinetic studies.