Liquid chromatographic determination of fexofenadine in human plasma with fluorescence detection

A simple and sensitive method was developed for determination of fexofenadine by liquid chromatography with fluorescence detection. Fexofenadine in human plasma was extracted on a C18 bonded-phase extraction cartridge. The mobile phases were: (A) 0.05 M KH2PO4 buffer/acetonitrile/methanol (60:35:10, v/v/v) and (B) 0.05 M KH2PO4 buffer/acetonitrile (40:60, v/v). Chromatographic separation was achieved on an ODS-80A column (150 mm x 4.6 mm i.d., particle size 5 microm) using a linear gradient from A to B in 10 min. The peak was detected using a fluorescence detector set at Ex 220 nm and Em 290 nm, and the total time for a chromatographic separation was approximately 17 min. The validated quantitation ranges of this method were 1.0-500 ng/ml with coefficients of variation of 0.6-9.1%. Mean recoveries were 72.8-76.7% with coefficients of variation of 2.7-5.8%. This method is successfully applicable for therapeutic drug monitoring in patients treated with clinical doses of fexofenadine and for analyses within pharmacokinetic studies.