Abstract: AIM: To establish a highly sensitive method for the quantitation of terfenadine in human plasma by using high performance liquid chromatogramelectrospray ionization-mass spectrometry (LC-ESIMS).METHODS: Flunarizine was chosen as the internal standard (I.S.) , the plasma was extracted by ethyl acetate after alkalized with 2 mol L sodium hydroxide, and the Phenomenex C18 chromatographic column(250 mm ×4.6 mm, 5 μm) was used, the column temperature was 25 ℃, the mobile phase was methanol-water(80∶20) including 1 %glacial acetic acid and 0.5 % triethylamine.The flow rate was 1 mL/min.Analytes were quantitated using positive electrospray ionization in a quadrupole spectrometer.The selected ion monitoring(SIM) mode was detected , terfenadine m z was 472 and flunarizine m z was 203.RESULTS: The linear range was 0.1 -20 ng mL, the lowest detectable limit was 0.05 ng mL (S N >3) , The intra and inter-assay precision of terfenadine was 2.54 %-9.28 %.The recovery of terfenadine in plasma was 88.62 % -91.67 %.CONCLUSION: The method has strong specificity and high sensitivity and can be used for clinical experiment of terfenadine pharmacokinetic study.

Key words: terfenadine, HPLC-MS, plasma, determination