Determination of lafutidine in human plasma by high-performance liquid chromatography-electrospray ionization mass spectrometry: application to a bioequivalence study

A rapid, sensitive and specific high-performance liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) method was developed and validated for the first time to determine the concentration of lafutidine in human plasma. After the addition of diazepam (the internal standard, IS) and 1 m sodium hydroxide solution to 0.5-ml plasma sample, lafutidine was extracted from plasma with n-hexane: isopropanol (95: 5, v/v). The organic layer was evaporated and the residue was redissolved in 200-mu l mobile phase. The analyte was chromatographically separated on a prepacked Shimadzu Shim-pack VP-ODS C-18 column (250 x 2.0 ram i.d.) using a mixture of methanol-water (20 mm CH3COONH4) = 80:20 (v/v) as mobile phase. Detection was performed on a single quadrupole mass spectrometer using an electrospray ionization interface and the selected-ion monitoring (SIM) mode. The method showed excellent linearity (r- = 0.9993) over the concentration range of 5-400 ng/ml and had good accuracy and precision. The within- and between-batch precisions were within 10% relative standard deviation. The limit of detection was 1 ng/ml. The validated LC/ESI-MS method has been successfully applied to the bioequivalence study of lafutidine in 24 healthy male Chinese volunteers. Copyright (c) 2005 John Wiley & Sons, Ltd.