Simple, sensitive and rapid LC-ESI-MS method for the quantitation of lafutidine in human plasma - Application to pharmacokinetic studies

A sensitive and specific liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and quantification of lafutidine in human plasma. Lafutidine and internal standard were isolated from plasma samples by liquid-liquid extraction with diethyl ether. The chromatographic separation was accomplished on a stainless-steel column (C₁₈ Shim-pack 5 μm 150 mm × 2.0 mm i.d. Shimadzu) at a flow rate of 0.2 ml/min by a gradient elution. Detection was performed on a single quadrupole mass spectrometer by selected ion monitoring (SIM) mode via electrospray ionization (ESI) source. The method was proved to be sensitive and specific by testing six different plasma batches. Linearity was established for the range of concentrations 1.0-400.0 ng/ml with a coefficient of determination (r) of 0.9998 and good back-calculated accuracy and precision. The intra- and inter-day precision (R.S.D.%) was lower than 10% and accuracy ranged from 85 to 115%. The lower limit of quantification was identifiable and reproducible at 0.5 ng/ml with 0.2 ml plasma. The proposed method enables the unambiguous identification and quantification of lafutidine for pharmacokinetic, bioavailability or bioequivalence studies.