Abstract: Aim To develop and validate a sensitive and specific liquid chromatography electrospray ionization ion-trap mass spectrometry (LC-ESI-MS/MS) method for the identification and concentration of rupatadine in human plasma. Methods After the addition of the internal standard (IS, loratadine) and 0.01 mol·L^–1 sodium hydroxide solution, plasma samples were extracted with methylene chloride: ethyl acetate mixture (20:80, V/V). The organic layer was evaporated under vacuum drying at 37 ºC. The residue was reconstituted with 200 μL mobile phase. Chromatography was performed on an Agilent Eclipse XDB-C18 (4.6 mm × 150 mm, 5 μm) column with a mobile phase consisting of acetonitrile (1% formic acid) –20 mmol·L^–1 ammonium acetate (76:24, V/V) at a flow-rate of 0.6 mL·min^–1. Detection was performed on Agilent MSD Trap XCT ion-trap mass spectrometry connected to a Agilent 1100 high performance liquid chromatography (HPLC) by selected reaction monitoring (SRM) mode via electrospray ionization (ESI) source. Rupatadine (MRM m/z 416→309) and loratadine (MRM m/z 383→337) were detected by Agilent MSD Trap XCT ion-trap mass analyser. Results The method was proved to be sensitive and specific by testing 20 different plasma batches. Linearity was established for the range of concentrations 0.05 – 14.0 ng·mL^–1 with a coefficient of determination (r) of 0.998. The intra-and inter-day precision (RSD %) were lower than 15% and accuracy ranged from 85.1% to 114.0%. The lower limit of quantitation (LLOQ) was identifiable and reproducible at 0.05 ng·mL^–1 with a precision of 9.22% (n = 5). Conclusion The proposed method is sensitive and reproducible enough to be used in pharmacokinetic, bioavailability or bioequivalence studies of rupatadine.

Key words: Rupatadine, Rupatadine, HPLC-ESI-MS/MS, HPLC-ESI-MS/MS, Human plasma, Human plasma, Pharmacokinetics, Pharmacokinetics