Summary.A new sensitive and validated liquid chromatography electro spray iontandem mass spectrometry (HPLC-ESI-MS/MS) method for the quantification of Vildagliptin (VG) in rat plasma has been developed and validated using repaglinide (RG) as an internal standard (IS). The analytes were extracted by liquid-liquid extraction using ethyl acetate. Elution of the VG and IS was achieved on a reverse phase Betasil (C18 50 mm 4.6 mm ID, 5 μ) column with an isocratic mobile phase composed of acetonitrile: 2 mM ammonium acetate (90:10 v/v). The analytes monitored in the Multiple Reaction Monitoring (MRM) mode were m/z 304.2→154.0 and 453.3→230.3 for VG and RG, respectively. The calibration curve was linear in the range of 1.57-501.21 ng/mL for VG with lower limit of quantification 1.57 ng/mL. The intra run and inter run precision values are within 11.70% for VG at LOQ level.

A liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method for the simultaneous quantitation of glipizide, cilostazol and 3, 4-dehydro-cilostazol in rat plasma was developed and validated. Glimepride was used as an internal standard (IS). The analytes were extracted by using liquid-liquid extraction procedure and separated on a reverse phase C18 column (50 mm×4.6 mm i. d., 5 µ) using acetonitrile: 2 mM ammonium acetate buffer, pH 3.2 (90:10, v/v) as mobile phase at a flow rate 0.4 mL/min in an isocratic mode. Selective reaction monitoring was performed using the transitions m/z 446.4>321.1, 370.2>288.3, 368.3>286.2, and 491.4>352.2 to quantify glipizide, cilostazol, 3, 4-dehydro-cilostazol and glimepride, respectively. Calibration curves were constructed over the range of 25-2 000 ng/mL for glipizide, cilostazol and 3, 4-dehydro-cilostazol. The lower limit of quantitation was 25 ng/mL for all the analytes. The recoveries from spiked control samples were>76% for all analytes and internal standard. Intra and inter day accuracy and precision of validated method were within the acceptable limits of at all concentration. The quantitation method was successfully applied for simultaneous estimation of glipizide, cilostazol and 3, 4-dehydro-cilostazol in a pharmacokinetic drug-drug interaction study in wistar rats.