The present study aims at developing a simple, sensitive and specific liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the quantification of Esomeprazole (EO) in human plasma using Omeprazole-d3 (OMD3) as an internal standard (IS). Chromatographic separation was performed on Xbridge C18, 50 x 4.6 mm, 5 mm column with an isocratic mobile phase composed of 5mM Ammonium formate (pH 9.0) : Acetonitrile (70:30 v/v) at a flow-rate of 0.6 mL/min. EO and OMD3 were detected with proton adducts at m/z 346.1®198.0 and 349.0®197.9 in multiple reaction monitoring (MRM) positive mode respectively. EO and OMD3 were extracted by Precipitation method. The method was validated over a linear concentration range of 5.0-2000.0 ng/mL with a correlation coefficient of (r2) ≥ 0.9989. This method demonstrated intra and inter-day Precision within 1.6 to 2.3 and 2.0 to 2.2 % and Accuracy within 97.9 to 100.7 and 98.0 to 99.3 %. EO was found to be stable throughout freeze-thawing cycles, bench top and postoperative stability studies. This method was utilized successfully for the analysis of plasma samples following oral administration of EO (40 mg) in 27 healthy Indian male human volunteers under fasting conditions.
