A simple,sensitive,and specific liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of desloratadine (DL) in human plasma using desloratadine-d5 (DLD5) as an internal standard (IS).Chromatographic separation was performed using an Xbridge C18 column (50 mm × 4.6 mm,5 μm) with an isocratic mobile phase composed of 10 mM ammonium formate:methanol (20∶80,v/v),at a flow rate of 0.7 mL/min.DL and DLD5 were detected with proton adducts at m/z 311.2→259.2 and 316.2→264.3 in multiple reaction monitoring (MRM)positive modes,respectively.Liquid-liquid extraction (LLE) method was used to extract the drug and the IS.The method was validated over a linear concentration range of 5.0-5000.0 pg/mL with a correlation coefficient of (r2)(≥)0.9994.This method demonstrated intra- and inter-day precision within 0.7-2.0％ and 0.7-2.7％,and an accuracy within 101.4-102.4％,and 99.5-104.8％.DL was found to be stable throughout the freeze-thaw cycles,bench-top,and postoperative stability studies.This method was successfully applied in the analysis of plasma samples following oral administration of DL (5 mg) in 35healthy Indian male human volunteers under fasting conditions.