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HIGH THROUGHPUT AND SENSITIVE LC-MS/MS METHOD FOR THE ESTIMATION OF VENLAFAXINE AND ITS ACTIVE METABOLITE O-DESMETHYL VENLAFAXINE IN HUMAN PLASMA AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

A highly sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of venlafaxine (VEN) and its active metabolite O-desmethyl venlafaxine (ODV) in human plasma using fluoxetine as an internal standard. The VEN and ODV were extracted by liquid–liquid extraction using MTBE-n Hexane (60:40), and chromatographed on X-terra RP8 (50 mm × 4.6 mm, 5-µm particle size) column eluted with a isocratic mobile phase of 10 mM Ammonium acetate (pH 4.50 ± 0.05) and acetonitrile in 10:90 (v/v). The detection was performed by positive ion electrospray ionization in multiple reactions monitoring mode, monitoring the transitions m/z 278.27→ 121.08 and 264.33 → 57.72 for venlafaxine and O-desmethyl venlafaxine, respectively. The assay was linear over the concentration ranges of 0.100–300.010 ng/mL for VEN and 0.200–600.050 ng/mL for ODV with limits of detection and quantification of 0.050 ng/mL for VEN and 0.100 ng/mL for ODV, respectively. This LC-MS/MS method was validated with Intra-batch and Inter-batch precision 1.65–10.80 for VEN and 1.27–7.08 for ODV, respectively. The Intra-batch and Inter-batch %accuracy was 91.77%–104.39% for VEN and 95.87%–106.28% for ODV, respectively. This method was successfully applied to a pharmacokinetic study of venlafaxine hydrochloride extended release capsules 150 mg steady-state bioequivalence study.