Highly sensitive LC–MS/MS method to estimate doxepin and its metabolite nordoxepin in human plasma for a bioequivalence study

Publication date: Available online 16 June 2017Source: Journal of Pharmaceutical AnalysisAuthor(s): Nirav P. Patel, Mallika Sanyal, Naveen Sharma, Dinesh S. Patel, Pranav S. Shrivastav, Bhavin N. PatelAbstractA selective, sensitive and rugged liquid chromatography–tandem mass spectrometry (LC–MS/MS) assay has been developed for the simultaneous determination of doxepin (Dox) and its pharmacologically active metabolite, nordoxepin (NDox) in human plasma. The analytes and their internal standards (IS) were extracted from 500 µL of human plasma by liquid-liquid extraction using methyl tert-butyl ether. Chromatographic separation was achieved on Hypurity C8 column (100 mm × 4.6 mm, 5 µm) using a mixture of acetonitrile-methanol (95:5, v/v) and 2.0 mM ammonium formate in 93:7 (v/v) ratio. Detection was accomplished by tandem mass spectrometry in the positive ionization and multiple reaction monitoring acquisition mode. The protonated precursor to product ion transitions studied for Dox, NDox, and their corresponding ISs, propranolol and desipramine, were m/z 280.1→107.0, 266.0 →107.0, 260.1→116.1 and 267.1→72.1 respectively. A linear dynamic range of 15.0–3900 pg/mL for Dox and 5.00–1300 pg/mL for NDox was established with mean correlation coefficient (r2) of 0.9991 and 0.9993 respectively. The extraction recovery ranged from 86.6% − 90.4% and 88.0%–99.1% for Dox and NDox respectively. The intra-batch and inter-batch precis...
Source: Journal of Pharmaceutical Analysis - Category: Drugs & Pharmacology Source Type: research