Liquid chromatography-tandem mass spectrometric assay for the determination of tetrabenazine and its active metabolites in human plasma: A pharmacokinetic study

Abstract

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for the simultaneous quantification of tetrabenazine and its active metabolites α-dihydrotetrabenazine and β-dihydrotetrabenazine in human plasma. Tetrabenazine d7 was used as internal standard (IS). The analytes were extracted from 200 μL aliquots of human plasma via solid-phase extraction using C18 solid-phase extraction cartridges. The reconstituted samples were chromatographed on a Zorbax SB C18 column using a 60:40 (v/v) mixture of acetonitrile and 5mm ammonium acetate as the mobile phase at a flow rate of 0.8mL/min. The API-4000 LC-MS/MS in multiple reaction-monitoring mode was used for detection. The calibration curves obtained were linear (r2 ≥ 0.99) over the concentration range of 0.01-5.03ng/mL for tetrabenazine and 0.50-100ng/mL for α-dihydrotetrabenazine and β-dihydrotetrabenazine. Method validation was performed as per Food and Drug Administration guidelines and the results met the acceptance criteria. The method is precise and sensitive enough for its intended purpose. A run time of 2.5min for each sample made it possible to analyze more than 300 plasma samples per day. The proposed method was found to be applicable to clinical studies. © 2013 John Wiley & Sons, Ltd.