Determination of Dothiepin in Human Plasma by LC–ESI–MS and its Application to Bioequivalence Studies

Abstract

An LC–MS method for the determination of dothiepin in human plasma was developed and validated. Sample preparation involved extraction with n-hexane:2-propanol (95:5). Separation was on an Ultimate XB C18 column (2.1 × 150 mm, 5 μm). A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H]+ ions at m/z 296 for dothiepin and at m/z 278 for the internal standard (amitriptylene). The method demonstrated good linearity from 0.78 ng mL−1 (the LOQ) to100 ng mL−1. The mean extraction recovery was 82.4% for dothiepin and and 84.2% for the internal standard. The intra-day and inter-day precision ranged from 8.5 to 11.4% and 9.7 to 12.1% (RSD), respectively. The method was successfully applied to bioequivalence studies of dothiepin hydrochloride tablets to obtain the pharmacokinetic parameters.