Quantitative analysis of trazodone in human plasma by using HPLC-fluorescence detector coupled with strong cation exchange chromatographic column: application to a pharmacokinetic study in Chinese healthy volunteers.

A simple, selective, and sensitive high performance liquid chromatography (HPLC) procedure has been developed for determination of trazodone in human plasma. Prazosin was employed as the internal standard (IS). Sample preparation involved liquid-liquid extraction by methyl tert-butyl ether after alkalinization with ammonia. The HPLC separation was performed on a CAPCELL PAK SCX column (250mm×4.6mm, 5.0μm, Shiseido, Japan) with a mobile phase of acetonitrile/80mmol/L ammonium phosphate (pH adjusted to 6.0) (60:40, v/v) at a flow rate of 1.2mL/min. The peaks were detected by using fluorescence detector (excitation wavelength 320nm and emission wavelength 440nm). The extraction recovery was 72.6-88.3% and the method was over the concentration range of 5.0-2486ng/mL with a lower limit of quantitation (LLOQ) of 5.0ng/mL using 300μL of plasma. The intra- and inter-day accuracy of the method at three concentrations ranged from 96.7% to 104.2% for trazodone with precision of 2.9-3.7%. This validated method was successfully applied to a pharmacokinetic study enrolling 12 Chinese volunteers administered a single oral trazodone hydrochloride extended-release tablet of 75mg.