High-performance liquid chromatography–mass spectrometry method for the determination of paroxetine in human plasma

A rapid and specific liquid chromatographic mass spectrometric (LC–MS–MS) method has been developed for the determination of paroxetine in human plasma. The procedure involves a liquid–liquid extraction of paroxetine and fluoxetine (internal standard) with cyclohexane–ethyl acetate. The standard curve was linear over a working range of 0.2–50 ng/ml. The lower limit of quantitation was 0.2 ng/ml. No endogenous compounds were found to interfere with the analysis. The absolute recovery was 70.8% for paroxetine and 84.1% for the internal standard. The accuracy of inter-assay and intra-assay accuracy was in the ranges −4.8 to −0.5% and −3.4 to 4.8%, respectively. This method proved to be suitable for bioequivalence studies by being simple, selective and reproducible.