Determination of paroxetine in plasma by high-performance liquid chromatography for bioequivalence studies

A high-performance liquid chromatographic method is described for the determination of paroxetine in human plasma. Dibucaine was used as the internal standard. Paroxetine was isolated by solid phase extraction using a Bond-Elut C18 extraction column. Separation was obtained using a reversed-phase column under isocratic conditions with fluorescence detection. The sample volume was 500 microliters of plasma. The intra- and inter-assay accuracy and precision, determined as relative error and relative standard deviation, respectively, were less than 10%. The lower limit of quantitation, based on standards with acceptable relative error and relative standard deviation, was 10 ng ml-1. No endogenous compounds were found to interfere. The linearity was assessed in the range 5-100 ng ml-1. Stability of paroxetine during processing (autosampler) and in plasma was checked. This method proved suitable for bioequivalence studies following multiple doses in healthy volunteers.