Simultaneous determination of paroxetine, risperidone and 9-hydroxyrisperidone in human plasma by high-performance liquid chromatography with coulometric detection.

A method for the simultaneous determination of paroxetine, risperidone and its main metabolite 9-hydroxyrisperidone in human plasma has been developed. The procedure involved a multistep solid-phase liquid extraction with an internal standard. The drugs were separated on a cyano column followed by coulometric detection. This method described here has sufficient sensitivity to quantitate paroxetine accurately in the range 5-500 ng/ml with a lower limit of detection of 1 ng/ml and risperidone and its main metabolite 9-hydroxyrisperidone in the range 2-100 ng/ml with a lower limit of detection of 1 ng/ml when 1 ml of plasma was used for the analysis. The precision, accuracy and specificity have been proven, and show that the method is reliable for clinical studies and routine drug monitoring. Copyright 2000 S. Karger AG, Basel