Determination of phenothiazine concentration in serum – The importance of a suitable column

Background: The therapeutic usage of Flupentixol is due to its efficacy as an antipsychotic drug. The approximate concentration for a satisfactory antipsychotic effect is 1–10 ng/ml. This low therapeutic range made the serum therapeutic drug monitoring of this drug very important. It will contribute in areas of clinical and forensic applications in optimising the patients' therapy. Material and Method: Choosing a suitable HPLC-Column for a given method is one of the factors that determines the reliability and accuracy of the measurements during a method development. A high-performance liquid chromatographic method with an UV-Detector was used. The pool human serum was donated by the university clinic in Regensburg (Germany). The columns used were Luna-Phenyl-Hexyl, Thermo-Betasil, SphereClone ODS und Nucleodur. The analytic solvent was a mixture of Acetonitrile-Methanol-Water. Result: For the determination of Flupentixol in the Serum sample, the use of Nucleodur column and 43% of organic solvent was found to be optimal. The serum levels were linear and the amount yielded corresponds to the given and expected amount. Conclusion: The accuracy and precision of this method is satisfactory. Pre-treatment procedures of the samples were not necessary. For the further improvement of the individual patients' therapy, it is to be recommended as a faster method in the therapeutic drug monitoring of Flupentixol.