Plasma monitoring: a challenge for and of the laboratory

1. Introduction. The therapeutic drug monitoring (TDM) of psychiatric patients is advisable, with the aim of reducing side effects and optimizing the therapy, and is a particularly useful tool if one considers the poor compliance of treated patients. TDM, starting from clinical-chemical correlation data, allows therapy personalization according to the specific needs of the patient. This in turn leads to increased compliance and improved efficacy and finally also to lower total treatment expenses, due to the reduction in hospitalisation length and frequency. 2. Materials and Methods. Performing the TDM obviously requires reliable analytical methods. These normally consist in a sample pre-treatment, which is a critical step for the removal of biological interferences, and the following analysis using liquid chromatography or capillary electrophoresis, coupled with different detectors selected on the basis of the drug chemical structures and expected plasma levels. Therefore, the methods and the corresponding techniques should possess adequate sensitivity and selectivity for the particular analytical problem. 3. Results. Psychiatric patients are very often subjected to polypharmacy: for example, with antipsychotic and anxiolytic-hypnotic drugs for the treatment of schizophrenia; or with atypical antipsychotics (quetiapine, olanzapine) and antiepileptic agents (lamotrigine, oxcarbazepine) for bipolar disorder. This fact constitutes a great challenge for both psychiatrists and analytical laboratories. 4. Conclusion. The possibility of unwanted drug interactions is a constant threat during polypharmacy; drug metabolism can be strongly influenced by the administration of other drugs or by their metabolites, and this can lead to toxicity, when a reduced metabolism is observed, or to a lack of response to therapy in the opposite case. The presence of numerous drugs and metabolites in the patient plasma makes the analytical problem, as well as the interpretation of the resulting analytical data, much more complicated. At the same time, it is precisely this kind of challenge that makes it so exciting and interesting to work on plasma monitoring.