Therapeutic drug monitoring: chemical-clinical correlations of atypical antipsychotic drugs.

In the last few years, new drugs for the treatment of schizophrenia have been introduced in therapy which have noticeably improved the quality of life of many schizophrenic patients. These new "atypical" drugs have chemical, pharmacological and clinical properties which are different from those of the classical neuroleptics. The most used drugs among the "atypical" antipsychotics are clozapine, olanzapine, quetiapine and risperidone. Despite several differences in their pharmacokinetic and pharmacodynamic profiles, they show some common properties: e.g. they don't cause extrapyramidal side effects, and they are active against the negative as well as positive symptoms of schizophrenia. The need for clinical monitoring of patients undergoing therapy is still evident because the onset of side effects is often related to high plasma concentrations of the drug. The clinical monitoring of patients can significantly improve the knowledge of pharmacological interactions among different CNS drugs, as well as enhance the compliance of the patients, thus leading to higher treatment efficacy. In order to carry out efficient clinical monitoring, reliable analytical methods are needed to determine the analytes even at very low concentrations and in the presence of other drugs. For this purpose, analytical techniques such as gas or liquid chromatography are often used coupled with sensitive and selective means of detection, such as fluorimetric, electrochemical or mass spectrometry detectors. The most recent studies on the determination of atypical antipsychotics will be reviewed in addition to the issue of sample pretreatment which is a critical step when the analysis of biological fluids is concerned.