Therapeutic drug monitoring and pharmacogenetics of antipsychotics and antidepressants in real life settings: A 5-year single centre experience.

Objectives: Exposure and clinical response to CNS drugs are largely variable. AGNP guidelines suggest therapy individualisation with therapeutic drug monitoring of plasma concentrations and pharmacogenetic testing. We present the retrospective analysis of the last 5 years' data collected in real life settings as indirect evidence of the applications of the AGNP guidelines in the routine clinical management of psychiatric patients requiring pharmacologic treatments.

Methods: Plasma concentrations were quantified using a liquid chromatography/tandem mass spectrometry method. Genomic DNA was isolated using an automatic DNA extraction system. All genotypes were determined by Real-Time PCR.

Results: We collected a total of 4582 requests for TDM and 212 requests for pharmacogenetic analysis. A wide distribution in the trough concentrations was observed for most drugs indicating a high interpatient variability. Nearly 45% of the samples had trough levels below the minimum effective drug concentrations set by the AGNP guidelines; only 8% of the samples had high concentrations. For pharmacogenetics analysis, among antipsychotics, clozapine, haloperidol and aripiprazole were the most requested (78%); while for antidepressants SSRIs were the most frequently prescribed.

Conclusions: These data suggest that physicians are becoming more confident with the laboratory pharmacologic tools to optimise treatments and/or that the pharmacological treatment of patients with psychiatric disorders is becoming more challenging. TDM and PGx might significantly contribute to the rational selection of the best drug and best dose in individual cases.