Background: This contribution is a study on plasma antipsychotics concentrations of first episode outpatients with psychosis (FEPs), under antipsychotic treatment; it aims to attract attention to the importance of the drug-driven management of psychiatric patients for improving adherence and clinical efficacy.
Methods: The plasma antipsychotic concentrations were determined retrospectively (after the completion of selection of all samples) and therefore, they were not used to monitor patients’ response to pharmacotherapy. A total of 120 plasma samples from 35 psychiatric patients were collected and tested for antipsychotics. The concentrations of eight antipsychotic drugs (amisulpride, aripiprazole, clozapine, haloperidol, olanzapine, quetiapine, risperidone and paliperidone) and seven of their metabolites were determined.
Results: Overall, 74% of the samples had therapeutic antipsychotic levels, 19% had subtherapeutic concentrations, while supra-therapeutic concentrations were measured for clozapine (7%). Therapeutic drug concentrations were recorded in 54% of plasma samples from patients being under olanzapine medication and in all patients under long-acting injectables. Sub-therapeutic levels were either attributed to non-adherence, or they reflected residual levels due to medication changes. Supra-therapeutic levels were recorded for clozapine and were not followed by adverse effects.
Conclusion: This is the first study on antipsychotic plasma levels conducted in Greece. Our results show the importance of performing measurement of plasma antipsychotics levels, at appropriate time intervals, for improving adherence, clinical decision making and thus clinical efficacy. Especially for FEPs, such approach could contribute to early detection of treatment limitations and improve outcome.