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.