[Therapeutic drug monitoring of olanzapine]

Olanzapine, atypical antipsychotic, is used to treat schizophrenia and bipolar disorder. Its therapeutic drug monitoring (TDM) is quite commonly done. Olanzapine is well absorbed orally (bioavailability: 85 %), with peak plasma occurring between 4 and 6hours after oral administration. It is extensively metabolized by different hepatic enzymes (including CYP1A2 and CYP2D6 isoforms) to a large number of inactive metabolites, and its half-life is between 30 and 60hours. No specific therapeutic range, or threshold concentration could not be a consensus, but the higher intra- and interindividual variability, as well as the existence of studies suggesting a correlation between circulating concentrations of olanzapine and occurrence of therapeutic relapse or toxic phenomena appear to justify the STP for this molecule. Given these data, the interest of the STP was evaluated for this molecule to: recommended with therapeutic window of 20μg/L to 80μg/L.