THERAPEUTIC DRUG MONITORING OF ANTIPSYCHOTICS

Antipsychotics are drugs that are primarily used in the management of schizophrenia and other disorders with psychotic features [1]. There are many antipsychotics available for clinical use [2]. They are traditionally divided into two groups based on the receptor-binding profile, incidence of extrapyramidal side effects and efficacy against negative symptoms: first-generation (also known as ‘typical’, ‘classical’ or ‘conventional’) antipsychotics such as haloperidol and chlorpromazine, and second-generation antipsychotics (also known as ‘atypical’ antipsychotics) such as clozapine, risperidone and aripiprazole [1, 2]. Therapeutic drug monitoring (TDM) refers to the quantification and interpretation of drug concentrations in blood to optimize pharmacotherapy [3, 4]. TDM has a long history in psychiatry, but routine TDM of antipsychotics has not yet been universally accepted as a standard clinical practice [3, 4]. In 2020, the American Society of Clinical Psychopharmacology and the Therapeutic Drug Monitoring Task Force of the German Association of Neuropsychopharmacology and Pharmacopsychiatry published a joint consensus statement with the aim to assist clinicians who regularly prescribe antipsychotics to effectively implement TDM of antipsychotics in their clinical practice [4]. The consensus statement provides four levels of recommendations regarding TDM for specific antipsychotics, their therapeutic reference range in blood and laboratory alert level (threshold level above which the risk for adverse drug reactions is expected to increase) [4]. Antipsychotics for which TDM is strongly recommended (level 1 recommendation) include clozapine, fluphenazine, haloperidol, olanzapine, perazine and perphenazine [4]. For these drugs, blood level within the therapeutic range is associated with favorable clinical outcomes in terms of efficacy, as well as safety and tolerability [4].