Antipsychotic polypharmacy- Evolution of prescribing patterns between admission and discharge of 5 Belgian hospitals

Objectives: Antipsychotic polypharmacy (APP) is common worldwide in the treatment of schizophrenia. We aimed at describing APP during psychiatric hospitalization in Belgium and comparing it to the European practice. Methods: We collected retrospective data from 5 hospitals in 2020-2021. The inclusion criteria were adult inpatients, hospitalized in a psychiatric unit, presenting with a diagnosis of schizophrenia or schizoaffective disorder, and taking an antipsychotic at admission. The proportion of patients on APP, antipsychotics’ exposition (i.e. prescribed daily dose (PDD)/defined daily dose (DDD) ratio) and excessive dosing (i.e. PDD/DDD>1,5), type, route, and cotreatment were compared between admission and discharge of hospitalization. Results: Of the 420 patients analyzed, 197 (46,9%) were on APP at admission and 244 (58,1%) at discharge (p<0,001). These figures largely exceed the European mean (23,0%; Gallego et al. (2012)). The antipsychotics’ exposition increased significantly from 1,70 at admission to 1,96 at discharge (p<0,001), so as the proportion of patients receiving excessive dosing (from 49,2% to 57,0% respectively; p<0,001). Compared to admission, more patients had a combination of a long-acting injectable with an oral antipsychotic at discharge (18,6% and 27,4%; p<0,001), and more were treated with a combination of a first-generation and an atypical antipsychotic (28,3% and 36,2%; p<0,001). Finally, more patients were on mood stabilizers (17,4% and 21,4%; p=0,019), benzodiazepines (45,2% and 56,7%; p<0,001), antiparkinsonian drugs (9,3% and 11,7%; p=0,06), or received an antipsychotic for insomnia (22,1% and 30,2%; p