Factors predicting high-dose and combined antipsychotic prescribing in New Zealand: High-dose antipsychotic prescribing

Abstract

ObjectiveGuidelines recommend using antipsychotic monotherapy at the lowest effective dose, however high-dose and antipsychotic polypharmacy prescribing (APP) remain commonplace. The aim of this study was to determine the prevalence and patterns of high-dose antipsychotic prescribing and APP among mental health service users in New Zealand (NZ). MethodsA retrospective audit of service users discharged from inpatient (n=657), or registered with community (n=1560), mental health services at Auckland District Health Board was undertaken. Case notes were reviewed and data on demographics, antipsychotic routes and doses were collected. Outcomes measures included: frequency of total high-dose prescribing, high-dose monotherapy, APP, high-dose APP, and factors associated with these prescribing practices. Logistic regression models were used to examine the relationships between explanatory and outcome variables. ResultsOf the service users prescribed an antipsychotic (n = 2217), 14% were prescribed a high-dose antipsychotic. The frequency of high-dose monotherapy, APP, and high-dose APP was 3%, 26% and 11%, respectively. Being male, Māori, on compulsory treatment, having a schizophrenia diagnosis, or being prescribed polypharmacy were associated with high-dose antipsychotics. Olanzapine was most frequently prescribed in both high dosing (55%) and APP (40%). ConclusionsThere is a high prevalence of high-dose prescribing and APP in this NZ setting.