Trends in quetiapine use and non-fatal quetiapine-related ambulance attendances

Introduction and aims: Concern about the non-medical use of quetiapine and related acute harms is growing. Case series cite quetiapine as a potential drug of misuse, while recent research questions its relative safety in comparison with other atypical antipsychotic preparations. This paper explores population-level patterns of quetiapine-related ambulance attendances over time, identifying associated risk factors and potential subpopulations at-risk of acute harms.

Design and methods: A retrospective analysis of quetiapine-, olanzapine- and risperidone-related ambulance attendances in metropolitan Melbourne and prescription data in Victoria, Australia. Trends in ambulance attendance and prescription rates, attendance characteristics, and associated risk factors were explored from 2001 to 2010.

Results: Quetiapine was consistently associated with substantially higher rates of ambulance attendances relative to prescription availability than olanzapine or risperidone. Quetiapine prescribing rates increased at a significantly greater magnitude than olanzapine or risperidone, leading to substantial increases in quetiapine attendances by population. Quetiapine-related attendances were associated with concurrent heroin and opioid replacement therapy toxicity, history of heroin and alcohol misuse, mood disorders, low Glasgow Coma Scale and women.

Discussion and conclusions: Trends in quetiapine-related ambulance attendances indicate rising community-level harms and greater harm relative to other atypical antipsychotics, while prescription patterns suggest increasing quetiapine availability. The association of quetiapine-related attendances with concurrent heroin and opioid replacement therapy toxicity as well as previous heroin and alcohol misuse suggest illicit and poly-drug users are a subpopulation at greater risk of quetiapine-related harms, consistent with emerging evidence of the use, misuse and diversion of quetiapine.