Risk of discontinuation of atypical antipsychotic agents in the treatment of schizophrenia
Received 15 November 2006; received in revised form 25 April 2007; accepted 26 April 2007. published online 28 June 2007.
Abstract
Objectives
To compare discontinuation rates of atypical antipsychotic agents in patients with schizophrenia.
Method
Adult Maryland Medicaid patients with schizophrenia were categorized based on initial atypical antipsychotic drug received: aripiprazole (n=446); olanzapine (n=1705); quetiapine (n=1467); risperidone (n=1580); and ziprasidone (n=700). Discontinuation was measured using refill patterns, allowing 14-day gaps between refill dates. Using olanzapine as the reference drug, the hazard of discontinuation within the first year of follow-up was compared across atypicals using Cox proportional hazard models adjusted for demographic and clinical covariates. Sensitivity analysis tested the robustness of results by using different definitions of the index date.
Results
At one-year follow-up, most patients discontinued their antipsychotic medication (90.4% adjusted mean discontinuation). The hazard ratio (HR) for discontinuing therapy in patients starting treatment on aripiprazole, risperidone, or ziprasidone was not significantly different from olanzapine [HR 1.047, 0.973 and 0.990, respectively]. Quetiapine was associated with significantly higher hazard of discontinuation [HR 1.130] than olanzapine. Covariates associated with significantly lower discontinuation were being male [HR 0.899], older age [HR 0.997] and being on concurrent medication when initiating therapy [HR 0.225]; having a previous hospitalization was associated with significantly higher discontinuation hazard [HR 1.276]. Results were robust in the sensitivity analysis.
Conclusions
Discontinuation rates were high at one-year follow-up and did not differ significantly for patients on aripiprazole, olanzapine, risperidone, or ziprasidone. The higher hazard of discontinuation associated with quetiapine when compared to olanzapine is consistent with that observed in Phase I of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE).
ABSTRACT