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Thursday 28 June 2007

Risk of discontinuation of atypical antipsychotic agents in the treatment of schizophrenia.

By: Mullins CD, Obeidat NA, Cuffel BJ, Naradzay J, Loebel AD.

Schizophr Res 2007 Jun;(): [Epub ahead of print]

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).

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