Patient characteristics and the likelihood of initiation on olanzapine or risperidone among patients with schizophrenia

Boston University, Boston, Massachusetts, United States
Schizophrenia Research (Impact Factor: 3.92). 10/2005; 77(2-3):167-77. DOI: 10.1016/j.schres.2005.04.005
Source: PubMed


Although pharmacologic treatments are available for patients with schizophrenia, little is known about how prescription patterns of atypical antipsychotic agents are related to patient characteristics. In this study, we examined the association between patient characteristics and the likelihood of being initiated on olanzapine or risperidone, two of the most frequently prescribed atypical agents for schizophrenia. We selected patients who were diagnosed with schizophrenia or schizoaffective disorder based on > or = 1 inpatient or > or = 2 outpatient ICD-9-CM codes (> or = 7 days apart) between 7/1/98 and 6/30/99 from the Veterans Health Administration (VA). We classified patients into one of three types of initiation: (a) not on olanzapine or risperidone, (b) not on any atypical agents, or (c) not on any antipsychotic agents for 6 months, and then subsequently being prescribed the target drugs. Using logistic regression, we examined whether the odds ratio of being initiated on olanzapine versus risperidone are related to patient sociodemographic and clinical characteristics. Compared to risperidone initiators, olanzapine initiators used more drugs for psychiatric conditions (including antiparkinsonian agents, typical antipsychotics, and mood stabilizers) than risperidone initiators. On the other hand, risperidone initiators had more medical comorbidities and more non-psychiatric hospitalizations. Olanzapine and risperidone appear to be prescribed to patients with different characteristics. Initiation of risperidone was more common among patients who presented with more medical comorbid conditions, whereas initiation of olanzapine was more common among patient who presented with more mental comorbid conditions. Future research needs to determine the reasons for those differences.

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    • "However, considering the inappropriateness of the conventional approach in measuring medication adherence as well as the limitations of the present study, more research is needed to examine the extent to which adjunctive use of other agents, a common practice among patients with schizophrenia,28 dose of treatment, and stage of illness will influence levels of treatment adherence. Future research should also assess the impact of poor treatment adherence on a wide spectrum of patient outcomes.29 A more comprehensive assessment using appropriate analytic methods should provide physicians with a better knowledge about treatment adherence associated with different antipsychotic agents and help them make prescription choices that will ultimately improve the care of schizophrenia. "
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    ABSTRACT: Background: Although clinical trials have demonstrated the efficacy of atypical antipsychotic agents in reducing symptoms of schizophrenia, the likelihood of sustaining control of schizophrenic symptoms may depend on treatment persistence. Objective: In this study, we compared treatment persistence between patients who were initiated on risperidone or olanzapine, the two most widely prescribed atypical antipsychotic agents. Method: We identified patients with schizophrenia by ICD-9-CM codes (≥1 inpatient or ≥2 outpatient ICD-9-CM codes ≥7 days apart) between 1 July 1998 and 30 June 1999. We further selected those who were prescribed the target drug during 1 April 1999 through 31 March 2000 provided that they were not on any antipsychotic agents during the prior 6 months. Using event history analysis, we compared the treatment persistence in terms of hazard ratio between olanzapine and risperidone initiators, adjusting for patient's sociodemographic and clinical characteristics. Results: Following the initiation of the target drug, more patients switched from risperidone to olanzapine than vice versa. However, among patients with schizophrenia who had comorbid diabetes, there were more patients who made a switch from olanzapine to risperidone; whereas among those who used anxiolytics, there were more patients who switched from risperidone to olanzapine. Finally, olanzapine initiators had decreased hazards of discontinuation by 14% (unadjusted; P < 0·001) and 12% (adjusted; P = 0·002), respectively, than risperidone initiators. Conclusions: Compared with risperidone, olanzapine seems to be better tolerated by patients as indicated by better treatment persistence. As such, initiation of olanzapine may increase the likelihood of sustaining control of symptoms of schizophrenia. Future research needs to provide a more comprehensive assessment of treatment persistence by considering other antipsychotic agents in the study and developing models to assess treatment persistence and switching as two interdependent competing risks.
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