Comparing the treatment patterns of patients with schizophrenia treated with olanzapine and quetiapine in the Pennsylvania Medicaid population

OBJECTIVE: Compare treatment patterns for patients with schizophrenia treated with olanzapine versus quetiapine in the Pennsylvania Medicaid population. METHODS: Patients (18-64 years) with a diagnosis of schizophrenia (ICD-9-CM: 295.xx) and treated with olanzapine or quetiapine were identified from the Pennsylvania Medicaid claims database (1999-2003). Patients were continuously enrolled in the 12-month pre- and 12-month post-initiation periods. To control for selection bias, propensity score method with optimal matching algorithm was used to match patients from the two treatment groups. The key study outcomes including rates of augmentation, polypharmacy, discontinuation, and switching were analyzed using Kaplan-Meier survival analysis. Medication possession ratio and use of concurrent psychotropic drugs were also compared between the two groups. RESULTS: A total of 2321 quetiapine and 6929 olanzapine patients were identified. In all, 2321 pairs of patients were matched between the two groups and they had similar baseline characteristics. Over the 12-month study period, olanzapine patients had a better medication adherence (0.47 vs. 0.43; p < 0.0001), and were less likely to use other psychotropic medications concomitantly (all p < 0.05). Olanzapine patients had a significantly lower risk of augmentation and polypharmacy with other antipsychotics. The 6-month augmentation rates with antipsychotics were 12.9% and 16.7% for olanzapine and quetiapine, respectively (p < 0.05); the polypharmacy rates with any antipsychotics were 12.5% and 18.6% for olanzapine and quetiapine, respectively (p < 0.001). No significant differences were observed for discontinuation and switching between the two treatment groups. Sensitivity analysis with a 60-day minimum monotherapy requirement showed similar results. LIMITATIONS: This study's limitations include the analysis of a single Medicaid state, which may limit the generalizability to the entire Medicaid population with schizophrenia or to all patients with schizophrenia. CONCLUSION: This large Medicaid claims database analysis showed that olanzapine patients were significantly more compliant to treatment and less likely to augment or have polypharmacy with antipsychotics during the course of treatment compared to quetiapine patients.