Comparison of health services use associated with ziprasidone and olanzapine among schizophrenia and bipolar disorder patients in the USA

Abstract

Background and objectives: Ziprasidone is increasingly used for the treatment of schizophrenia and bipolar disorder. The purpose of this study was to compare healthcare costs and use associated with ziprasidone and olanzapine.

Methods: Ziprasidone and olanzapine treatment episodes of schizophrenia and bipolar disorder patients were identified in the 01/2007-12/2010 IMS LifeLink™ Database. The period of analysis for each episode has three components: 6 months prior to the episode initiation date (pre-episode period), 1 month immediately following the episode initiation date (initiation month), and up to 12 months after the end of the initiation month (follow-up period). Ordinary least squares regressions, general linear models, and two-part models were used to compare various types of costs (2007 US$) associated with the use of ziprasidone and olanzapine. Logistic regressions, Poisson regressions, and Hurdle models were used to compare the number of emergency department (ED) visits and hospitalizations associated with each drug.

Results: We identified 7,138 (46.93 %) ziprasidone episodes and 8,072 (53.07 %) olanzapine episodes, and found that patients using ziprasidone were significantly younger (41.50 vs. 45.38 years) and were significantly less likely to be male (29.81 vs. 44.21 %). Regression analysis showed no significant differences in total costs between the two drugs. However, ziprasidone was associated with significantly higher medication costs (US$232, p < 0.01) and outpatient costs (US$501, p < 0.05), yet lower ED costs (-US$73, p < 0.05). Ziprasidone was also associated with fewer ED visits (0.266, p < 0.001) and hospitalizations (1.117, p < 0.001).

Conclusions: Ziprasidone is associated with higher medication costs and outpatient costs than olanzapine; however, it reduces patients' use of ED and inpatient services.