The influence of a statin therapeutic interchange on economic and health care utilization outcomes from the perspective of a managed Medicaid insurer

Background. Health care administrators are using various mechanisms including therapeutic interchange (TI) to control rising pharmacy expenditure. Previous research has attempted to determine the influence of TI on the health care system, but has suffered from limited generalizability of the patient populations, weak study designs, inadequate statistical analyses, and limited economic outcomes.; Purpose. The purpose of this study was to assess the economic and clinical utilization of services following a statin therapeutic interchange from the perspective of a third party payer.; Methodology. Data were obtained from a geographically diverse managed Medicaid population. Continuously enrolled patients who had a minimum of three atorvastatin claims during a 6-month enrollment phase and were converted from atorvastatin to another statin between April 1 st, 2003 and July 31st, 2003 were enrolled in the study. A multivariate panel analytic technique was used to analyze ambulatory visits, ambulatory expenditure, statin expenditure, and total health care expenditure during the pre-period versus the post-therapeutic interchange period. A total of twelve 30-day panels were created during the pre-therapeutic interchange period and twelve 30-day panels were created during the post-therapeutic interchange period.; Results. A total of 3,636 patients met the study inclusion criteria. Multivariate models were used to assess change in utilization and expenditure. Ambulatory utilization increased by 1.10 to 1.30 (p < 0.0001) visits for the one-year following the therapeutic interchange; however no statistically significant differences in total ambulatory expenditures were documented. After adjusting for fluctuating utilization patterns resulting from the study design both statin expenditure (without consideration of product rebates) and total expenditure decreased by 22% (p < 0.0001) following the therapeutic interchange.; Conclusion. Despite a slight increase in ambulatory visits, total expenditure decreased following the statin TI among therapeutically stable statin users within a managed Medicaid population. These results are driven primarily by the large reduction in statin expenditure relative to ambulatory visit expenditure.