Effects of a 3-Tier Pharmacy Benefit Design on the Prescription Purchasing Behavior of Individuals With Chronic Disease.

Abstract

To evaluate the impact of 3-tier (copayment) pharmacy benefit structures on medication utilization behavior. A pretest-posttest quasi-experimental design was employed. Chronic disease sufferers (N=8,132) from a health plan were classified into the following groups: (a) 2-tier copayment moving to a 3-tier structure, ("converting" group), (b) 2-tier staying in a 2-tier structure and, (c) 3-tier staying in a 3-tier structure. The latter 2 were "comparison" groups. Two 7-month time periods were determined: the "preperiod" (June through December 2000) and the "postperiod" (January through July 2001) for a change in pharmacy benefit structure. Pharmacy claims data were used for data collection. Statistical analyses included bivariate tests to evaluate predifferences and postdifferences across study groups. Maximum likelihood estimates from a repeated measures model were used to examine changes in formulary compliance and generic use rates. Discontinuation of nonformulary medications was evaluated using logistic regression. Controlling for demographics, number of comorbidities, disease state, and pharmacy benefit structure, the formulary compliance rate increased by 5.6% for the converting group. No significant increases were seen for the comparison groups. Generic use rates increased by 6 to 8 absolute percentage points for all groups (3.3% to 4.9 % adjusted rates). Converting group members were 1.76 times more likely to discontinue their nonformulary medication than those in the 2-tier comparison group and 1.49 times more likely than those in the 3-tier comparison group. These findings suggest that shifting individuals from a 2-tier to a 3-tier drug benefit copayment structure resulted in changes in medication utilization. Decision makers need to balance these changes with the potential dissatisfaction that members may express in paying higher copayments. Funding for this research was provided by Merck and Company through the Academic Medicine and Managed Care Forum and was obtained by authors Kavita V. Nair, Robert J. Valuck, Pamela Wolfe, Julie M. Ganther, and Marianne M. McCollum. Nair served as principal author of the study. Study concept and design was contributed by Nair, Valuck, Wolfe, Ganther, McCollum, and author Sonya J. Lewis. Analysis and interpretation of data and drafting of the manuscript were primarily the work of Nair and Wolfe, and all authors contributed to the critical revision of the manuscript. Statistical expertise was contributed by Wolfe. Administrative, technical, and/or material support was provided by Mark Enders.