PHP22: PATIENT ADHERENCE TO DRUG THERAPY IN A THREE-TIER COPAYMENT STRUCTURE

Abstract

BACKGROUND: The three-tier copayment plan is designed to reduce the cost of pharmacy benefits to the insurer or payer while maintaining patient choice. Because the patient pays a larger portion of the cost of middle- and high-tier drugs, some have argued that this plan design may adversely impact patient drug utilization for chronic medications. OBJECTIVE: To determine whether a three-tier copayment structure adversely affects patient drug utilization for middle- and upper-tier drugs for diabetes and depression. METHODS: We conducted a longitudinal, retrospective claims database study using claims data from a national pharmaceutical benefits management company. Claims for two chronic conditions, depression and oral diabetes, were examined for patients on three-tier copayment plans and for patients on an open formulary plan with the same copayment for every drug. Average rates of patient adherence, number of prescriptions filled, and days of therapy were calculated. RESULTS: There were statistically significant differences in rates of patient adherence, number of prescriptions filled, days of therapy, amount of copay, and payer costs among patients using drugs in the lower, middle, or upper tier of the three-tier structure. In addition, average patient adherence, number of prescriptions filled, and days of therapy did differ significantly for patients on an open formulary compared to patients on a three-tier copayment structure. These differences were largely a function of sample size, and may be of little practical utility.CONCLUSIONS: The larger patient copayment for medications in the middle and upper tiers of a three-tier copayment structure have only a minimal impact on drug utilization in the antidepressant and oral diabetes drug categories. Further research is needed to determine whether these findings would be replicated when applied to other therapeutic classes.