Association Between Cost-Saving Prescription Policy Changes and Adherence to Chronic Disease Medications: an Observational Study

Abstract

Background: Pharmacy benefit design is one tool for improving access and adherence to medications for the management of chronic disease.

Objective: We assessed the effects of pharmacy benefit design programs, including a change in pharmacy benefit manager (PBM), institution of a prescription out-of-pocket maximum, and a mandated switch to 90 days' medication supply, on adherence to chronic disease medications over time.

Design: We used a difference-in-differences design to assess changes in adherence to chronic disease medications after the transition to new prescription policies.

Subjects: We utilized claims data from adults aged 18-64, on ≥ 1 medication for chronic disease, whose insurer instituted the prescription policies (intervention group) and a propensity score-matched comparison group from the same region.

Main measures: The outcome of interest was adherence to chronic disease medications measured by proportion of days covered (PDC) using pharmacy claims.

Key results: There were 13,798 individuals in each group after propensity score matching. Compared to the matched control group, adherence in the intervention group decreased in the first quarter of 2015 and then increased back to pre-intervention trends. Specifically, the change in adherence compared to the last quarter of 2014 in the intervention group versus controls was - 3.6 percentage points (pp) in 2015 Q1 (p < 0.001), 0.65 pp in Q2 (p = 0.024), 1.1 pp in Q3 (p < 0.001), and 1.4 pp in Q4 (p < 0.001).

Conclusions: In this cohort of commercially insured adults on medications for chronic disease, a change in PBM accompanied by a prescription out-of-pocket maximum and change to 90 days' supply was associated with short-term disruptions in adherence followed by return to pre-intervention trends. A small improvement in adherence over the year of follow-up may not be clinically significant. These findings have important implications for employers, insurers, or health systems wishing to utilize pharmacy benefit design to improve management of chronic disease.

Figure 1

A) Unadjusted adherence to chronic disease medications among MGB plan members and matched controls over time and B) the unadjusted difference in adherence between the groups.