Effects of Adopting Preventive Drug Lists on Medication Costs and Disparities by Income Over 2 Years: A Natural Experiment for Translation in Diabetes (NEXT-D) Study

OBJECTIVE To examine the association between preventive drug lists (PDLs) and changes in medication costs among patients with diabetes insured in commercial health plans over 2 follow-up years. RESEARCH DESIGN AND METHODS We conducted a quasiexperimental study using the Optum deidentified Clinformatics Data Mart Database (January 2003 to December 2017). The intervention group included 5,582 patients with diabetes age 12–64 years switched by employers to PDL coverage; the control group included 5,582 matched patients whose employers offered no PDL. Outcomes included out-of-pocket costs, standardized costs, and 30-day fills for all medications because PDL-associated savings could be used to pay for medicines in other classes and for five therapeutic classes covered by the PDLs (oral diabetic medications, insulins, test strips, antihypertensive drugs, and lipid-lowering drugs). RESULTS Pre– to post–out-of-pocket spending for all medications declined by 29.7% in follow-up year 2 (95% CI −36.0, −23.4%) among PDL members relative to controls. Higher-income and lower-income PDL members experienced significant reductions in out-of-pocket spending for all medications in year 2 (30%) and for key therapeutic classes (range −23 to −67%). We found significant increases in use of key therapeutic classes in the overall population (range 8–15%) and in higher-income and lower-income PDL members (range 9–50%). CONCLUSIONS PDLs offer an effective strategy for employers and insurers to lower member cost sharing and encourage increased use of important medications to prevent or manage chronic illnesses. For patients with diabetes, especially those with lower incomes, PDL coverage resulted in substantial and persistent reductions in out-of-pocket medication costs, medication use increases, and some increased use of more expensive products.