Novel Type 2 Diabetes Medication Access and Effect of Patient Cost Sharing

BACKGROUND: Although drug formulary restrictions may reduce use of prescription medication and pharmacy costs, the effect of patient cost sharing on medication adherence and health care utilization and cost is unclear. OBJECTIVE: To evaluate the relationship between patient cost sharing for novel type 2 diabetes mellitus (T2DM) medications and medication adherence, persistence, and health care utilization and cost. METHODS: This retrospective study used medical and pharmacy claims linked to pharmacy benefit plan design data. Patients with T2DM were identified via ICD-9-CM codes (medical claims), outpatient prescription fills (pharmacy claims), and pharmacy benefit design information. Patients with T2DM treated with novel T2DM medications (DPP4 or GLP-1) were enrolled in plans with fixed or coinsurance medication copayment structures and followed for 12-48 months. Endpoints included medication persistence and adherence and total all-cause health care cost. Multivariable regression analysis estimated the effect of benefit design parameters, adjusting for baseline patient characteristics. RESULTS: The integrated database included 36,475 patients with T2DM. The majority (83.1%) had fixed copayment plans, and 3-tier plans were common (93.1%). Higher third-tier copayment was associated with poorer medication adherence and persistence but not total health care cost during follow-up. A $10 higher third-tier copayment was associated with 11% greater risk of novel T2DM medication discontinuation and 3% lower adherence. A comparison of patients with fixed versus coinsurance plans found that fixed plans were associated with higher adjusted persistence and total all-cause health care costs. CONCLUSIONS: Higher medication copayment amounts were associated with lower patient medication adherence and persistence in T2DM but not total health care costs, as health plan costs decreased while patient out-of-pocket costs increased. We observed higher total all-cause health care costs among T2DM patients with a fixed copay (vs. coinsurance) pharmacy benefit. Additional research incorporating plan design information is needed to further examine this finding.