Medicare Part D Cost Sharing and Antipsychotic Use in Two Medicare Advantage Plans

BACKGROUND/AIMS: The Affordable Care Act phases out the Medicare Part D coverage gap over the next decade; however, beneficiaries will continue to face substantial cost-sharing even after 2020. Higher cost-sharing has been associated with reductions in necessary drug use. Non-adherence to antipsychotics, a mainstay of schizophrenia treatment, is associated with worse clinical outcomes. We investigated the impact of Part D cost-sharing on antipsychotic spending and adherence for beneficiaries with schizophrenia, focusing on within-person cost-sharing increases associated with the gap. METHODS: We included Medicare Advantage (MA) beneficiaries enrolled in plans linked with an integrated delivery system (IDS, N=999) and non-integrated systems (non-IDS, N=3,878) who received 1+ inpatient or 2+ outpatient schizophrenia diagnoses during 2006–2007 and antipsychotics in 2006. We examined total and out-of-pocket antipsychotic spending and adherence based on the proportion of days covered (PDC) using Part D drug event data. We examined changes in monthly costs and adherence before and after beneficiaries reached the gap using within-person fixed effects models to account for unmeasured, time-stable confounders across comparison groups. RESULTS: Overall, 34% of subjects faced a gap in 2007; most remaining beneficiaries received low- income subsidies (LIS) that covered the gap. Among gap subjects, 45% (IDS) and 55% (non-IDS) reached the gap threshold of $2,400 in total drug spending. Monthly out-of-pocket spending increased substantially in both systems during vs. before the gap (IDS: $139 [$118 to $159]; non-IDS: $84 [$79 to $91]). Total monthly antipsychotic costs and adherence decreased after reaching the gap among non-IDS beneficiaries (costs: −$163 [−$179 to −$146]; adherence: −14.7 percentage points [−16.2 to −13.1]). Among IDS beneficiaries, changes in total costs and adherence pre- vs. post-gap were not significant (costs: −$82 [−$179 to $15]; adherence: 3.1 pp [−0.6 to 6.8]). For LIS beneficiaries with no gap, adherence did not decrease after reaching the gap spending threshold. DISCUSSION: Antipsychotic adherence decreased during the gap among non-IDS MA beneficiaries, but did not among IDS beneficiaries or among LIS recipients without a gap. Cost-related non- adherence to antipsychotics among beneficiaries with schizophrenia could result in adverse clinical outcomes. Work is needed to explore potential system-level characteristics that influence patients’ responses to cost-sharing. (August 2012)