Association of out-of-pocket costs on adherence to common neurologic medications

Objective To determine the association between out-of-pocket costs and medication adherence in 3 common neurologic diseases. Methods Utilizing privately insured claims from 2001 to 2016, we identified patients with incident neuropathy, dementia, or Parkinson disease (PD). We selected patients who were prescribed medications with similar efficacy and tolerability, but differential out-of-pocket costs (neuropathy with gabapentinoids or mixed serotonin/norepinephrine reuptake inhibitors [SNRIs], dementia with cholinesterase inhibitors, PD with dopamine agonists). Medication adherence was defined as the number of days supplied in the first 6 months. Instrumental variable analysis was used to estimate the association of out-of-pocket costs and other patient factors on medication adherence. Results We identified 52,249 patients with neuropathy on gabapentinoids, 5,246 patients with neuropathy on SNRIs, 19,820 patients with dementia on cholinesterase inhibitors, and 3,130 patients with PD on dopamine agonists. Increasing out-of-pocket costs by $50 was associated with significantly lower medication adherence for patients with neuropathy on gabapentinoids (adjusted incidence rate ratio [IRR] 0.91, 0.89–0.93) and dementia (adjusted IRR 0.88, 0.86–0.91). Increased out-of-pocket costs for patients with neuropathy on SNRIs (adjusted IRR 0.97, 0.88–1.08) and patients with PD (adjusted IRR 0.90, 0.81–1.00) were not significantly associated with medication adherence. Minority populations had lower adherence with gabapentinoids and cholinesterase inhibitors compared to white patients. Conclusions Higher out-of-pocket costs were associated with lower medication adherence in 3 common neurologic conditions. When prescribing medications, physicians should consider these costs in order to increase adherence, especially as out-of-pocket costs continue to rise. Racial/ethnic disparities were also observed; therefore, minority populations should receive additional focus in future intervention efforts to improve adherence.