Rising out-of-pocket costs for neurologic medications tied to poorer adherence

  • Neurology

  • von Susan London
  • Clinical Essentials
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Takeaway

  • Among patients with neuropathy and dementia, rising out-of-pocket costs for certain medications are associated with reduced adherence.

Why this matters

  • Nonadherence may compromise outcomes.

Key results

  • In multivariate instrumental variable analysis, each increase of US $50 (C$66, €46) in out-of-pocket costs conferred:
    • 9% lower adherence for patients with neuropathy on gabapentinoids (adjusted incidence rate ratio [IRR], 0.91; 95% CI, 0.89-0.93).
    • 12% lower adherence for patients with dementia on cholinesterase inhibitors (adjusted IRR, 0.88; 95% CI, 0.86-0.91).
  • No significant associations were seen for:
    • Patients with neuropathy on serotonin/norepinephrine reuptake inhibitors (adjusted IRR, 0.97; 95% CI, 0.88-1.08).
    • Patients with Parkinson's disease on dopamine agonists (adjusted IRR, 0.90; 95% CI, 0.81-1.00).

Study design

  • A retrospective cohort study of privately insured patients with claims in 2001-2016:
    • 52,249 patients with neuropathy on gabapentinoids,
    • 5246 patients with neuropathy on serotonin/norepinephrine reuptake inhibitors,
    • 19,820 patients with dementia on cholinesterase inhibitors, and
    • 3130 patients with Parkinson’s disease on dopamine agonists.
  • Main outcome: medication adherence (days supplied in first 6 months postdiagnosis).
  • Funding: American Academy of Neurology Health Services Research Subcommittee.

Limitations

  • Reliance on diagnosis codes.
  • Smaller sample sizes for some drug-disease combinations.
  • Inability to directly adjust for adverse events, measure nonadherence for first postdiagnosis prescription.
  • Assumption that patients took all medications supplied.
  • Unclear generalizability.