- 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.
- 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).
- 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.
- 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.