Higher Neuropathy, Dementia Drug Costs Lead to Lower Adherence

Higher out-of-pocket costs were linked with lower medication adherence among patients with peripheral neuropathy or dementia, an analysis of private insurance claims showed.

Among neuropathy patients, a $50 increase in out-of-pocket costs for gabapentinoids was associated with a 9% decrease in adherence, reported Brian Callaghan, MD, MS, of the University of Michigan in Ann Arbor, and colleagues.

Similarly, a $50 increase in out-of-pocket costs was tied to a 12% drop in medication adherence of cholinesterase inhibitors for dementia, they reported in Neurology.

“Out-of-pocket costs can lead to a predictable drop in taking medications prescribed by physicians,” Callaghan said. While previous studies focused on very expensive drugs like disease-modifying therapies for multiple sclerosis, “we were able to show that even small changes in out-pocket-costs affect medication adherence,” Callaghan told MedPage Today.

Not only are out-of-pocket drug costs rising, but high-deductible health plans are more prevalent, he added.

“The predictable decrease in medication adherence with even small changes in out-of-pocket costs likely has important implications for patient care,” he said. “This is a new problem in the last 10 years that likely requires new healthcare policy solutions.”

In a statement, James Stevens, MD, president of the American Academy of Neurology, which supported the study, echoed that conclusion. “Out-of-pocket costs have risen to the point where systematic changes are needed,” he said.

“These changes could include legislative action to place a cap on out-of-pocket costs, which the American Academy of Neurology is advocating for in Washington, D.C.,” Stevens pointed out. “Another change could be to provide neurologists with access to information on drugs costs so that when they meet with patients to make treatment decisions, they can help to minimize the financial burden.”

In their analysis, Callaghan and colleagues looked at private insurance claims for patients with incident neuropathy, dementia, or Parkinson’s disease in Clinformatics Data Mart records from 2001 to 2016. They defined medication adherence as the number of days supplied in the first 6 months, and medication possession ratio as the percentage of time a patient has access to medication.

The researchers selected patients who had been prescribed medications with similar efficacy and tolerability, but different out-of-pocket costs.

• For neuropathy, they looked at people taking gabapentinoids (7,648 on pregabalin and 44,601 on gabapentin; average age 65) and 5,246 taking SNRIs (average age 60): 3,747 taking duloxetine (Cymbalta) and 1,499 taking venlafaxine (Effexor)
• For dementia, they assessed people with an average age of 79 taking cholinesterase inhibitors: 1,141 patients on galantamine (Razadyne) or rivastigmine (Exelon), and 18,679 patients on donepezil (Aricept)
• For Parkinson’s, they studied patients with an average age of 71 who were taking one of two dopamine agonists: 1,813 people on ropinirole (Requip) and 1,510 people on pramipexole (Mirapex)

In previous work, the authors found that the average 30-day supply of out-of-pocket costs were different in 2016 for each of the drugs compared:

• For neuropathy drugs, 30-day costs were $65.70 for pregabalin, $8.40 for gabapentin, $32.10 for duloxetine, and $10.00 for venlafaxine
• For dementia drugs, monthly out-of-pocket costs were $79.30 for rivastigmine, $59.40 for galantamine, and $3.10 for donepezil
• For Parkinson’s drugs, 30-day costs were $35.90 for pramipexole and $12.40 for ropinirole

Increasing out-of-pocket costs by $50 was associated with significantly lower medication adherence for neuropathy patients on gabapentinoids (adjusted incidence rate ratio of 0.91, 95% CI 0.89-0.93) and for dementia patients on cholinesterase inhibitors (adjusted IRR 0.88, 95% CI 0.86-0.91). Compared with white patients, patients from minority populations had lower adherence with gabapentinoids and cholinesterase inhibitors.

Medication possession ratios varied depending on the cost of the drug. In 2015, for example, dementia patients filled their prescriptions for donepezil about 70% of the time and for more expensive rivastigmine about 45% of the time.

Higher out-of-pocket costs for neuropathy patients on SNRIs (adjusted IRR 0.97, 95% CI 0.88-1.08) and for patients with Parkinson’s disease on dopamine agonists (IRR 0.90, 95% CI 0.81–1.00) were not significantly tied to adherence.

This study had several limitations, Callaghan and colleagues noted. Researchers could not determine how many people never filled their first prescription of a drug; there may be reasons besides cost that patients do not start, or stop taking, drugs. Sample sizes for some drugs were small. In addition, the study looked only at people with private insurance and results may not apply to other populations.