Increase in out-of-pocket costs associated with lower adherence to neurologic medications

As out-of-pocket costs go up for drugs for the neurologic disorders Alzheimer's disease, peripheral neuropathy and Parkinson's disease, people are less likely to take the drugs as often as their doctors prescribed, according to a study funded by the American Academy of Neurology and published in the February 19, 2020, online issue of Neurology^®, the medical journal of the American Academy of Neurology.

These results are concerning, especially as we've seen the cost of prescription drugs continue to rise and an increasing amount of the cost being shifted to patients through out-of-pocket costs. Of course, if people do not follow their prescriptions correctly, they are less likely to benefit from the drug and see improvements in their condition, possibly leading to complications and higher costs later."

Brian C. Callaghan, MD, MS, study author from University of Michigan in Ann Arbor and a Fellow of the American Academy of Neurology

For the study, researchers examined a private insurance claims database for new cases of Alzheimer's disease or other dementia, Parkinson's disease, and peripheral neuropathy over a 15-year period. Peripheral neuropathy is a common condition in which the peripheral nerves become damaged, causing weakness, numbness and pain, typically in the hands and feet. All of these conditions have drugs available that have similar effectiveness and side effects, but different out-of-pocket costs.

For example, the average out-of-pocket cost in 2016 for a 30-day supply of the Alzheimer's drug rivastigmine was $79.30, compared to $3.10 for the drug donepezil. For the peripheral neuropathy drug pregabalin the cost was $65.70, compared to $8.40 for gabapentin. For Parkinson's, the drug pramipexole cost $35.90, compared to $12.40 for the drug ropinirole.

The researchers then looked at how closely the people followed their prescriptions by seeing how many days' worth of the drug were supplied to each person within the first six months.

The study involved 19,820 people with dementia who were taking the study drugs; 52,249 people with neuropathy who were taking the class of drugs called gabapentinoids, which include pregabalin and gabapentin; 5,246 people with neuropathy who were taking the class of drugs called mixed serotonin-norepinephrine reuptake inhibitors (SNRIs), which included duloxetine and venlafaxine; and 3,130 people with Parkinson's who were taking the study drugs.

The study found that increases in out-of-pocket costs by $50 were associated with lower adherence to prescriptions. For Alzheimer's disease, a $50 increase in out-of-pocket costs was associated with a 12-percent decrease in the medication possession ratio, which is the percentage of time a person has access to medication. For example, in 2015, when the cost of the drug donepezil was about $3 for a 30-day supply, people filled their prescriptions about 70 percent of the time; this is compared to the drug rivastigmine, which cost about $100 for a 30-day supply at that time and people filled their prescriptions about 45 percent of the time.

For peripheral neuropathy, a $50 increase in out-of-pocket costs for the gabapentinoid drugs was associated with a 9-percent decrease in the medication possession ratio.

The researchers also found that Asian, black and Latino people had larger drops in medication adherence rates than white people for equivalent increases in out-of-pocket costs.

"New approaches to increase medication adherence for these population groups is critically important to reducing health care disparities," Callaghan said.

Callaghan also noted that people with Alzheimer's disease and neuropathy often have other conditions that require medication, so the effect of out-of-pocket drug costs may be magnified.

"Out-of-pocket costs have risen to the point where systematic changes are needed," said James C. Stevens, MD, FAAN, President of the American Academy of Neurology. "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. 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."

A limitation of the study was that researchers were not able to measure how many people never filled their first prescription of a drug, which could be related to out-of-pocket costs. In addition, the study looked only at people with private insurance, so the results may not apply to other populations.