To examine adherence and discontinuation to oral anti-Parkinson drug regimens in Medicare enrollees with advanced Parkinson’s disease (APD).

Medication regimens of patients with APD can often become complex due to polypharmacy and frequent dosing, contributing to increased risk of medication non-adherence. Yet, little is known about real-world compliance with high dose regimens in APD.

This was a retrospective analysis of 2011-2013 100% Medicare claims data on patients with Parkinson’s disease (ICD-9-CM:332.0) and a prescription claim for levodopa in 2012. Incident patients with APD were identified as those with 30-day average levodopa equivalent dose (LED) > 1,000 mg in 2012, without similar levels of LED in the prior 12 months. Patients were required to have 12 month enrollment pre- and post- index date (i.e. first 30-day period meeting the LED cut-off). Adherence (proportion of days covered > 0.80) and discontinuation (90 consecutive days not receiving dose) were measured over a 12-month post-index period. Both outcomes were measured across multiple dose levels. Logistic regressions examined factors associated with these outcomes.

For patients with APD (n=9,405), adherence to treatment of LED regimens of >1,000 mg/day, >800 mg/day, >500 mg/day, and any dosage was 5%, 20%, 56%, and 76%, and discontinuation rates were 75%, 53%, 19%, and 10%, respectively.  Factors impacting adherence included race, sex, syncope, and anxiety. Sensitivity analyses adjusting the definitions of APD, adherence, and discontinuation showed consistent findings.