Relationships between antiparkinson medication nonadherence, regimen modifications, and healthcare utilization and...

To examine 1) the effect of prior antiparkinson drug (APD) nonadherence on subsequent APD regimen modifications; and 2) the influence of modifications on healthcare utilization and costs by patients with Parkinson's disease (PD).

This retrospective cohort study included 7052 PD patients with ≥2 APD prescriptions who initiated a modification of APD regimens in 2007. Modification was assessed as changing from one APD to another and/or adding a new APD to an existing regimen. Nonadherence was measured using Medication Possession Ratio <0.8. Discrete-time survival analyses were used to estimate the effect of prior nonadherent behavior on initiating APD modifications. Generalized linear models were used to estimate the effect of initiating medication modifications on subsequent 3-month medical use and costs.

Initiation of APD modifications in any given month was higher among patients who were nonadherent to APDs in the preceding month (adjusted hazard ratio [HR] = 1.23), compared to their adherent counterparts. Modifications significantly predicted higher risk of all-cause and PD-related hospitalizations (adjusted relative risk [RR] = 1.22 and 1.83, respectively), home health agency utilization (RR = 1.18 and 1.52), and use of physician services (RR = 1.14 and 1.41), as well as higher total all-cause healthcare expenditures (mean = $1064) in any given 3-month interval.

Prior nonadherence to APDs might influence initiation of APD modification. APD modifications were associated with increased health care utilization and expenditures, with the caveats that indications of modifications and disease severity may still play roles. Prescribers should consider patients' medication adherence when changing APD regimens to lower the costs of medical services.