No Difference on Adherence Between Immediate-Release Versus Extended-Release Dopamine Agonists in Uninsured Subjects with Parkinson's Disease

Background: Pharmacological management of subjects with Parkinson's disease (PD) is complex. Regardless of drug selection, adherence is one of the main concerns. Nonadherence is associated with poor symptomatic control and low quality of life. In general, adherence to once-a-day formulations is thought to be better in comparison to 3-times-daily dosing. Methods: A cross-sectional study was carried out. Consecutive uninsured subjects diagnosed with PD were treated either with an immediate-or extended-release dopamine agonist formulation. Clinical and demographic data were collected. Subjects were assessed using the International Parkinson and Movement Disorder Society UPDRS. Adherence was evaluated using the Morisky-Green test (MGT). Results: A total of 314 (175 males and 139 females) subjects with PD were included. In regard to treatment, 188 (59.9%) were on an immediate-release dopamine agonist and 126 (40.1%) on an extended-release dopamine agonist. According to the MGT, 21 (6.7%) subjects were classified as nonadherent, 273 (86.9%) with a low adherence, and only 20 (6.4%) were considered with high adherence. Dopamine agonist levodopa equivalent daily dose was higher in the extended-release group (296.6 +/- 112.4 vs. 231.3 +/- 133.4; P = 0.011); also, these subjects had more years of formal education (12.3 +/- 5.2 vs. 9.5 +/- 5.2; P = 0.630). No difference in adherence levels was found (P = 0.802) between subjects treated with an immediate-release dopamine agonist and those receiving an extended-release formulation. Conclusions: Overall adherence in subjects with PD is low. Use of an extended-release over an immediate-release dopamine agonist formulation in this study population is not associated with a better adherence.