Comparison of long-term use of prolonged-release ropinirole and immediate-release dopamine agonists in an observational study in patients with Parkinson's disease

Purpose To estimate the risk of dyskinesia and impulse control disorders (ICDs) in patients with Parkinson's disease (PD) prescribed ropinirole prolonged-release (R-PR) compared to those prescribed immediate-release dopamine agonists (IR-DA) as monotherapy. Methods PD patients initiating R-PR or IR-DA as monotherapy between 2008 and 2013 were identified on the Clinical Practice Research Datalink. The cohorts were propensity score matched on a 1:1 basis. The incidence of dyskinesia and ICD in each treatment cohort and the incidence rate ratios were calculated. Adherence to medication and time to levodopa initiation were also evaluated. Results We identified 341 patients in each treatment cohort after propensity score matching. The baseline characteristics were generally comparable. Dyskinesia incidence in R-PR and IR-DA cohorts was 2.98 (95% CI: 0.74-11.9) and 3.93 (95% CI: 0.98-15.7) per 1000 person-years, respectively (incidence rate ratio of R-PR vs ID-DA: 0.76, 95% CI: 0.11-5.38). Less than five cases of ICD were identified and all occurred in the IR-DA cohort. The patients in the R-PR cohort remained on treatment for a significantly longer duration than those in the IR-DA cohort (682 days vs 444 days; P < .0001) and had greater adherence to the medication. The median time to levodopa initiation was 417 days (IQR: 205-736) in R-PR vs 297 days (IQR: 111-552) in IR-DA cohort. Conclusions The number of dyskinesia and ICD events was lower than expected, resulting in an underpowered study. A significantly longer persistence and greater adherence to medication was observed in patients receiving R-PR compared to IR-DA.