PREPARED: Comparison of prolonged and immediate release ropinirole in advanced Parkinson's disease.

Background: PREPARED was a randomized, parallel-group, double-blind, multicenter study to evaluate the efficacy of adjunctive ropinirole prolonged release (PR) versus immediate release (IR) in patients with advanced Parkinson's disease (PD).

Methods: Patients received once-daily PR (2-24 mg/d; n = 177) or three-times-daily IR (0.75-24 mg/d; n = 173) for 24 weeks. The primary endpoint was the proportion of patients maintaining ≥ 20% reduction from baseline in "off" time over two consecutive visits at Week 24 last observation carried forward (LOCF).

Results: At Week 24 LOCF, PR significantly increased the proportion of patients maintaining ≥ 20% reduction in "off" time versus IR (adjusted odds ratio: 1.82; 95% CI: 1.16, 2.86; P = 0.009). Mean (SD) doses at Week 24 LOCF were: PR, 18.6 (6.5) mg/d; IR, 10.4 (6.4) mg/d; mean (SD) reductions from baseline in levodopa (L-dopa) dose were -162 (226) mg and -113 (138) mg, respectively. Adverse events (AEs) were reported by 72% of patients in the PR group and 61% in the IR group; 12% and 9% of patients, respectively, withdrew from the study due to an AE, and 6% and 5%, respectively, reported serious AEs.

Conclusions: Adjunctive PR provided a significantly greater improvement in symptom control in terms of the odds of achieving ≥ 20% maintained reduction in time spent "off" compared with IR. Interpretation may be confounded by the higher doses of PR versus IR that were achieved, in combination with lower doses of L-dopa by the study end. Despite dosing differences, the PR titration regimen was generally well tolerated, with an AE profile similar to that of IR.