Levodopa dose maintenance or reduction in patients with Parkinson's disease transitioning to levodopa/carbidopa/entacapone

Background: Levodopa bioavailability is enhanced by adding entacapone. However, the optimal dose of levodopa while transitioning to levodopa/carbidopa/entacapone (LCE) in Parkinson's disease (PD) during the wearing-off period is unclear. Aims: The relative therapeutic efficacy and safety of different doses of levodopa were assessed when transitioning to the LCE combination for optimizing combined levodopa therapy. Materials and Methods: A randomized, multicenter, double-arm, open-label study was conducted in Korea. The patients were randomly assigned to either a maintained levodopa dose (Group 1, n = 66) or a reduced levodopa dose by 15-25% (Group 2, n = 41). Treatment efficacy, safety, and tolerability were assessed during an 8-week treatment period. Results: Eighty of the 107 (74.8%) participants completed the study (Group 1, n = 50; Group 2, n = 30). The patients' global impression of a change in scores indicated significant benefits of maintaining the levodopa dose (Group 1) compared to reducing the dose (Group 2). Although changes in the unified Parkinson's disease rating scale (UPDRS) scores, Hoehn and Yahr (H and Y) stages, and duration of ON, OFF and dyskinesia were not statistically different between the groups, an increased ON time and a reduced OFF time occurred in both the groups after LCE administration. Twenty-four participants (26.7%) experienced adverse events and 15 of them did not complete the study in the safety population (Group 1, n = 57; Group 2, n = 38). Significant drug-related withdrawal caused troublesome dyskinesia and aggravation of Parkinsonism in both Group 1 and Group 2, respectively. Conclusions: Direct transitioning to LCE, without levodopa dose reduction, is recommended in Asian patients with PD and wearing-off.