Levodopa response in early Parkinson's disease.

To further characterize the short-term levodopa response in early PD, we performed a retrospective analysis of the ELLDOPA study which randomized 361 early PD subjects to placebo, levodopa 150, 300, or 600 mg/day. We evaluated change in UPDRS motor scores (UPDRSm) from baseline to weeks 9 and 24, and identified changes in UPDRSm that best discriminated treatment with levodopa from placebo. Linear regressions were used to determine associations between baseline characteristics and changes in UPDRSm. Mean percent improvement in UPDRSm in levodopa-treated subjects was greater than that for placebo-treated subjects (27.4% vs. 5.8% at 9 weeks, P < 0.001 and 26.2% vs. 4.0% at 24 weeks, P < 0.001). UPDRSm change at 9 weeks ranged from -92.9% (improvement) to 85.7% (worsening) for levodopa and -86.7% to 160% for placebo, and at 24 weeks ranged from -100.0% to 242.9% for levodopa and -87.5% to 112.5% for placebo. UPDRSm improvements of 22.0% at 9 weeks and 23.8% at 24 weeks best discriminated treatment with levodopa 300 mg/day (a common initial maintenance dosage in clinical practice) from placebo. Significant associations were not observed between baseline subject characteristics and magnitude of response from baseline to week 24. We conclude that although levodopa treatment significantly improved PD signs when compared with placebo, there was a wide range and considerable overlap in clinical responses to levodopa and placebo. A substantial proportion of subjects with early PD did not experience a robust response to levodopa. An improvement in UPDRSm of approximately 22% best discriminated levodopa treatment from placebo.