[Levodopa loading test as an early marker of Parkinson's disease]

We report levodopa absorption profile in 8 patients with early stage Parkinson's disease(PD) and in 8 age-matched normal control(NC) subjects; the gastric emptying time(GET) was also studied simultaneously. Patients with PD showed a significantly higher peak plasma levodopa concentration, however, no significant difference was present in the GET between the two groups; therefore, the higher plasma levodopa peak could not be ascribed to the difference in the GET. In the NC subjects, plasma peak levodopa level was positively correlated with the GET, however, inverse correlation was observed in the PD patients, suggesting the presence of qualitative difference in the levodopa absorption mechanism between early PD and normal population. Enhanced levodopa absorption may be a useful early marker for PD.