摘要：Background: l-dopa (l-3,4-dihydroxyphenylalanine) is commonly used for treating Parkinson's disease (PD). However, regardless of its prominent effect, therapeutic range of l-dopa narrows down with disease progression, which leads to development of motor complications including wearing off and dyskinesias. In addition, intestinal absorption of l-dopa is inversely correlated with the amount of oral protein intake, and shows intra- and inter-day variability. Hence, frequent monitoring of plasma l-dopa concentrations is beneficial, but frequent venipuncture imposes physical and psychological burdens on patients with PD.Methods: We investigated the usefulness of sweat samples instead of plasma samples for monitoring l-dopa concentrations. With a monolithic silica disk-packed spin column and the high-performance liquid chromatography-electrochemical detection system, l-dopa in sweat samples was successfully quantified and analyzed in 23 PD patients.Results: We found that the Pearson's correlation coefficient of the plasma and sweat l-dopa concentrations was 0.678. Although the disease durations and severities were not correlated with the deviation of the actual sweat l-dopa concentrations from the fitted line, acquisition of the sweat samples under a stable condition was technically difficult in severely affected patients. The deviations may also be partly accounted for by skin permeability of l-dopa.Conclusions: Measuring l-dopa concentrations in sweat is suitable to get further insights into the l-dopa metabolism.• In Parkinson's disease (PD), stable plasma l-dopa concentrations are required. • Frequent venipuncture imposes physical and psychological burdens on PD patients. • We developed a method to quantify sweat l-dopa concentrations. • Correlation coefficient of plasma and sweat l-dopa concentrations was 0.678. • Sweat is a noninvasive source for estimating plasma l-dopa concentrations.