title: Noninvasive monitoring of plasma L-dopa concentrations using sweat samples in Parkinson's disease.
abstract: 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.
authors.affiliation: Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Tsunoda
authors.affiliation: Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya 461-8673, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hirayama
authors.affiliation: Pico-device Co. Ltd, 2-22-8 Chikusa, Chikusa-ku, Nagoya 464-0858, Japan. Electronic address: tsuda@pico-device.co.jp.
authors.forename: Takao
authors.initials: T
authors.lastname: Tsuda
authors.affiliation: Division of Neurogenetics, Center for Neurological Diseases and Cancer, Nagoya University Graduate School of Medicine, 65 Tsurumai, Showa-ku, Nagoya 466-8550, Japan. Electronic address: ohnok@med.nagoya-u.ac.jp.
authors.forename: Kinji
authors.initials: K
authors.lastname: Ohno
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D006801:Humans; D007980:Levodopa / Q000097:blood* / Q000627:therapeutic use; D010300:Parkinson Disease / Q000097:blood* / Q000188:drug therapy; D013542:Sweat / Q000737:chemistry*
chemical_list: D007980:Levodopa
keywords: Parkinson's disease; Plasma l-dopa; Sweat l-dopa