Levodopa-induced drowsiness in healthy volunteers: results of a choice reaction time test combined with a subjective evaluation of sedation

Clin Neuropharmacol. 2001 Mar-Apr;24(2):91-4. doi: 10.1097/00002826-200103000-00004.


The aim of the present study was to assess levodopa (L-Dopa)-induced drowsiness in healthy volunteers using two parameters: choice reaction time and a subjective rating of sedation. Sixteen subjects participated in a randomized, double-blinded, crossover study. A single dose of 200 mg L-Dopa or placebo was administered at 9:00 AM. To limit peripheral side effects connected with L-Dopa, subjects were treated with 20 mg domperidone three times daily. Subjective rating of sedation consisted of visual analogue scale. Reaction time was measured by means of responses to two light-emitting diodes. The illumination of one of these diodes constituted the imperative signal. Manual responses were performed on two buttons located under the right and left index fingers. Results demonstrated a positive correlation between sedation level and reaction time (r = 0.70, p = 0.0026). Adverse events of L-Dopa were nausea (four cases) and excitation (one case). Subjects who did not develop adverse events were faster under L-Dopa than under placebo (p = 0.02), whereas subjects who had nausea or excitation were slower. A single dose of L-Dopa either deteriorated or improved choice reaction time in healthy volunteers according to whether it was sedative and whether it generated disruptive adverse events.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antiparkinson Agents / pharmacology*
  • Chi-Square Distribution
  • Choice Behavior / drug effects*
  • Choice Behavior / physiology
  • Cross-Over Studies
  • Double-Blind Method
  • Female
  • Humans
  • Hypnotics and Sedatives / pharmacology*
  • Levodopa / pharmacology*
  • Male
  • Reaction Time / drug effects*
  • Reaction Time / physiology
  • Sleep Stages / drug effects*
  • Sleep Stages / physiology


  • Antiparkinson Agents
  • Hypnotics and Sedatives
  • Levodopa