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

The aim of the present study was to assess levodopa (L-Dopa)-induced drowsi ness in healthy volunteers using two parameters: choice reaction time and a subjective rating of sedation. Sixteen subjects participated in a randomiz ed, double-blinded, crossover study. A single dose of 200 mg L-Dopa or plac ebo was administered at 9:00 AM. To limit peripheral side effects connected with L-Dopa, subjects were treated with 20 mg domperidone three times dail y. Subjective rating of sedation consisted of visual analogue scale. Reacti on time was measured by means of responses to two light-emitting diodes. Th e illumination of one of these diodes constituted the imperative signal. Ma nual responses were performed on two buttons located under the right and le ft index fingers. Results demonstrated a positive correlation between sedat ion level and reaction time (r = 0.70, p = 0.0026). Adverse events of L-Dop a were nausea (four cases) and excitation (one case). Subjects who did not develop adverse events were faster under L-Dopa than under placebo (p = 0.0 2), whereas subjects who had nausea or excitation were slower. A single dos e of L-Dopa either deteriorated or improved choice reaction time in healthy volunteers according to whether it was sedative and whether it generated d isruptive adverse events.