The effects of L-dopa on excessive daytime sleepiness in narcolepsy

We examined the effects of L-dopa on the excessive daytime sleepiness of six narcoleptic patients while using a double-blind design and objective measurements of vigilance. The two treatment periods, L-dopa or placebo, lasted for 2 weeks each, separated by a 1-week washout period. In addition to the standard Multiple Sleep Latency Test (MSLT), two different tests assessed the daytime vigilance: the Analogue Vigilance Scale (AVS) and the Four Choice Reaction Time Test (FCRTT). L-dopa improved vigilance and performance as evaluated by the AVS and the FCRTT, while the capacity to fall asleep rapidly remained unchanged as evaluated by the MSLT. Results of the present study suggest that L-dopa is effective in improving the vigilance level of narcoleptic patients and raises the hypothesis that dopamine may play a role in the physiopathology of excessive daytime sleepiness of this condition.