Caffeine and the antiparkinsonian response to levodopa or piribedil.

The ability of orally administered caffeine to modify the antiparkinsonian efficacy of levodopa of piribedil, a putative dopamine receptor against, was studied in six patients. At doses that induced unequivocal central nervous system stimulation, caffeine produced no change in the therapeutic response to either antiparkinsonian agent. On the other hand, patients with levodopa dyskinesias reported an increase in the duration of their involuntary movements with caffeine coadministration. Since caffeine is known to stimulate both dopaminergic mechanisms and motor activity in the experimental animal, the results of this study cast doubt on the value of these factors as predictors of therapeutic efficacy in parkinsonian patients.