Dopaminergic agonist effects on Parkinsonian clinical features and brain monamine metabolism.

The effect of a new dopaminergic agonist, piribedil, was studied in 16 patients with Parkinson's disease and compared with placebo and L-DOPA. Piribedil appeared to have a moderate therapeutic effect that was significantly less than that of L-DOPA. Tremor appeared to be the main clinical feature to benefit. Nausea, vomiting, and somnolence were most frequent during the buildup of treatment and confusion and hallucinations during long-term treatment. Piribedil caused a significant decrease in probenecid-induced accumulation of HVA in the CSF, suggesting reduced turnover of endogenous dopamine in the brain. There was a significant relationship between dopamine receptor activation by piribedil and improvement of parkinsonian disability.