Continuous dopaminergic stimulation in Parkinson's disease.

Complex motor fluctuations and dyskinesias ("on-off" phenomenon) in Parkinson's disease can be corrected by parenteral administration of levodopa, levodopa-methyl-ester, lisuride and apomorphine. Levodopa and levodopa-methyl-ester may only be administered intravenously because of their low solubility. Lisuride and apomorphine are readily absorbed after subcutaneous administration. Repeated or continuous intravenous infusions of levodopa have been given for a few days, using a wearable "jacket-like" pump, with good results. So far, lisuride is the only dopamine agonist used for chronic treatment by continuous infusion. The "on-off" effect is adequately controlled in most patients by subcutaneous lisuride administration (plus oral levodopa). However, adverse effects, particularly psychiatric complications, constitute a major limiting factor for routine applications of this form of treatment. Subcutaneous apomorphine infusion is unlikely to become a standard therapeutic procedure in Parkinson's disease, but it is a very valuable research method to gain further insight into the pathophysiology of motor fluctuations in Parkinson's disease.