The Place of the Dopaminergic Agonists in the Treatment of Parkinson's Disease: The View from the Trenches

Abstract

The use of the dopamine receptor agonists in Parkinson's disease has a compelling logic. These agents are supposed to act independently of the dying cells of the substantia nigra directly on the cells of the striatum. Early clinical trials in advanced disease were only mildly impressive. Later they were found to be beneficial in early disease but their effectiveness waned. Their ultimate failure may reflect the fact that the majority of current agents do not stimulate D1 and D2 receptors in a physiologic ratio. The drugs may act presynaptically and with the eventual loss of the anatomic relationships between nigra and striatum the drugs fail. There is, however, a rationale to their current use. When used along with L-Dopa in early disease the development of late-stage fluctuations are reduced with the same anti-parkinsonian benefits. Merging this concept with the demonstrated effect of selegiline in slowing the course of the disease, the current practice of triple therapy with selegiline, L-Dopa and a dopamine receptor agonist emerges. © 1992, Canadian Neurological Sciences Federation. All rights reserved.