At present,
dopamine agonists play an important role in antiparkinsonian therapy since they were proved effective in the management of both advanced- and early-stage
Parkinson's disease. In the latter, they are often regarded as first-choice medication to delay the introduction of
levodopa therapy. Despite sharing the capacity to directly stimulate
dopamine receptors,
dopamine agonists show different pharmacological properties as they act on different subsets of
dopamine receptors. This, in theory, provides the advantage of obtaining a different antiparkinsonian activity or safety profile with each agent. However, there is very little evidence that any of the marketed
dopamine agonists should be consistently preferred in the management of patients with
Parkinson's disease.
Pergolide and
cabergoline are now considered a second-line choice after the proven association with valvular
fibrosis.
Transdermal administration (
rotigotine) and
subcutaneous infusion (
apomorphine) of
dopamine receptor agonists are now available alternatives to
oral administration and provide continuous dopaminergic stimulation. Continuous subcutaneous
apomorphine infusion during waking hours leads to a large reduction in daily 'off' time,
dyskinesias and
levodopa daily dose. Almost all currently used
dopamine agonists are able to provide neuroprotective effects towards dopaminergic neurons during in vitro and in vivo experiments. This neuroprotection may be the result of different mechanisms including antioxidation, scavenging of
free radicals, suppression of lipid peroxidation and inhibition of apoptosis. However, the disease-modifying effect of these agents in
Parkinson's disease remains to be ascertained.