dopamine agonist

Parkinson's disease destroys the brain cells that make dopamine, the chemical messenger the brain uses to produce smooth, purposeful movement. The main treatment, levodopa, replaces the missing dopamine: nerve cells turn it into the chemical itself. A dopamine agonist takes a different route. It does not become dopamine. It attaches to the receptors on brain cells that dopamine normally uses, the docking sites through which the signal arrives, and switches them on in dopamine's place.

Dopamine receptors come in several types, and which ones a drug acts on shapes its side effects. A 2024 review in CNS and Neurological Disorders Drug Targets notes that the agonists available until recently act strongly on the D2 and D3 types, that many of their adverse effects are linked to that repeated stimulation, and that they are less effective than levodopa against motor symptoms. Tavapadon, approved in the United States in September 2026, acts selectively on the D1 and D5 types instead. The TEMPO-3 trial report in JAMA Neurology describes the older drugs as giving extra motor control alongside levodopa at the cost of a higher risk of adverse events through D2 and D3 activation.