Dopamine agonists used as monotherapy in de novo PD patients: comparisons with selegiline.

Studies indicate that selegiline, a monoamine oxidase type B inhibitor, slows progression of Parkinson's disease (PD) and delays the need for levodopa. While dopamine agonists also delay the need for levodopa because of their symptomatic, antiparkinsonian effect, only recently has it been proposed that agonists may also have a protective effect. When dopamine agonists are used as monotherapy in newly diagnosed PD patients, fewer patients improve than on levodopa, but fewer patients develop response fluctuations. This might indicate that dopamine agonists have a protective, as well as a symptomatic, effect, as the lack of response fluctuations may indicate that dopamine agonists protect nigral neurons. Response fluctuations may result from destruction of nigral neurons.