They directly stimulate dopamine receptors in the brain. They are associated with fewer motor disturbances than occur with long term use of levodopa.

They are as good as levodopa for early PD and are also the second most effective class of drug after the levodopa. They may delay the need of levodopa institution. They may be more useful in younger patients who are more prone to early development of levodopa-related motor disturbances and who will have to be treated for a longer time than those with late onset.

They may be less toxic than levodopa as their metabolism does not produce free radicals.

They may delay the disability, if given in combination with the low dose of levodopa in early PD; however, this concept needs more study.

They are comparatively expensive and poorly tolerated by cognitively impaired patients.