Pramipexole dihydrochloride hydrate is a selective dopamine D2-type receptor agonist, with Kis of 2.2 nM, 3.9 nM, 0.5 nM and 1.3 nM for D2-type receptor, D2, D3 and D4 receptors, respectively. Pramipexole dihydrochloride hydrate can be used for the research of Parkinson's disease (PD) and restless legs syndrome (RLS). Pramipexole dihydrochloride hydrate can cross the blood-brain barrier (BBB).