Idiopathic Parkinson's disease (IPD) results from a largely selective degeneration of nigrostriatal dopaminergic neurons. Therefore, compounds which strengthen dopaminergic transmission in the striatum are the most important therapeutic approach. These include L-dopa, dopamine receptor agonists, selegeline, and entacapon. Since nigrostriatal degeneration leads to secondary alterations of cholinergic and glutamatergic transmission to the basal ganglia,nondopaminergic compounds such as anticholinergics and N-methyl-D-aspartate (NMDA) receptor antagonists are also used in the management of IPD. L-dopa is the most effective substance but after 3-5 years of L-dopa treatment, approximately half of all IPD patients develop fluctuations. Therefore, initial treatment with a dopamine receptor agonist is recommended.