The discovery of striatal dopamine deficiency and the introduction of levodopa in the 1960s as treatment for the motor symptoms of Parkinson disease revolutionized neurology and neurotherapeutics. For the first time, patients with an apparently hopeless chronic degenerative brain disorder were able to regain function and return to the mainstream of life. Levodopa was subsequently combined with carbidopa, as the latter prevented the adverse effects associated with peripheral dopamine synthesis without blocking central dopamine synthesis.
Weiss HD, Pontone GM. Dopamine Receptor Agonist Drugs and Impulse Control Disorders. JAMA Intern Med. 2014;174(12):1935-1937. doi:10.1001/jamainternmed.2014.4097