Reevaluation of levodopa therapy for the treatment of advanced Parkinson's disease.

Levodopa is the most appropriate drug in theory for supplementing dopamine deficiency in the brain of Parkinson's disease (PD) patients. In consideration of the pharmacological properties of levodopa, measurement of 3,4-dihydroxyphenylalanine (DOPA) plasma concentration is significant and important in daily medical care. Akinesia of advanced PD patients comprises a combination of two distinct symptoms, hypokinesia and bradykinesia. It is probable that hypokinesia in PD does not originate from failure of neural pathways from the substantia nigra to motor striatum but is associated with dysfunction of the limbic striatum. Herein the pathophysiologic condition of the limbic striatum in PD patients is discussed and reasons suggested why drug efficacy of dopamine replenishment in this system is meager.