Factors Associated With Motor Fluctuations and Dyskinesia in Parkinson Disease

Abstract

Parkinson disease is a progressive movement disorder caused by loss of dopaminergic neurons in the substantia nigra. Of unknown etiology, Parkinson disease is characterized by 4 cardinal symptoms: tremor at rest, bradykinesia, postural instability, and rigidity. The current criterion-standard drug used in the management of parkinsonian symptoms is levodopa (l-dopa). However, long-term l-dopa therapy is associated with the development of motor complications; approximately 50% to 80% of patients will develop motor complications within 5 to 10 years of l-dopa treatment initiation. Motor complications can be divided into motor fluctuations, caused largely through pulsatile dopamine stimulation and low l-dopa concentrations, and dyskinesia, associated more often with peak l-dopa concentrations. Ultimately, the main goal was to provide steady l-dopa concentrations, without peaks and troughs. Empirical investigations using parenteral infusions of l-dopa and highly soluble l-dopa prodrugs have shown that there is benefit in ameliorating the peaks and troughs associated with traditional oral l-dopa formulations. Recently, the development of highly soluble oral l-dopa prodrugs has facilitated rapid, regular, and reliable l-dopa availability. This review evaluates some of the pharmacologic strategies in the management of motor complications in Parkinson disease and therapy optimization, with a focus on the use of CHF 1512 (Sirio), a combination of melevodopa (l-dopa methylester, a highly soluble prodrug of l-dopa) plus carbidopa in an effervescent tablet formulation.