Homocysteine and levodopa: should Parkinson disease patients receive preventative therapy?

Epidemiologic evidence has linked elevation of serum homocysteine to an increased risk of coronary artery disease, stroke, and dementia. An increase in homocysteine levels in Parkinson disease (PD) recently has been discovered. Although B vitamin status and genetic factors are important modifying influences determining the degree of this elevation, the main cause appears to be therapy with L-dopa. It has been suggested that breakdown of L-dopa by catechol-O-methyltransferase results in increased homocysteine formation. Therefore, there are reasons to suggest that management of PD may render patients at increased risk of stroke, heart disease, dementia, and even accelerated nigral degeneration. At present, no controlled prospective studies have evaluated this phenomenon, although they are ongoing.