Is Levodopa Toxic?
Figure 32-2 Oxidative stress hypothesis. Figure 32-2. Oxidative stress hypothesis. Despite its shortcomings, levodopa remains the most effective symptomatic therapy for PD. However, the pervasive and often disabling motor and mental complications associated with chronic levodopa usage have sustained an unresolved debate over the possibility that the drug itself is toxic and contributes to the neurodegeneration (75, 76). It has been postulated that levodopa’s toxicity is based on the formation of oxygen free radicals and other reactive oxygen species (Figure 32-2) (77), which can be destructive to the lipid substructure of cell membranes, among other areas and may lead to cell death. Oxidative reactions are ubiquitous in the human body and are an intrinsic part of the oxidative phosphorylation chain reactions that result in the production of ATP. Hydrogen peroxide and free radical byproducts can react with and damage not only cell membranes but also DNA and proteins (78). Normally, thei
