L-DOPA induced-endogenous 6-hydroxydopamine is the cause of aggravated dopaminergic neurodegeneration in Parkinson's disease patients.

Dopamine replacement therapy by 3,4-dihydroxyphenylalanine (L-DOPA), which is the gold standard symptomatic treatment for the Parkinson's disease (PD), frequently leads to potential debilitating side-effects such as dyskinesia. One of the most significant molecules reported to be produced endogenously in the brain is 6-hydroxydopamine (6-OHDA), contributed solely by unsequestered dopamine in neurons derived from L-DOPA. It is further demonstrated that scavengers of hydroxyl radicals such as melatonin and salicylic acid inhibited its generation. However no reports on the level of 6-OHDA and hydroxyl radicals generated in vivo in human brain is known. Oxidative stress and mitochondrial dysfunction are known to be associated with Lewy body formation, which is directly dependent on the levels of free dopamine. Therefore, it is hypothesized that L-DOPA induced increase in endogenous 6-OHDA levels will have the ability to cause oxidative stress and mitochondrial dysfunctions that eventually leads to Lewy body formation in dopaminergic neurons resulting in its degeneration. Concomitant use of potent anti-oxidants along with L-DOPA would help in attenuating the neurodegeneration caused by endogenous 6-OHDA and would ultimately delay the progression of PD.