d-DOPA(D-3,4-dihydroxyphenylalanine;dextrodopa) is similar to L-DOPA (levodopa), but with opposite chirality. Levo- and dextro- rotation refer to a molecule's ability to rotate planes of polarized light in one or the other direction. Whereas L-DOPA is moderately effective in the treatment of Parkinson's disease (PD) and dopamine-responsive dystonia (DRD) by stimulating the production of dopamine in the brain, D-DOPA is biologically inactive.