COMT and Parkinson disease: Currently there are no therapeutic interventions that can prevent, delay, stop or reverse the progression of PD, but only symptomatic treatments, with net benefits that diminish as the disease advances (i.e., for parkinsonism mainly levodopa with a decarboxylase inhibitor, dopamine receptor agonists, catechol-O methyltransferase inhibitors, and monoamine oxidase inhibitors) [1,6].