- If subject is taking Levodopa (L-DOPA) and derivatives, Monoamine Oxidase (MAO) B-inhibitors, anticholinergics agents, Catechol-O-Methyl Transferase (COMT) inhibitor or N-Methyl-D-Aspartate (NMDA) antagonist, he/she must have been on stable dose for at least 28 days prior to the Screening Visit