Currently, three COMT inhibitor preparations are available for clinical use, including entacapone and opicapone.217,226 Monoamine oxidase type B (MAO-B) is a primary clearance mechanism for synaptically released DA in glial cells.227 Inhibiting MAO-B (e.g., through selective inhibitor selegiline) prolongs DA’s effect and increases its synaptic concentrations.228 However, because selegiline is irreversible, safinamide has emerged as a reversible MAO-B inhibitor for use in PD treatments.229. Here, COMT is linked to Parkinson disease.