3-O-MethyltolcaponeD7 (Ro 40-7591 D7) is a deuterium labeled 3-O-Methyltolcapone. 3-O-Methyltolcapone (Ro 40-7591) is a metabolite of Tolcapone which is a potent COMT inhibitor. Tolcapone crosses the blood-brain barrier and can be used for treatment of P