Inhibiting COMT in Parkinson's Disease

Inclusion Criteria: * Age 60 - 75 years, * Caucasian ethnicity, * diagnosed PD by UK brain bank criteria, * Hoehn \& Yahr scale 2 - 3, * fertile females have to use contraception * Group 1: medication with Stalevo® (L-DOPA/DDI + Entacapone) * Group 2: medication with Madopar® or Sinemet® (L-DOPA/DDI) Exclusion Criteria: * methotrexate therapy during the last 12 months, * treatment with Tolcapone * vitamin B6, B12 and/or folic acid supplementation during last 6 months, * pregnancy, * intention to become pregnant during the course of the study, * breast feeding, * other clinically relevant concomitant disease states by discretion of the investigator * known or suspected non-compliance, drug or alcohol abuse, * inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia or confusional state of the subject, * participation in another study with investigational drug within the 30 days preceding and during the present study, * enrolment of the investigator, his/her family members, employees and other dependent persons.