Parkinson disease (PD) is a progressive neurodegenerative disease that affects more than 1,000,000 Americans. Currently there is no proven therapy to reduce the rate of progression of PD. In a previous phase II clinical trial, investigators demonstrated that Coenzyme Q10 (CoQ) at dosages of 300, 600, and 1200 mg/day was safe and well-tolerated in individuals with early, untreated PD. The findings also suggested that CoQ may slow the progressive impairment of PD as measured by the Unified Parkinson Disease Rating Scale (UPDRS). In this study, researchers will conduct a randomized, placebo-controlled, phase III trial of CoQ to confirm and extend the results of the earlier phase II study. The primary objective of this trial is to compare the effect of two dosages of CoQ (1200 and 2400 mg/day) and placebo on the total UPDRS score in people with early PD. The study also will evaluate independent function, cognition, and quality of life. Plasma CoQ levels will be measured at months 1, 8 and 16 and correlated with changes in UPDRS scores. Participants will be randomly assigned to receive a placebo (an inactive substance), 1200 mg/d CoQ, or 2400 mg/d CoQ. They will be evaluated at screening, baseline, and during visits at months 1, 4, 8, 12, and 16. Information gained from this trial could lead to changes in management of people with early PD.
Inclusion Criteria: - Presence of all 3 of the cardinal features of Parkinson disease (resting tremor, bradykinesia and rigidity). The clinical signs must be asymmetric. - The diagnosis of Parkinson disease within 5 years prior to the Screening Visit. - Age 30 or older. - Female subjects must not be of childbearing potential or must use an approved form of contraception for the duration of the trial. Exclusion Criteria: - Use of any Parkinson disease medication within 60 days prior to the Baseline Visit. - Duration of previous use of symptomatic medication for Parkinson disease cannot exceed 90 days such as levodopa, dopaminergic agonists (including ropinirole, pramipexole, pergolide, cabergoline, and the rotigotine transdermal system), selegiline, rasagiline, amantadine, and anticholinergic agents. - Parkinsonism due to drugs including neuroleptics, alphamethyldopa, reserpine, metoclopramide, valproic acid. - Use of antioxidants (such as selegiline, rasagiline, vitamins E and C), additional supplemental vitamins or minerals, regular use of neuroleptics, chloramphenicol, valproic acid, warfarin. - Other parkinsonian disorders. - Modified Hoehn and Yahr score of 3 or greater at Screening Visit or Baseline Visit. - UPDRS tremor score of 3 or greater at Screening Visit or Baseline Visit. - Mini-Mental State Examination (MMSE) score of 25 or less. - History of stroke. - Disability sufficient to require treatment with dopaminergic medication or anticipated need for dopaminergic medication within next 3 months. - Other serious illness, including psychiatric illness. - Patients with active cardiovascular, peripheral vascular or cerebrovascular disease within the past year. - Clinically serious abnormalities in the Screening Visit laboratory studies or electrocardiogram. - Use of methylphenidate, cinnarizine, reserpine, amphetamine or a MAO-A inhibitor within 6 months prior to the Baseline Visit. - Unstable dose of CNS active therapies. - Use of appetite suppressants within 60 days prior to the Baseline Visit. - History of active epilepsy within the last 5 years. - Revised Hamilton Rating Scale for Depression of 11 or greater. - Participation in other drug studies or use of other investigational drugs within 30 days prior to Screening Visit. - History of electroconvulsive therapy. - History of any brain surgery for Parkinson disease. - History of structural brain disease such as prior trauma causing damage detected on a CT scan or MRI, hydrocephalus, or prior brain neoplasms.