Evidence on the efficacy of high-dose
coenzyme Q10 (
CoQ10) in
Parkinson's disease (PD) is conflicting. An open-label dose-escalation study was performed to examine the effects of
CoQ10 on
biomarkers of oxidative damage and clinical outcomes in 16 subjects with early idiopathic PD. Each dose (400, 800, 1200, and 2400 mg/day) was consumed daily for 2 weeks. High-dose
CoQ10 was well tolerated and improvements in the total Unified Parkinson's Disease Rating Scale (median, 37 vs. 27; p=0.048) were observed following study completion. Plasma
F2-isoprostanes (adjusted for arachidonate) were significantly reduced in the 400-1200 mg/day dose range, but increased at 2400 mg/day dosage. A similar pattern of change was observed with serum
phospholipase A2 activities. Levels of plasma
all trans-retinol, plasma total
tocopherol, serum
uric acid, and serum total
cholesterol were unchanged despite an increase in the
CoQ10 dosage. Subjects with symptomatic benefits from
CoQ10 (decrease in total UPDRS >10 points) had lower baseline plasma
ubiquinol (p=0.07, Mann-Whitney U test) and decreased
F2-isoprostanes per unit arachidonate (p=0.04, Wilcoxon Signed-Ranks test). These results lead to the hypothesis that the therapeutic response to
CoQ10 depends on baseline levels of
ubiquinol and whether the dosage of
CoQ10 used can ameliorate the burden of oxidative damage.