I read with great interest the study of the effects of coenzyme Q10 (CoQ10) in early Parkinson disease by Shults et al and the Parkinson Study Group.1 Commendably, Shults and colleagues examined 3 levels of dosing and recorded changes in the blood (plasma) CoQ10 level. The level of plasma CoQ10increased significantly in the groups receiving CoQ10; however, the increases observed do not appear particularly large considering the doses received. The plasma CoQ10level increased from approximately 0.5 mg/L to about 1.8, 2.2, and 4.0 mg/L, respectively, with 300, 600, and 1200 mg/d of CoQ10. One explanation may be that CoQ10pharmacokinetics is affected by Parkinson disease, although serum CoQ10 levels were not found to differ significantly in 33 patients with Parkinson disease and 31 matched controls.2 Another possibility may be the antagonism of CoQ10 uptake by the high dose (1200 IU) of vitamin E received by the subjects in the study of Shults and colleagues. In a study with patients who had mild hypercholesterolemia,3 200 mg of CoQ10 (100 mg twice daily) increased the plasma CoQ10 level from 0.72 to 4.66 mg/L; however, when 700 mg (350 mg twice a day) of vitamin E (as d-α-tocopherol) was also given, the plasma CoQ10level increased only from 0.84 to 2.71 mg/L. A study with rats found vitamin E to enhance or suppress the accumulation of CoQ10in various tissues in a dose-dependent manner, although no significant differences in brain or serum levels were observed.4 Thus, investigation of possible pharmacokinetic interactions between CoQ10 and vitamin E in humans appears warranted if vitamin E is to be included in future studies of CoQ10in Parkinson disease and other conditions.
Hunter DA. Coenzyme Q10 in Early Parkinson Disease. Arch Neurol. 2003;60(8):1170. doi:10.1001/archneur.60.8.1170-a