A Cochrane review included 3 studies with a total of 68 subjects. Only 2 of the 3 included studies were pooled in the meta-analysis (n=50), as one study was judged to have an unacceptably high risk of bias. Both studies allowed participants to continue previous anti-hypertensive therapies. Patients took 100 mg–200 mg coenzyme Q10 (also called ubiquinone) daily or a placebo daily for up to 8–12 weeks. Coenzyme Q10 did not significantly change systolic BP (-3.68 mmHg, 95% CI -8.86 to 1.49 mmHg), or diastolic BP (-2.03 mmHg, 95% CI -4.86 to 0.81 mmHg). If the third study had been included in the meta-analysis, a small but statistically significant blood pressure lowering effect of CoQ10 would have been found.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment and blinding), by inconsistency (variability in results), and by imprecise results (few patients).