No serious toxicity associated with the use of coenzyme Q10 has been reported.[1-4] Doses of 100 mg /day or higher have caused mild insomnia in some individuals. Liver enzyme elevation has been detected in patients taking doses of 300 mg/day for extended periods of time, but no liver toxicity has been reported. Researchers in one cardiovascular study reported that coenzyme Q10 caused rashes, nausea, and epigastric (upper abdominal) pain that required withdrawal of a small number of patients from the study. Other reported side effects have included dizziness, photophobia (abnormal visual sensitivity to light), irritability, headache, heartburn, and fatigue.
Certain lipid -lowering drugs, such as the statins (lovastatin, pravastatin, and simvastatin) and gemfibrozil, as well as oral agents that lower blood sugar, such as glyburide and tolazamide, cause a decrease in serum levels of coenzyme Q10 and reduce the effects of coenzyme Q10 supplementation.[1,7-9] Beta-blockers (drugs that slow the heart rate and lower blood pressure) can inhibit coenzyme Q10-dependent enzyme reactions. The contractile force of the heart in patients with high blood pressure can be increased by coenzyme Q10 administration. Coenzyme Q10 can reduce the body’s response to the anticoagulant drug warfarin. Finally, coenzyme Q10 can decrease insulin requirements in individuals with diabetes.References
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- Baggio E, Gandini R, Plancher AC, et al.: Italian multicenter study on the safety and efficacy of coenzyme Q10 as adjunctive therapy in heart failure. CoQ10 Drug Surveillance Investigators. Mol Aspects Med 15 (Suppl): s287-94, 1994. [PUBMED Abstract]
- Feigin A, Kieburtz K, Como P, et al.: Assessment of coenzyme Q10 tolerability in Huntington's disease. Mov Disord 11 (3): 321-3, 1996. [PUBMED Abstract]
- Kaikkonen J, Nyyssönen K, Tuomainen TP, et al.: Determinants of plasma coenzyme Q10 in humans. FEBS Lett 443 (2): 163-6, 1999. [PUBMED Abstract]
- Thibault A, Samid D, Tompkins AC, et al.: Phase I study of lovastatin, an inhibitor of the mevalonate pathway, in patients with cancer. Clin Cancer Res 2 (3): 483-91, 1996. [PUBMED Abstract]
- Coenzyme Q10. In: Jellin JM, Hitchens K, eds.: Natural Medicines Comprehensive Database. Stockton, Calif: Therapeutic Research Faculty, 1999, pp 241-42.