No serious toxicity associated with the use of coenzyme Q₁₀ has been reported. Reviewed in [1-4] Doses of 100 mg /day or higher have caused mild insomnia in some individuals. Reviewed in [1] 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. Reviewed in [1] 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.[5] Other reported side effects have included dizziness, photophobia (abnormal visual sensitivity to light), irritability,[5] headache, heartburn, and fatigue.[6]

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.[7,8] Reviewed in [1,9] Beta-blockers (drugs that slow the heart rate and lower blood pressure) can inhibit coenzyme Q₁₀-dependent enzyme reactions. Reviewed in [1] The contractile force of the heart in patients with high blood pressure can be increased by coenzyme Q₁₀ administration. Reviewed in [1] Coenzyme Q₁₀ can reduce the body’s response to the anticoagulant drug warfarin. Reviewed in [9] Finally, coenzyme Q₁₀ can decrease insulin requirements in individuals with diabetes. Reviewed in [9]

References

1. Pepping J: Coenzyme Q10. Am J Health Syst Pharm 56 (6): 519-21, 1999.  [PUBMED Abstract]
   
   
2. Overvad K, Diamant B, Holm L, et al.: Coenzyme Q10 in health and disease. Eur J Clin Nutr 53 (10): 764-70, 1999.  [PUBMED Abstract]
   
   
3. Hodges S, Hertz N, Lockwood K, et al.: CoQ10: could it have a role in cancer management? Biofactors 9 (2-4): 365-70, 1999.  [PUBMED Abstract]
   
   
4. Heller JH: Disease, the host defense, and Q-10. Perspect Biol Med 16 (2): 181-7, 1973 Winter.  [PUBMED Abstract]
   
   
5. 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]
   
   
6. 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]
   
   
7. Kaikkonen J, Nyyssönen K, Tuomainen TP, et al.: Determinants of plasma coenzyme Q10 in humans. FEBS Lett 443 (2): 163-6, 1999.  [PUBMED Abstract]
   
   
8. 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]
   
   
9. Coenzyme Q10. In: Jellin JM, Hitchens K, eds.: Natural Medicines Comprehensive Database. Stockton, Calif: Therapeutic Research Faculty, 1999, pp 241-42. 
   
   

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