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. 
   
   

Glossary Terms

Having to do with the abdomen, which is the part of the body between the chest and the hips that contains the pancreas, stomach, intestines, liver, gallbladder, and other organs.

A drug that helps prevent blood clots from forming. Also called blood thinner.

A tissue with red blood cells, white blood cells, platelets, and other substances suspended in fluid called plasma. Blood takes oxygen and nutrients to the tissues, and carries away wastes.

The force of circulating blood on the walls of the arteries. Blood pressure is taken using two measurements: systolic (measured when the heart beats, when blood pressure is at its highest) and diastolic (measured between heart beats, when blood pressure is at its lowest). Blood pressure is written with the systolic blood pressure first, followed by the diastolic blood pressure (for example 120/80).

Having to do with the heart and blood vessels.

A type of research study that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease. Also called clinical trial.

A nutrient that the body needs in small amounts to function and stay healthy. Coenzyme Q10 helps mitochondria (small structures in the cell) make energy. It is an antioxidant that helps prevent cell damage caused by free radicals (highly reactive chemicals). Coenzyme Q10 is fat-soluble (can dissolve in fats and oils) and is found in fatty fish, beef, soybeans, peanuts, and spinach. It is being studied in the prevention and treatment of some types of cancer and heart disease and in the relief of side effects caused by some cancer treatments. Also called CoQ10, Q10, ubiquinone, and vitamin Q10.

Any of several diseases in which the kidneys make a large amount of urine. Diabetes usually refers to diabetes mellitus in which there is also a high level of glucose (a type of sugar) in the blood because the body does not make enough insulin or use it the way it should.

The amount of medicine taken, or radiation given, at one time.

A protein that speeds up chemical reactions in the body.

Having to do with the upper middle area of the abdomen.

A condition marked by extreme tiredness and inability to function due lack of energy. Fatigue may be acute or chronic.

A blood pressure of 140/90 or higher. High blood pressure usually has no symptoms. It can harm the arteries and cause an increase in the risk of stroke, heart attack, kidney failure, and blindness. Also called hypertension.

Difficulty in going to sleep or getting enough sleep.

A hormone made by the islet cells of the pancreas. Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy.

Fat.

A large organ located in the upper abdomen. The liver cleanses the blood and aids in digestion by secreting bile.

A measure of weight. A milligram is approximately 450,000 times smaller than a pound and 28,000 times smaller than an ounce.

A feeling of sickness or discomfort in the stomach that may come with an urge to vomit. Nausea is a side effect of some types of cancer therapy.

By or having to do with the mouth.

A condition in which the eyes are more sensitive than normal to light.

The active ingredient in a drug used to lower the amount of cholesterol in the blood and to prevent stroke and heart attack. It is also being studied in the treatment of cancer and other conditions. Pravastatin blocks an enzyme that helps make cholesterol in the body. It may also make tumor cells more sensitive to anticancer drugs. It is a type of HMG-CoA reductase inhibitor, a type of statin, and a type of chemosensitizer.

The clear liquid part of the blood that remains after blood cells and clotting proteins have been removed.

A problem that occurs when treatment affects healthy tissues or organs. Some common side effects of cancer treatment are fatigue, pain, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores.

Any of a group of drugs that lower the amount of cholesterol and certain fats in the blood. Statins inhibit a key enzyme that helps make cholesterol. Statin drugs are being studied in the prevention and treatment of cancer.

Adding nutrients to the diet.

Having to do with poison or something harmful to the body. Toxic substances usually cause unwanted side effects.

A drug that prevents blood from clotting. It belongs to the family of drugs called anticoagulants (blood thinners).