Coenzyme Q10 (ubiquinone) is a compound that is made naturally in the body. A coenzyme is a substance needed for the proper functioning of an enzyme. Cells to produce energy needed for cell growth and maintenance use coenzyme Q10. The body as an antioxidant also uses it. Coenzyme Q10 is found in most body tissues. The highest amounts are found in the heart, liver, kidneys and pancreas.
It has been suggested that coenzyme Q10 has the ability to protect the heart during periods of ischemia (lack of oxygen). A number of small early studies indicated that coenzyme Q10 could help patients with congestive heart failure, and a large clinical trial reported that coenzyme Q10 improved shortness of breath, palpitations, heart rate and blood pressure in patients with stabilized heart failure (Clinical Investigator 1993; 71:S129); however, placebo-controlled double blind studies have not confirmed these positive results (Eur Heart J 1992; 13:1528; J Card Fail 1995; 1:101; Ann Intern Med 2000; 132:636). Studies are currently being conducted using coenzyme Q10 as a dietary supplement in patients undergoing conventional cancer treatment.
Some patients using coenzyme Q10 have experienced mild insomnia, elevated levels of liver enzymes, rashes, nausea, and upper abdominal pain. Other reported side effects have included dizziness, visual sensitivity to light, irritability, headache, heartburn, and fatigue. Coenzyme Q10 may also alter the body's response to warfarin and insulin.