Coenzyme Q ₁₀ is a compound that is made naturally in the body. The Q and the 10 in coenzyme Q₁₀ refer to the groups of chemicals that make up the coenzyme. Coenzyme Q₁₀ is also known by these other names:

A coenzyme helps an enzyme do its job. An enzyme is a protein that speeds up the rate at which natural chemical reactions take place in cells of the body. The body's cells use coenzyme Q₁₀ to make energy needed for the cells to grow and stay healthy. The body also uses coenzyme Q₁₀ as an antioxidant. An antioxidant is a substance that protects cells from chemicals called free radicals. Free radicals can damage DNA (deoxyribonucleic acid). Genes, which are pieces of DNA, tell the cells how to work in the body and when to grow and divide. Damage to DNA has been linked to some kinds of cancer. By protecting cells against free radicals, antioxidants help protect the body against cancer.

Coenzyme Q₁₀ is found in most body tissues. The highest amounts are found in the heart, liver, kidneys, and pancreas. The lowest amounts are found in the lungs. The amount of coenzyme Q₁₀ in tissues decreases as people get older.

Coenzyme Q₁₀ was first identified in 1957. Its chemical structure was determined in 1958. Interest in coenzyme Q₁₀ as a possible treatment for cancer began in 1961, when it was found that some cancer patients had a lower than normal amount of it in their blood. Low blood levels of coenzyme Q₁₀ have been found in patients with myeloma, lymphoma, and cancers of the breast, lung, prostate, pancreas, colon, kidney, and head and neck.

Studies suggest that coenzyme Q₁₀ may help the immune system work better. Partly because of this, coenzyme Q₁₀ is used as adjuvant therapy for cancer. Adjuvant therapy is treatment given following the primary treatment to increase the chances of a cure.

Coenzyme Q₁₀ may be useful in treating cancer because it boosts the immune system. Also, studies suggest that CoQ₁₀ analogs (drugs that are similar to CoQ₁₀) may prevent the growth of cancer cells directly. As an antioxidant, coenzyme Q₁₀ may help prevent cancer from developing.

Refer to the PDQ health professional summary on Coenzyme Q10 for more information on the theory behind the study of coenzyme Q₁₀ in the treatment of cancer.

Coenzyme Q₁₀ is usually taken by mouth as a pill (tablet or capsule). It may also be given by injection into a vein (IV). In animal studies, coenzyme Q₁₀ is given by injection.

A number of preclinical studies have been done with coenzyme Q₁₀. Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. These preclinical studies are done before any testing in humans is begun. Most laboratory studies of coenzyme Q₁₀ have looked at its chemical structure and how it works in the body. The following has been reported from preclinical studies of coenzyme Q₁₀ and cancer:

• Animal studies found that coenzyme Q₁₀ boosts the immune system and helps the body fight certain infections and types of cancer.
• Coenzyme Q₁₀ helped to protect the hearts of study animals that were given the anticancer drug doxorubicin, an anthracycline that can cause damage to the heart muscle.
• Laboratory and animal studies have shown that analogs of coenzyme Q₁₀ may stop cancer cells from growing.

There have been no well-designed clinical trials involving large numbers of patients to study the use of coenzyme Q₁₀ in cancer treatment. There have been some clinical trials with small numbers of people, but the way the studies were done and the amount of information reported made it unclear if benefits were caused by the coenzyme Q₁₀ or by something else. Most of the trials were not randomized or controlled. Randomized controlled trials give the highest level of evidence:

• In randomized trials, volunteers are assigned randomly (by chance) to one of 2 or more groups that compare different factors related to the treatment.
• In controlled trials, one group (called the control group) does not receive the new treatment being studied. The control group is then compared to the groups that receive the new treatment, to see if the new treatment makes a difference.

Some research studies are published in scientific journals. Most scientific journals have experts who review research reports before they are published, to make sure that the evidence and conclusions are sound. This is called peer review. Studies published in peer-reviewed scientific journals are considered better evidence. No randomized clinical trials of coenzyme Q₁₀ as a treatment for cancer have been published in a peer-reviewed scientific journal. 
The following has been reported from studies of coenzyme Q₁₀ in people:A randomized trial of 20 patients looked at whether coenzyme Q₁₀ would protect the heart from the damage caused by the anthracycline drug doxorubicin. The results of this trial and others have shown that coenzyme Q₁₀ decreases the harmful effects of doxorubicin on the heart.

Randomized trial of coenzyme Q₁₀ and doxorubicin

Studies of coenzyme Q₁₀ as an adjuvant therapy for breast cancer

Small studies have been done on the use of coenzyme Q₁₀ after standard treatment in patients with breast cancer:

• In a study of coenzyme Q₁₀ in 32 breast cancer patients, it was reported that some signs and symptoms of cancer went away in 6 patients. Details were given for only 3 of the 6 patients. The researchers also reported that all the patients in the study used less pain medicine, had improved quality of life, and did not lose weight during treatment.


• In a follow-up study, two patients who had breast cancer remaining after surgery were treated with high doses of coenzyme Q₁₀ for 3 to 4 months. It was reported that after treatment with high-dose coenzyme Q₁₀, the cancer was completely gone in both patients.


• In a third study led by the same researchers, 3 breast cancer patients were given high-dose coenzyme Q₁₀ and followed for 3 to 5 years. The study reported that one patient had complete remission of cancer that had spread to the liver, another had remission of cancer that had spread to the chest wall, and the third had no breast cancer found after surgery.

It is not clear, however, if the benefits reported in these studies were caused by coenzyme Q₁₀ therapy or something else. The studies had the following weaknesses:

• The studies were not randomized or controlled.
• The patients used other supplements in addition to coenzyme Q₁₀.
• The patients received standard treatments before or during the coenzyme Q₁₀ therapy.
• Details were not reported for all patients in the studies.

Anecdotal reports of coenzyme Q₁₀

Anecdotal reports are incomplete descriptions of the medical and treatment history of one or more patients. There have been anecdotal reports that coenzyme Q₁₀ has helped some cancer patients live longer, including patients with cancers of the pancreas, lung, colon, rectum, and prostate. The patients described in these reports, however, also received treatments other than coenzyme Q₁₀, including chemotherapy, radiation therapy, and surgery.

No serious side effects have been reported from the use of coenzyme Q₁₀. The most common side effects include the following:

• Insomnia (being unable to fall sleep or stay asleep).
• Higher than normal levels of liver enzymes.
• Rashes.
• Nausea.
• Pain in the upper part of the abdomen.
• Dizziness.
• Feeling sensitive to light.
• Feeling irritable.
• Headache.
• Heartburn.
• Feeling very tired.

It is important to check with health care providers to find out if coenzyme Q₁₀ can be safely used along with other drugs. Certain drugs, such as those that are used to lower cholesterol, blood pressure, or blood sugar levels, may decrease the effects of coenzyme Q₁₀. Coenzyme Q₁₀ may change way the body uses warfarin (a drug that prevents the blood from clotting) and insulin.

As noted in Question 1, the body uses coenzyme Q₁₀ as an antioxidant. Antioxidants protect cells from free radicals. Some conventional cancer therapies, such as anticancer drugs and radiation treatment, kill cancer cells in part by causing free radicals to form. Researchers are studying whether using coenzyme Q₁₀ along with conventional therapies has any effect, good or bad, on the way these conventional therapies work in the body.

Coenzyme Q₁₀ is sold as a dietary supplement and is not approved by the FDA for use as a cancer treatment. In the United States, dietary supplements are regulated as foods, not drugs. This means that approval by the FDA is not required before coenzyme Q₁₀ is sold, unless specific health claims are made about the supplement. Also, the way companies make coenzyme Q₁₀ is not regulated. Different batches and brands of coenzyme Q₁₀ supplements may be different from each other.