Coenzyme Q10 : Safety and Interactions

by MedlinePlus

(Page 3 of 3)

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

In theory, allergic reactions to supplements containing CoQ10 may occur.

Side Effects and Warnings

There are few serious reported side effects of CoQ10. Side effects are typically mild and brief, stopping without any treatment needed. Reactions may include nausea, vomiting, stomach upset, heartburn, diarrhea, loss of appetite, skin itching, rash, insomnia, headache, dizziness, irritability, increased light sensitivity of the eyes, fatigue, or flu-like symptoms.

CoQ10 may lower blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a healthcare provider, and medication adjustments may be necessary.

Low blood platelet number was reported in one person taking CoQ10. However, other factors (viral infection, other medications) may have been responsible. Lowering of platelets may increase the risk of bruising or bleeding, although there are no known reports of bleeding from CoQ10. Caution is advised in people who have bleeding disorders or who are taking drugs that increase the risk of bleeding. Dosing adjustments may be necessary.

CoQ10 may decrease blood pressure, and caution is advised in patients with low blood pressure or taking blood pressure medications. Elevations of liver enzymes have been reported rarely, and caution is advised in people with liver disease or taking medications that may harm the liver. CoQ10 may lower blood levels of cholesterol or triglycerides. Thyroid hormone levels may be altered based on one study.

Organ damage due to lack of oxygen/blood flow during intense exercise has been reported in a study of patients with heart disease, although the specific role of CoQ10 is not clear. Vigorous exercise is often discouraged in people using CoQ10 supplements.

Pregnancy and Breastfeeding

There is not enough scientific evidence to support the safe use of CoQ10 during pregnancy or breastfeeding.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

In theory and based on a human case report, coenzyme Q10 may reduce the effectiveness of warfarin (Coumadin®), and may limit or prevent effective anticoagulation (blood "thinning"). CoQ10 may reduce blood pressure and may add to the effects of other blood pressure lowering drugs. In theory, CoQ10 may affect thyroid hormone levels and alter the effects of thyroid drugs such as levothyroxine (Synthroid®), although this has not been proven in humans.

Based on theory and human research, a number of drugs may deplete natural levels of CoQ10 in the body. It has not been shown that there are benefits of CoQ10 supplements in people using these agents. Examples include: diabetes drugs such as chlorpropamide, glimepiride, glipizide, glyburide, metformin, tolazamide, tolbutamide, acetohexamide; methyldopa; clonidine; gemfibrozil; tricyclic antidepressant drugs such as amitriptyline, clomipramine, doxepin, imipramine, trimipramine; antipsychotic medications such as chlorpromazine, fluphenazine, haloperidol, mesoridazine, prochlorperazine, promethazine, thioridazine, trifluoperazine, trimipramine; beta-blocker drugs such as acebutolol, atenolol, betaxolol, bisoprolol, carvedilol, esmolol, labetalol, metoprolol, nadolol, penbutolol, pindolol, propanolol, sotalol, timolol; HMG-CoA reductase inhibitors ("statins") such as atorvastatin, cerivastatin (no longer available in U.S.), fluvastatin, lovastatin, pravastatin, simvastatin; and diuretic drugs ("water pills") such as benzthiazide, hydralazine, chlorthiazide, hydrochlorothiazide, indapamide, methyclothiazide, metolazone, polythiazide.

Interactions with Herbs and Dietary Supplements

CoQ10 may reduce blood pressure and may result in additive effects when taken with other herbs or supplements that also lower blood pressure. Herbs that may lower blood pressure include aconite/monkshood, arnica, baneberry, betel nut, bilberry, black cohosh, bryony, calendula, california poppy, coleus, curcumin, eucalyptol, eucalyptus oil, ginger, goldenseal, green hellebore, hawthorn, Indian tobacco, jaborandi, mistletoe, night blooming cereus, oleander, pasque flower, periwinkle, pleurisy root, shepherd's purse, Texas milkweed, turmeric, and wild cherry. Diuretic herbs such as licorice and horsetail may also decrease blood pressure and therefore interact with CoQ10.

Based on human study, vitamin E may reduce CoQ10 blood levels. In theory, red rice yeast may decrease CoQ10 levels. CoQ10 may add to the effects or side effects of L-carnitine.

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