Drug Interactions:
Statin Drugs

The statin drugs, also known as HMG-CoA reductase inhibitors, are the most popular and powerful medications for lowering cholesterol. They work by interfering with HMG-CoA reductase, an enzyme necessary for the body's manufacture of cholesterol. Drugs in this family include

• atorvastatin calcium (Lipitor)
• fluvastatin (Lescol)
• lovastatin (Mevacor)
• pravastatin (Pravachol)
• simvastatin (Zocor)
• and others

Chaparral, Comfrey, and Coltsfoot

Possible Harmful Interaction

The herb chaparral (Larrea tridentate or L. mexicana) has been promoted for use in arthritis, cancer, and various other conditions, but there is insufficient evidence supporting its effectiveness. There are, however, concerns about its apparent liver toxicity.

Several cases of chaparral-induced liver damage have been reported, some of them severe enough to require liver transplantation.^1–6

Based on these reports, combining chaparral with other agents that are hard on the liver, such as statin drugs, may amplify the risk of potential liver problems.⁷ Other herbs that are toxic to the liver include comfrey (Symphytum officinale) and coltsfoot (Tussilago farfara).

St. John's Wort

Possible Harmful Interaction

The herb St. John’s wort, used to treat depression, may decrease blood levels of various drugs in the statin family, including simvastatin, lovastatin, and atorvastatin (but not pravastatin).²²

Grapefruit Juice

Possible Harmful Interaction

Grapefruit juice impairs the body's normal breakdown of several drugs, including statins, allowing them to build up to potentially excessive levels in the blood.⁸ A recent study indicates that this effect can last for 3 days or more following the last glass of juice.⁹

Because this could increase the risk of serious drug side effects, if you take interacting statins, the safest approach is to avoid grapefruit juice altogether. Grapefruit juice may not affect fluvastatin or pravastatin because these drugs are broken down differently than other statins.¹⁰

Vitamin B3

Possible Benefits and Risks

Niacin (nicotinic acid) is vitamin B₃. In high doses (often 1500 mg daily or more), niacin is effective in lowering cholesterol levels. Its other form, niacinamide (nicotinamide), does not affect cholesterol.

Combining high-dose niacin with statin drugs further improves cholesterol profile by raising HDL (“good”) cholesterol.^23,234,25 Unfortunately, there are real concerns that this combination therapy could cause a potentially fatal condition called rhabdomyolysis.

A growing body of evidence, however, suggests that the risk is relatively slight in individuals with healthy kidneys. Furthermore, even much lower doses of niacin than the usual dose given to improve cholesterol levels (100 mg versus 1000 mg or more) may provide a similar benefit.²⁶ At this dose, the risk of rhabdomyolysis should be decreased. Nonetheless, it is not safe to try this combination except under close physician supervision. Rhabdomyolysis can be fatal.

Red Yeast Rice

Possible Harmful Interaction

Red yeast rice is an herbal cholesterol-lowering therapy. It contains a mixture of statins; its primary statin ingredient is lovastatin, making it most closely resemble the prescription drug Mevacor.

Based on the similarity of red yeast rice to statin drugs, the two should not be combined without medical supervision.

Coenzyme Q10 (CoQ10)

Supplementation Probably Helpful

Coenzyme Q₁₀ (CoQ₁₀) is a vitamin-like substance that plays a fundamental role in the body's energy production^13,14 and appears to be important for normal heart function.¹⁵

Statin drugs inhibit the enzyme necessary for the body's synthesis of both cholesterol and CoQ₁₀. Several studies (including two double-blind trials) have found that these drugs reduce CoQ₁₀ levels in the body.^16,17,18 Because statin drugs are used to protect the heart by lowering cholesterol levels, their effect of inhibiting CoQ₁₀ production might be counterproductive.

Furthermore, statin-induced lowering of tissue CoQ₁₀ levels may worsen heart function in people with cardiomyopathy, a disease of the heart muscle.¹⁹ Individuals most vulnerable to this effect appear to be those with low CoQ₁₀ levels and impaired heart function to begin with. When the study participants were given oral CoQ₁₀ supplementation (100 to 200 mg/day), their CoQ₁₀ blood levels increased and their deteriorating heart function improved.

Fortunately, taking CoQ₁₀ supplements prevents the lowering of CoQ₁₀ levels caused by statin drugs, and does so without interfering with their therapeutic effects.²⁰

Based on this evidence, CoQ₁₀ supplementation may be advisable when taking statin drugs, especially for individuals with poor heart function.

Fish Oil

Supplementation Probably Helpful

Fish oil is thought to help prevent heart disease. A 1-year double-blind placebo-controlled trial found that use of fish oil enhanced the benefits of simvastatin, further reducing triglyceride levels.²¹

Last reviewed March 2002 by Medical Review Board

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