Medical Author : Dennis Lee, M.D.
Medical Editor: Daniel Kulick, M.D.

• What are fibrates?
• What are the side effects of fibrates?

What are fibrates?

Fibric acid derivatives (fibrates) are a class of medications that lower blood triglyceride levels. Fibrates lower blood triglyceride levels by reducing the liver 's production of VLDL (the triglyceride-carrying particle that circulates in the blood) and by speeding up the removal of triglycerides from the blood. Fibrates are also modestly effective in increasing blood HDL cholesterol levels; however, fibrates are not effective in lowering LDL cholesterol. Examples of fibrates available in the United Sates include gemfibrozil (Lopid) and fenofibrate (Tricor).

Very high triglyceride levels (usually >1000 mg/dl) can cause pancreatitis (inflammation of the pancreas that can result in a serious illness with severe abdominal pain ). By lowering blood triglycerides, fibrates are used to prevent pancreatitis.

Fibrates are not effective in lowering LDL cholesterol ; however, when a high risk patient (see NCEP recommendations) also has high blood triglyceride or low HDL cholesterol levels, doctors may consider combining a fibrate, such as fenofibrate (Tricor), with a statin. Such a combination will not only lower LDL cholesterol but will also lower blood triglycerides and increase HDL cholesterol levels.

Fibrates have also been used alone to prevent heart attacks especially in patients with elevated blood triglycerides and low HDL cholesterol levels. In one large study, gemfibrozil decreased the risk of heart attacks but did not affect the overall survival of persons with high cholesterol levels.

What are the side effects of fibrates?

The side effects of fibrates include nausea, stomach upset, and sometimes diarrhea. Fibrates can irritate (inflame) the liver. The liver irritation usually is mild and reversible, but it occasionally can be severe enough to require stopping the drug.

Fibrates can cause gallstones when used over several years.

Fibrates can increase the effectiveness of blood thinners, such as warfarin (Coumadin), when both medications are used together. Thus, the dose of warfarin should be adjusted to avoid over-thinning of the blood which can lead to excessive bleeding.

Fibrates can cause muscle damage particularly when taken together with statin medications.  Gemfibrozil interferes with the breakdown of statins, resulting in higher statin blood levels, and hence a higher likelihood of muscle toxicity from the statin. Doctors generally avoid combining a statin with gemfibrozil because of concern over the higher risk of muscle damage with the combination; however, fenofibrate does not interfere with the breakdown of statins and should be the safer fibrate to use whenever it is necessary to use a fibrate with a statin. Furthermore, pravastatin seems to have fewer muscle toxic effects than the other statins when combined with fibrates.

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