Fibrates (or fibric acid derivatives) are a type of cholesterol-reducing drug. These medications lower the levels of fats (lipids) in the blood, including cholesterol and triglycerides. Fibric acid mainly acts to lower triglycerides by reducing their production and increasing the rate at which existing triglycerides are removed from the bloodstream. Fibrates have been shown to reduce triglycerides by 35 to 50 percent in patients who have elevated triglyceride levels (hypertriglyceridemia), according to the National Institutes of Health (NIH).
Other types of cholesterol reducing drugs include statins, bile acid resins and nicotinic acid. All are commonly used to treat high cholesterol (hypercholesterolemia).
In addition to lowering triglycerides, fibrates can also modestly increase HDLs (“good”) cholesterol levels by 15 to 25 percent, according to the NIH. They are less effective at reducing LDL (“bad”) cholesterol levels. There are three types of fibrates currently available in the United States:
- Gemfibrozil (Lopid). Reduces triglycerides and has been shown to increase HDL levels by and average of 11 percent. It is the most commonly prescribed fibrate in the United States. It is usually taken twice a day, preferably 30 minutes before meals.
- Fenofibrate (Lifibra, Tricor, Antara, Lipofen, Triglide). Has been found in clinical studies to slow the progression of coronary artery disease in people with type 2 diabetes. This is often the preferred drug to be used in combination with statins because of a reduced risk of negative drug interaction. It is taken once a day, usually with a meal.
- Clofibrate (Abitrate, Atromid-S). Sometimes also used in the treatment of a rare disorder called diabetes insipidus (“water diabetes”), in which the kidneys produce an abnormally large amount of diluted urine. However, clofibrate is also associated with increased risk of certain cancers, so it is rarely, if ever, prescribed.
Conditions of concern
Patients should discuss with their physician the benefits and risks of taking fibrates if they have any of the following factors:
- Liver disease (history of disease or persistently high liver enzymes). Use of fenofibrate may lead to worsening liver problems. In addition, use of clofibrate or gemfibrozil in patients with existing liver disease may result in a buildup of this drug in the bloodstream, increasing the potential for side effects.
- Kidney disease. This condition may lead to a buildup of fibrates in the bloodstream, increasing the potential for side effects and (in the case of fenofibrate) increasing the risk of worsening existing kidney problems.
- Gallbladder disease or gallstones. Fibrate use may lead to a worsening of these conditions.
- Ulcers of the stomach or intestines. Use of clofibrate may lead to a worsening of ulcers.
- Hypothyroidism (underactive thyroid gland). Use of clofibrate may complicate treatment of this condition.
- Increased homocysteine levels. Use of fenofibrate may raise the blood level of homocysteine, an amino acid produced as a normal byproduct of the breakdown of methionine, which is an essential (dietary) amino acid acquired mostly from eating meat and protein. High homocysteine levels have been linked to artery damage, which may increase the risk of heart attack, stroke or other cardiovascular problems. Research is ongoing to determine whether high homocysteine levels are an actual cause of those conditions, or are simply associated with them for some other reason. However, some physicians recommend patients taking fenofibrate also take folic acid, which lowers homocysteine levels.
- Heart transplant. Use of fibrates has been shown to affect the levels of cyclosporine, which could possibly lead to transplant rejection.
- Side effects
Potential side effects of fibrates
There are a number of side effects that could occur as a result of taking fibrates. Patients may experience an allergic reaction including sneezing, coughing, congestion or skin rashes. They also may develop muscle aches and abdominal pain with nausea and vomiting. Patients should immediately contact their physician if they experience these symptoms.
Other side effects associated with specific fibrates include:
- Fever or chills
- Fatigue, vertigo or headache
- Difficult or painful urination
- Nausea or vomiting
- Lower back or side pain
- Shortness of breath
- Skin rash or hives
- Sore throat
- Fever or chills
- Decreased sexual desire
- Dizziness or lightheadedness
- Sensitivity to light
- Eye irritations
- Shortness of breath
- Chest pain
- Palpitations or abnormal heartbeat
- Decreased urine or blood in urine
- Swelling (edema) of lower limbs
- Coughing or hoarseness
- Lower back or side pain
- Decreased sexual desire
- Lip or mouth sores
- Increased appetite or weight gain
A rare, but potentially fatal, side effect of fibrates is rhabdomyolysis. This is a condition in which muscle cells break down, releasing their contents into the bloodstream. It most often affects the muscles in the back or lower calves, although some patients report no symptoms. Rhabdomyolysis can lead to kidney or other organ failure and death. Risk of this severe complication appears to be higher in those fibrates used in conjunction with other cholesterol-reducing drugs called statins. One fibrate, fenofibrate, appears to have a lower risk of interacting with statins and is thus the preferred fibrate for combination therapy
Patients should report any of the following symptoms of rhabdomyolysis to their physicians immediately:
- Muscle cramps, pain, swelling, weakness, stiffness and/or tenderness
- Dark urine
- Nausea and/or vomiting
- Malaise (a general feeling of illness or discomfort)
In addition, some research suggests that taking fibrates, particularly clofibrate, may increase a person’s risk of developing cancer, pancreatitis (inflammation of the pancreas), gallstones and problems following gallbladder surgery. Patients are encouraged to discuss the potential risks and benefits of fibrates with their physicians.
Drug or other interactions
Patients should consult their physician before taking any other medication (either prescription or over-the-counter) or nutritional supplements. Of particular concern to patients taking fibrates are:
- Other cholesterol-reducing drugs. Taking more than one cholesterol reducer at a time may worsen side effects. Statins are of particular concern when taken in conjunction with fibrates such as gemfibrozil. The drug combination may increase the patient’s risk of developing a rare, but potentially fatal, reaction called rhabdomyolysis. Fenofibrate may also worsen some side effects, but is the preferred fibrate to combine with statins because of decreased risk of rhabdomyolysis.
- Anticoagulants. Medications that inhibit blood clot formation. Use with fibrates may increase the effects of anticoagulants and therefore increase the risk of bleeding. A physician may reduce the dose of anticoagulant when prescribing a fibrate.
- Immunosuppressants (e.g., cyclosporine). Medications used to suppress the body’s immune system that are often prescribed following an organ transplant (e.g. heart transplant) to prevent the body from rejecting the donor organ. Taking certain fibrates (fenofibrate) with immunosuppressants may increase an individual’s risk of developing or worsening kidney problems.
- Grapefruit juice.
Some fibrates (e.g., clofibrate) may result in stomach upset and should therefore be taken with food. Others should be taken before eating (e.g., gemfibrozil). Patients should carefully follow the directions for taking their medication provided by their physician and pharmacy. Those who miss a dose of this medication should take it as soon as possible, unless it is nearly time for the next dose. In that case, the missed dose should be skipped. Double doses of this medication should not be taken. Patients who are taking fibrates should receive regular check-ups to monitor their progress and cholesterol levels.
Fibrates may be less effective in people who are significantly overweight. Therefore, in addition to lifestyle changes recommended to reduce blood fat levels, patients may be placed on a weight loss program. In many cases, the lifestyle changes needed to manage blood fats will be similar to those in a weight loss program (e.g., diet, exercise, stress management).
Patients should not abruptly stop or change the dosage and timing of their medications without first consulting their physicians. It is also important that patients notify all physicians (including dentists) that they are taking fibrates before undergoing any surgical procedure.
Certain fibrates (e.g., fenofibrate) may increase an individual’s sensitivity to sunlight. Therefore, those taking these medications are encouraged to wear plenty of sunscreen (sun protection factor 15 or higher) and to take other precautions when spending time outdoors. Such measures include finding shade whenever possible, avoiding peak sunlight hours, staying covered with lightweight clothing and wearing a wide brimmed hat and sunglasses.
Most patients on medication to treat high cholesterol (hypercholesterolemia) will be taking it for the rest of their lives, provided no serious side effects occur. Patients should remember that medications may control high cholesterol, but they do not cure it. Even if all their symptoms are relieved, patients should continue to take their medication exactly as directed, eat a heart-healthy diet that is low in saturated fats and keep all scheduled follow-up appointments with their physician.
- How to use
Pregnancy use issues
Fibrate use during pregnancy has not been tested on humans, so it is not known for certain if fibrates impair fertility or cause harm to the fetus. Some animal studies have found that the use of certain fibrates during pregnancy increases the risk of fetal death, low birth weight and/or skeletal defects. This is why women taking fibrates should inform their physicians at once if they plan to – or believe they have – become pregnant.
A chemical component of fibrates is excreted in breast milk. These drugs, therefore, are not recommended for nursing mothers.
Child use issues
Clinical trials have not been conducted on the use and effectiveness of fibrates on children. Therefore, appropriate doses have not been determined for use by children, and the effectiveness of fibrates has not been compared to other cholesterol-reducing medications in children. Use is not recommended in children under age 2, because cholesterol is needed for normal body development.
Elderly use issues
Studies have shown that fibrates can benefit older adults with both coronary artery disease and low levels of HDL ("good") cholesterol. Fibrates have also demonstrated ability to lower triglyceride levels.
Questions for your doctorPatients may wish to ask their doctors or pharmacists the following questions about fibrates:
- How will fibrates help my cholesterol levels?
- Am I a candidate for fibrate treatment?
- If statins lower my cholesterol, what do fibrates do?
- Can I take statins and fibrates at the same time?
- Which fibrate drug is best for me?
- What are the side effects associated with this drug?
- Will the side effects eventually go away?
- What symptoms indicate the need for immediate medical attention?
- If this drug does not work, will you switch me to another fibrate?
- If I lower my bad cholesterol, will I still need to take fibrates?
- I have already had one heart attack, Will fibrates help prevent another?
- Do fibrates interact with my other medications or supplements I am taking?
- How will you monitor my progress?
- How often will I need to have my cholesterol levels checked?