Fibric acid derivatives, or fibrates, are drugs prescribed to prevent heart disease by lowering triglyceride levels, though they are known as "cholesterol-lowering drugs", they are antilipemic agents. The drugs lower triglyceride levels as much as 25 to 50 percent according to WebMD, mainly by inhibiting the production of very low density lipoprotein (VLDL) in the liver and speeding up the removal of triglycerides from the blood. Lipoproteins transport insoluble fatty substances in the blood, including cholesterol and triglycerides; VLDL is the triglyceride-rich fraction. Triglycerides are fatty substances made up of three fatty acids and found in vegetable oil and animal fats. They play an important role in metabolism as they provide twice as much energy as carbohydrates and protein.
High circulating levels of triglycerides (hypertriglyceridemia) have been linked to atherosclerosis and heart disease, specifically the risk for coronary artery disease, and very high levels (>1000 mg/dl) can cause painful inflammation of the pancreas called pancreatitis. Fibrates are used to prevent pancreatitis and in conjunction with lifestyle changes (a low cholesterol and low-fat diet, exercise, smoking cessation) and statins to lower cholesterol. Fibric acid derivatives can not lower low density lipoprotein (LDL, also known as "bad" cholesterol) levels on their own, though they can increase high density lipoprotein (HDL, so-called "good" cholesterol) levels as much as 10 to 35 percent according to WebMD.
Fibrates activate peroxisome proliferator-activated receptors, known by their acronym PPAR, a group of intracellular receptors that activate the transcription of proteins used in lipid metabolism. Fibric acid derivatives mainly affect PPAR alpha, which is present in the liver and other tissues that metabolize fatty acids and is also involved in the inflammatory response in the blood vessel wall, an event associated with atherosclerosis. Fibrates are pharmacologically related to anti-diabetic drugs that also act on certain subtypes of PPAR. Fibrates in the United States include Lopid (gemfibrozil) and Tricor (fenofibrate). Gemfibrozil has been shown to decrease the risk of heart attack in individuals with coronary artery disease and low HDL levels.
Most patients tolerate fibric acid derivatives well, but like any other pharmaceutical treatment they can have side effects. Gastrointestinal pain and discomfort, headache, and gas or heartburn are common, but a doctor should be contacted if muscle pain, nausea or vomiting, fever, weakness, severe abdominal pain, or signs of allergy (hives, trouble breathing, swelling) occur. Patients on fibrates also have an increased risk of gallstones, which are small, hard accumulations of cholesterol in the gall bladder. Fibrates may alter the function of other medications, so your doctor should be aware of all other prescriptions and over the counter drugs you take.