When a balanced diet, combined with a regular program of physical activity, is not enough to restore the values of cholesterol and triglycerides in the blood, it is necessary to intervene with specific drugs.
These include statins, ezetimibe and, in fact, fibrates (clofibrate, bezafibrate, gemfibrozil, fenofibrate).
Mechanism of action
Fibrates carry out their lipid-lowering activity by acting at different levels. The main mechanism of action concerns the stimulation on the catabolism of VLDL (lipoprotein particles used to transport triglycerides, and to a lesser extent cholesterol, in the blood). This activity is mediated by the activation of the lipoprotein lipase or LPL (a plasma enzyme that hydrolyzes circulating triglycerides).
In addition to increasing the rate at which they are removed from the circulation, fibrates reduce the synthesis of VLDL in the liver.
As for cholesterol, this class of drugs facilitates biliary elimination and blocks the activity of HMG-CoA-reductase (a liver enzyme responsible for the production of cholesterol). The stimulation of the fibrates on the synthesis of Apo A1 lipoprotein, also allows to slightly raise the levels of good cholesterol.
Effectiveness
Fibrates lower cholesterol levels to a lesser extent than statins, but have been shown to be more effective in decreasing plasma triglyceride levels. Taken in the form of tablets or capsules, they increase good HDL cholesterol by 10-15%, while the reduction in triglycerides settles on average around 40-45%. Fibrates can also contribute to the reduction of LDL-cholesterol levels, from 5 to a maximum of 18 percentage points.
Some fibrates (bezafibrate and fenofibrate) reduce the plasma concentration of fibrinogen, a protein involved in the blood clotting process. By reducing fibrinogenemia and platelet aggregation, these fibrates decrease blood density, making it even less prone to thrombus formation (clots that form in vessels and are very dangerous for health).
Doses of intake
200 to 900 mg / day, depending on the molecule.
Side effects
In general, fibrates are well tolerated when taken alone, although they can cause minor gastrointestinal disorders. Their efficacy and safety has been extensively studied and consolidated over time, since they have been in therapy for several years now (clofibrate was introduced in the clinic in 1962).
Since fibrates are eliminated almost completely by the kidney, they should be administered in reduced doses in patients suffering from renal insufficiency. Particular caution also in the presence of liver diseases and in the simultaneous intake of toxic substances for the liver (including alcohol!). For this reason, even healthy patients treated with fibrates should check the health of their liver every six months, undergoing simple blood tests (transaminase dosage + blood count).
Rarer side effects concern skin rashes and impotence; some fibrates, due to an increase in the saturation of cholesterol contained in it, make the bile more likely to form stones.
Only for people suffering from particularly severe hyperlipidemias is the simultaneous intake of statins and fibrates proposed, and in any case for a limited time. This combination in fact significantly elevates the adverse effects of the two drugs, which recognize two common side effects in liver toxicity and the appearance of pain and muscle tension.
Fibrates should not be taken during pregnancy and breastfeeding.
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