Mechanism of action at molecular and tissue levels
The action of fibrates is based on the stimulation of peroxisome proliferator-activated nuclear receptors, namely PPARα. This triggers a cascade of reactions in the body:
- The expression of endothelial lipoprotein lipase, located on the vascular endothelium, is enhanced.
- The breakdown of triglyceride-rich particles—chylomicrons and VLDLs—is accelerated.
- The synthesis of Apo A proteins is activated, leading to an increase in protective high-density lipoproteins.
- The density of lipoprotein receptors on the surface of liver cells increases, while hepatic synthesis of cholesterol and VLDL is simultaneously suppressed.
Clinical use and group drugs
In modern medical practice, physicians use several main fibric acid derivatives: gemfibrozil, fenofibrate, bezafibrate, and ciprofibrate.
The main indications for their prescription are type II, IV, and V hyperlipidemias. The primary advantage of these agents is their ability to maximally reduce the concentration of triglycerides in the blood. For example, fenofibrate can reduce TG levels by 30–60% and total cholesterol by 16–35%. In addition, it possesses a useful uricosuric property, helping to excrete uric acid.
Pharmacokinetic properties and safety
Drugs in this group differ in elimination rate and metabolism:
- Gemfibrozil is well absorbed from the gastrointestinal tract, reaching peak concentration within 1–2 hours ($t_{1/2}$ is about 1.5 hours). It is excreted primarily by the kidneys.
- Fenofibrate acts as a prodrug, converting in tissues into active fenofibric acid. Its micronized form allows for once-daily dosing.
- Ciprofibrate features a record half-life ($t_{1/2}$ from 48 to 120 hours) and is taken once a day.
Safety: Adverse effects include dyspepsia, headaches, cholestasis, and dangerous toxic effects on muscle tissue (myalgia, myopathy, rarely rhabdomyolysis). Therefore, it is strictly prohibited to combine fibrates with statins to avoid cumulative toxic effects.
FibRATes take care of the vessels and strike at TRIglycerides (RAT clears the channel from the TRIo of fats).
Class and exam questions
Why should fibrates not be prescribed together with statins?
Simultaneous intake of fibrates and statins sharply increases the risk of severe myopathies due to the summation of adverse effects on muscle tissue.
What is the main laboratory manifestation of the efficacy of fibrates?
The main result of their intake is a pronounced decrease in blood triglyceride levels due to the activation of lipoprotein lipase.
What is the feature of fenofibrate as a dosage form?
Fenofibrate is a prodrug: upon entering tissues, it converts into active fenofibric acid, and its micronized form allows patients to take the drug just once a day.
What else to study on this topic
- Structure and role of PPARα receptors in lipid metabolism regulation
- Comparative analysis of the pharmacokinetics of gemfibrozil and ciprofibrate
- Biochemical transformations of VLDL into IDL and LDL
- Uricosuric effect of fenofibrate and its clinical significance
- Pathogenesis of drug-induced rhabdomyolysis in combination therapy
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