Fibrates

Verified · Oct 2026

Prototype: fenofibrate

Fibrates are a class of medications used with diet to lower very high triglyceride levels.

Medical view → mechanisms, drug comparisons and Step 1 pharmacology

Fenofibrate and gemfibrozil speed the clearance of triglyceride-rich particles. Their catches: myopathy and rhabdomyolysis with statins (gemfibrozil most), gallstones, liver and kidney effects, and a stronger warfarin effect.

How it works in the body

The system involved, what goes wrong, and how the drug and body interact.

01 Lowering triglycerides through PPAR-α

Fenofibrate is a prodrug: esterases turn it into fenofibric acid, which activates the nuclear receptor PPAR-α. That activates lipoprotein lipase and reduces apolipoprotein C-III (an inhibitor of lipoprotein lipase), so triglyceride-rich particles are broken down and cleared from plasma faster. Gemfibrozil’s mechanism is less clearly established: it inhibits peripheral lipolysis and hepatic uptake of free fatty acids, cutting hepatic triglyceride production, and it lowers VLDL output.

The main effect is a fall in triglycerides and VLDL; both drugs also raise HDL. LDL changes less predictably — in patients with very high triglycerides it can even rise. Fenofibrate did not reduce coronary heart disease events or deaths in two large trials in type 2 diabetes, so fibrates are used mainly for triglycerides, as an add-on to diet. The -fibrate stem marks clofibrate derivatives (PPAR-α agonists); gemfibrozil is listed by WHO only as a related name.

Loading diagram…

Fibrates activate PPAR-α, speeding the breakdown of triglyceride-rich particles.

02 Why gemfibrozil and statins do not mix

Any fibrate can cause myopathy, and the risk of rhabdomyolysis rises when a fibrate is added to a statin. Gemfibrozil adds a pharmacokinetic problem: it inhibits OATP1B1, a transporter that many statins are substrates of, so statin exposure climbs; it is also a strong CYP2C8 inhibitor. Gemfibrozil with simvastatin is contraindicated, rosuvastatin should be avoided, and the label says combined therapy can lead to severe myopathy, rhabdomyolysis and acute renal failure.

Its other contraindicated pairs also rest on raised exposure: repaglinide (an OATP1B1 substrate; exposure rises about 8-fold, with severe hypoglycemia), dasabuvir (CYP2C8 inhibition; QT risk) and selexipag (its active metabolite rises about 11-fold). Fenofibrate with a statin is not contraindicated, but its label says to avoid the combination unless further triglyceride lowering is likely to outweigh the added risk.

Loading diagram…

Gemfibrozil blocks OATP1B1 and CYP2C8, raising levels of statins and other drugs.

03 Gallbladder, liver, kidney and blood

Fibrates may increase cholesterol excretion into bile, leading to gallstones; pre-existing gallbladder disease is a contraindication, and the drug is stopped if gallstones are found. Pancreatitis has also been reported with fenofibrate.

Fenofibrate can cause drug-induced liver injury (including cases leading to transplantation or death) and rises in serum creatinine; fenofibric acid is cleared mainly by the kidney, so severe renal impairment is a contraindication. Gemfibrozil can worsen renal insufficiency when baseline creatinine is above 2.0 mg/dL. Both can lower hemoglobin, hematocrit and white cells early on, and both potentiate warfarin.

Drug names

Generic Brand

fenofibrate Antara, Lipofen

gemfibrozil Lopid

Indications

Fenofibrate and gemfibrozil as adjuncts to diet for severe hypertriglyceridemia (fenofibrate: TG ≥ 500 mg/dL; gemfibrozil: Types IV and V hyperlipidemia with a risk of pancreatitis)
Fenofibrate to lower elevated LDL-C in primary hyperlipidemia when recommended LDL-lowering therapy is not possible
Gemfibrozil to reduce coronary heart disease risk only in Type IIb patients without coronary disease (low HDL with high LDL and triglycerides; inadequate response to other measures)

Mechanism of action

Fenofibrate is hydrolyzed to fenofibric acid, a PPAR-α agonist that activates lipoprotein lipase and reduces apolipoprotein C-III production, increasing lipolysis and clearance of triglyceride-rich particles. Gemfibrozil inhibits peripheral lipolysis and hepatic free-fatty-acid extraction, reducing hepatic triglyceride production, and inhibits synthesis and increases clearance of VLDL apolipoprotein B.

In plain terms

They switch on a liver “fat-burning” control so the body clears triglyceride-laden particles from the blood faster.

Therapeutic effects — what you'll see working

Fibrates are added to a lipid-lowering diet, not used instead of it. Success is a lower triglyceride level; if the lipid response is inadequate after 2 months (fenofibrate) or 3 months (gemfibrozil), the drug is stopped.

↓ Triglycerides and VLDL ↑ HDL

↓ Triglycerides and VLDL: The main effect: fenofibric acid lowers total triglycerides and triglyceride-rich VLDL; gemfibrozil reduces hepatic triglyceride and VLDL production.
↑ HDL: Fenofibrate raised HDL-cholesterol in its trials, and gemfibrozil raises HDL-cholesterol and apolipoproteins AI and AII; LDL changes are variable and may rise in patients with very high triglycerides.

Adverse effects

Watch the muscles (especially with a statin), the gallbladder, the liver and the kidneys — and the INR in anyone on warfarin.

Common

Abnormal liver tests, abdominal pain, raised CK and constipation (fenofibrate); dyspepsia, abdominal pain and diarrhea (gemfibrozil).

Rising liver tests were the most frequent reason fenofibrate was stopped in trials. Gemfibrozil’s gastrointestinal reactions (mainly dyspepsia and abdominal pain) occurred in about a third of patients in the Helsinki Heart Study.

Myopathy and rhabdomyolysis Hold & notify

Muscle pain, tenderness or weakness with raised CK — rhabdomyolysis can follow, especially with a statin.

Risk rises with age 65 or older, uncontrolled hypothyroidism, renal impairment, statins and colchicine. With gemfibrozil plus a statin, rhabdomyolysis has led to acute renal failure and death, sometimes within three weeks of starting. Stop the fibrate if CK is markedly raised or myopathy is suspected.

Liver injury Hold & notify

Serious drug-induced liver injury with fenofibrate; raised liver tests with gemfibrozil.

Fenofibrate liver injury has appeared within weeks or after months — dark urine, jaundice, abdominal pain, malaise, pruritus — and has led to transplantation or death. It is stopped if ALT or AST stays above 3 times the upper limit of normal or bilirubin rises, and not restarted without another explanation. Gemfibrozil liver-test changes usually reverse on stopping.

Gallstones and pancreatitis Hold & notify

Gallstones (cholelithiasis) with either fibrate; pancreatitis reported with fenofibrate.

If gallstones are suspected, gallbladder studies are done and the fibrate is stopped if stones are found. Pancreatitis may reflect treatment failure in severe hypertriglyceridemia, a direct drug effect, or stones or sludge obstructing the common bile duct.

Kidney effects

Rises in serum creatinine with fenofibrate; worsening renal insufficiency with gemfibrozil.

Fenofibrate creatinine rises tend to reverse after stopping; monitor renal function in renal impairment and consider it in older or diabetic patients. Gemfibrozil has worsened renal insufficiency when baseline creatinine was above 2.0 mg/dL.

Hypersensitivity (fenofibrate) Report immediately

Anaphylaxis, angioedema and severe skin reactions (SJS, TEN, DRESS) with fenofibrate.

Acute reactions can be life-threatening; severe cutaneous reactions occur days to weeks after starting. Stop fenofibrate and treat.

Blood counts, HDL and clots

Early falls in hemoglobin, hematocrit and white cells (both); paradoxical HDL fall and more venous thromboembolism (fenofibrate).

Blood counts usually stabilize; thrombocytopenia and agranulocytosis are rare. A severe paradoxical fall in HDL-C means stopping fenofibrate permanently. In the FIELD trial, pulmonary embolism and DVT were more frequent with fenofibrate.

Interactions

Statins drug

More myopathy and rhabdomyolysis. Gemfibrozil + simvastatin is contraindicated and gemfibrozil + rosuvastatin should be avoided; fenofibrate + a statin only if the benefit outweighs the risk, with monitoring for muscle symptoms.

Repaglinide (gemfibrozil) drug

Contraindicated — repaglinide exposure rises about 8-fold, with prolonged, severe hypoglycemia.

Warfarin and other coumarin anticoagulants drug

Fibrates potentiate the anticoagulant effect and prolong the PT/INR — the warfarin dose is reduced and the INR checked frequently until stable.

Colchicine drug

Adds to myopathy risk, especially in older patients or those with renal dysfunction.

CYP2C8 and OATP1B1 substrates (gemfibrozil) drug

Gemfibrozil raises their levels — for example pioglitazone, montelukast and paclitaxel (CYP2C8), and glyburide and ezetimibe (OATP1B1); dasabuvir and selexipag are contraindicated.

Bile-acid binding resins drug

Bind fibrates in the gut — give fenofibrate at least 1 hour before or 4–6 hours after the resin, and gemfibrozil at least 2 hours apart.

Cyclosporine, tacrolimus and other nephrotoxic drugs (fenofibrate) drug

Risk of worsening renal function, since fibrates are cleared by the kidney — monitor renal function.

Contraindications

The contraindications protect the organs fibrates stress — kidney, liver and gallbladder — and block gemfibrozil’s dangerous drug pairs.

Severe renal impairment (fenofibrate: including end-stage renal disease and dialysis; gemfibrozil: severe renal dysfunction)

Labeled contraindications — fibrates are cleared mainly by the kidney.

Active liver disease or unexplained persistent liver-test abnormalities (fenofibrate); hepatic dysfunction including primary biliary cirrhosis (gemfibrozil)

Labeled contraindications — fibrates can injure the liver.

Pre-existing gallbladder disease

Labeled contraindication for both drugs — fibrates can cause gallstones.

Gemfibrozil with simvastatin, repaglinide, dasabuvir or selexipag

Labeled contraindications — gemfibrozil raises their exposure (OATP1B1: simvastatin, repaglinide; CYP2C8: dasabuvir; selexipag’s active metabolite about 11-fold), with rhabdomyolysis, severe hypoglycemia or QT prolongation as the risks.

A fibrate with a statin (other than gemfibrozil with simvastatin) use caution

Not contraindicated, but the risk of myopathy and rhabdomyolysis rises; avoid unless the benefit clearly outweighs it (avoid gemfibrozil with rosuvastatin).

Breastfeeding use caution

Fenofibrate is likely present in human milk and could disrupt infant lipid metabolism, so breastfeeding is avoided during Antara treatment and for 5 days after the last dose; with gemfibrozil, either nursing or the drug is stopped.

When to hold

Assess before giving — these findings mean hold the dose and act.

Unexplained muscle pain, tenderness or weakness, especially with fever or malaise

Hold and notify — check CK; the fibrate is stopped if CK is markedly raised or myopathy is suspected.

Signs of liver injury (jaundice, dark urine, abdominal pain), or ALT/AST persistently above 3 times the upper limit of normal

Hold and notify — fenofibrate is stopped and not restarted without another explanation.

Right-upper-quadrant pain or suspected gallstones, or severe abdominal pain

Notify the prescriber — gallbladder studies; the fibrate is stopped if gallstones are found; pancreatitis has also been reported.

Acute serious illness with a high risk of renal failure from rhabdomyolysis (sepsis, shock, severe hypovolemia, major surgery, trauma)

Hold and notify — fenofibrate is temporarily stopped.

Labs & levels

Test Therapeutic / normal Toxic / critical

Liver function (ALT, AST, bilirubin) Baseline and periodically (fenofibrate); periodically (gemfibrozil) — ALT or AST persistently > 3 × ULN, or with a rising bilirubin → stop fenofibrate

Renal function (serum creatinine / eGFR) Before fenofibrate and periodically, especially in renal impairment, older or diabetic patients — eGFR < 30 → fenofibrate contraindicated; gemfibrozil has worsened renal insufficiency when creatinine is above 2.0 mg/dL

Creatine kinase (CK) If muscle pain, tenderness or weakness develops — Markedly elevated, or myopathy suspected → stop the fibrate

CBC Periodically during the first 12 months — —

Lipids (triglycerides and HDL-C) Triglycerides 4–8 weeks after starting fenofibrate; HDL-C within the first few months (paradoxical fall); stop if no adequate response after 2 months (fenofibrate) or 3 months (gemfibrozil) — —

PT/INR (with warfarin) Frequently until stable after a fibrate is added — —

Nursing considerations

The RN-specific layer — each action paired with the reason it matters.

Both fibrates

Review the medication list for statins, colchicine, warfarin and bile-acid resins; teach the patient to report unexplained muscle pain, tenderness or weakness, especially with fever or malaise.

Why: These combinations raise the risk of myopathy and rhabdomyolysis or change the INR, and resins block absorption.

Check liver function, renal function and blood counts as ordered, and report right-upper-quadrant or severe abdominal pain.

Why: Fibrates can injure the liver, raise creatinine, lower blood counts early on, and cause gallstones or pancreatitis.

Reinforce the lipid-lowering diet, weight loss and limiting alcohol.

Why: Fibrates are adjuncts to diet; excess weight and alcohol worsen hypertriglyceridemia.

Fenofibrate

Give once daily — Antara with or without food, Lipofen with food; the capsules are swallowed whole, not crushed or chewed.

Why: Food needs differ by formulation: Antara may be taken with or without food, while Lipofen is given with food, which increases its absorption; both labels require whole capsules.

Teach the patient to seek emergency care for facial or throat swelling, hives or a spreading rash, and to report dark urine or yellowing of the skin.

Why: Fenofibrate can cause anaphylaxis, angioedema, severe skin reactions and drug-induced liver injury.

Gemfibrozil

Give 30 minutes before the morning and evening meals.

Why: Absorption is faster and greater when gemfibrozil is taken half an hour before meals.

Confirm the patient is not taking simvastatin, repaglinide, dasabuvir or selexipag.

Why: These combinations are contraindicated — gemfibrozil raises their levels (rhabdomyolysis with simvastatin, severe hypoglycemia with repaglinide).

Common questions

What are Fibrates used for?

Fenofibrate and gemfibrozil as adjuncts to diet for severe hypertriglyceridemia. Fenofibrate to lower elevated LDL-C in primary hyperlipidemia when recommended LDL-lowering therapy is not possible. Gemfibrozil to reduce coronary heart disease risk only in Type IIb patients without coronary disease.

How do Fibrates work?

They switch on a liver “fat-burning” control so the body clears triglyceride-laden particles from the blood faster.

What are the serious side effects of Fibrates?

Watch for muscle pain, tenderness or weakness with raised CK — rhabdomyolysis can follow, especially with a statin; serious drug-induced liver injury with fenofibrate; raised liver tests with gemfibrozil; gallstones (cholelithiasis) with either fibrate; pancreatitis reported with fenofibrate.

When should a nurse hold Fibrates, and what safety checks apply?

Unexplained muscle pain, tenderness or weakness, especially with fever or malaise: hold and notify — check CK; the fibrate is stopped if CK is markedly raised or myopathy is suspected. Signs of liver injury (jaundice, dark urine, abdominal pain), or ALT/AST persistently above 3 times the upper limit of normal: hold and notify — fenofibrate is stopped and not restarted without another explanation. Right-upper-quadrant pain or suspected gallstones, or severe abdominal pain: notify the prescriber — gallbladder studies; the fibrate is stopped if gallstones are found; pancreatitis has also been reported. Acute serious illness with a high risk of renal failure from rhabdomyolysis (sepsis, shock, severe hypovolemia, major surgery, trauma): hold and notify — fenofibrate is temporarily stopped.

What labs should be monitored with Fibrates?

Monitor liver function (ALT, AST, bilirubin), renal function (serum creatinine / eGFR), creatine kinase (CK), CBC, lipids (triglycerides and HDL-C), and PT/INR (with warfarin).

Sources

Reviewed by Hae Suk Lee, RN

Educational summary for nursing students. Always verify against current prescribing information and your institution's protocols before administering. Not medical advice.