Antilipidemic Drugs

Familial hypercholesterolemia is caused primarily by loss-of-function mutations in the low-density lipoprotein receptor gene, accounting for about 85 to 90 percent of genetically confirmed cases. Less common causes include gain-of-function mutations in proprotein convertase subtilisin/kexin type 9 and loss-of-function mutations in apolipoprotein B. The heterozygous form produces untreated low-density lipoprotein cholesterol typically in the range of 190 to 400 milligrams per deciliter, with cardiovascular events often occurring in the fourth and fifth decades of life if untreated.

Clinical features that should trigger consideration of familial hypercholesterolemia include: low-density lipoprotein cholesterol persistently above 190 milligrams per deciliter in an adult; tendon xanthomas (firm cholesterol deposits in the Achilles or hand tendons); premature atherosclerotic cardiovascular disease in a first-degree relative (men below 55 years, women below 60 years); and a family history of elevated cholesterol. A practical clinical rule is that any adult with untreated low-density lipoprotein cholesterol above 190 milligrams per deciliter should be evaluated for familial hypercholesterolemia before starting therapy. Genetic testing confirms the diagnosis and enables cascade screening of first-degree relatives — identifying at-risk family members before cardiovascular events occur is the single most cost-effective intervention in familial hypercholesterolemia management.

All patients with heterozygous familial hypercholesterolemia require high-intensity statin therapy, initiated as early as childhood in affected patients (from around age 8 to 10 years). Because even high-intensity statin rarely achieves adequate low-density lipoprotein cholesterol reduction from a starting point of 250 to 350 milligrams per deciliter, most heterozygous familial hypercholesterolemia patients require combination therapy. The standard escalation is: high-intensity statin, then add ezetimibe, then add a proprotein convertase subtilisin/kexin type 9 inhibitor (evolocumab or alirocumab) if still not at target. This triple combination can reduce low-density lipoprotein cholesterol by 70 to 85 percent from untreated baseline.

Homozygous familial hypercholesterolemia is rare (approximately one in 300,000 to one million individuals) but severe. Untreated low-density lipoprotein cholesterol is typically 400 to 1,000 milligrams per deciliter, with xanthomas, corneal arcus, and aortic stenosis often appearing in childhood. Without aggressive treatment, coronary atherosclerosis can produce fatal events in the second or third decade of life.

Statins and ezetimibe work primarily by upregulating low-density lipoprotein receptor expression. In homozygous familial hypercholesterolemia, patients carry two mutant low-density lipoprotein receptor alleles with severely reduced or absent receptor function, so these drugs produce only 10 to 25 percent low-density lipoprotein cholesterol reduction rather than the 60 to 65 percent seen in patients with normal receptors. Proprotein convertase subtilisin/kexin type 9 inhibitors prevent degradation of low-density lipoprotein receptors — but if the receptors are absent or non-functional, there is nothing to protect. Monoclonal antibody proprotein convertase subtilisin/kexin type 9 inhibitors have markedly attenuated efficacy in true receptor-negative homozygous familial hypercholesterolemia.

Two agents approved specifically for homozygous familial hypercholesterolemia work through low-density lipoprotein receptor-independent pathways. Lomitapide blocks the assembly of apolipoprotein B-containing lipoproteins in the liver and intestine before they are secreted into the bloodstream, reducing low-density lipoprotein cholesterol production regardless of receptor status. Evinacumab is a monoclonal antibody targeting angiopoietin-like protein 3, an inhibitor of lipoprotein lipase; blocking it enhances triglyceride-rich lipoprotein clearance through a receptor-independent pathway. Both agents produce approximately 40 to 50 percent additional low-density lipoprotein cholesterol reduction in homozygous familial hypercholesterolemia patients on maximal background therapy, including those with no functional low-density lipoprotein receptors.

The clinical approach to elevated triglycerides depends on the absolute level, because the therapeutic goal changes at different thresholds.

For moderate hypertriglyceridemia (135 to 499 milligrams per deciliter) in patients already on statin therapy with established atherosclerotic cardiovascular disease or diabetes with additional risk factors, the therapeutic goal is cardiovascular event reduction. Icosapentaenoic acid ethyl ester 4 grams per day is the agent of choice in this range, with an American College of Cardiology/American Heart Association Class IIa recommendation based on proven cardiovascular outcomes. Fibrates do not reduce cardiovascular events in this triglyceride range on background statin and are not indicated for this goal.

For severe hypertriglyceridemia (above 500 milligrams per deciliter), the primary goal shifts to pancreatitis prevention. At levels above 1,000 milligrams per deciliter, the risk of acute pancreatitis is substantial and immediate. First-line management is fenofibrate combined with a very-low-fat diet, alcohol cessation, and correction of secondary causes (uncontrolled diabetes, hypothyroidism, medications including corticosteroids and oral estrogens). Icosapentaenoic acid ethyl ester may be added once triglycerides fall below 500 milligrams per deciliter.

Type 2 diabetes produces a characteristic dyslipidemia triad driven by insulin resistance: elevated triglycerides, low high-density lipoprotein cholesterol, and a predominance of small dense low-density lipoprotein particles. The measured low-density lipoprotein cholesterol may be normal or only modestly elevated while atherogenic particle burden (measured by apolipoprotein B or non-high-density lipoprotein cholesterol) is substantially higher than the low-density lipoprotein cholesterol number suggests. This makes non-high-density lipoprotein cholesterol and apolipoprotein B more relevant treatment targets than low-density lipoprotein cholesterol alone in diabetic patients.

Statin therapy is the foundation of lipid management in all patients with type 2 diabetes aged 40 to 75. At least moderate-intensity statin is indicated for all; high-intensity statin is appropriate for those with established atherosclerotic cardiovascular disease or a high ten-year risk. The statin-associated new-onset diabetes risk discussed in Module 3 is not a contraindication in patients who already have diabetes.

For diabetic patients with residual triglyceride elevation on statin therapy (135 to 499 milligrams per deciliter), icosapentaenoic acid ethyl ester 4 grams per day is appropriate given the American College of Cardiology/American Heart Association Class IIa indication for this population. Glucagon-like peptide-1 receptor agonists (such as semaglutide) and sodium-glucose cotransporter-2 inhibitors (such as empagliflozin) also modestly reduce triglycerides through improved insulin sensitivity and have established cardiovascular outcome benefits in diabetes.

Chronic kidney disease produces a distinctive dyslipidemia with elevated triglycerides, low high-density lipoprotein cholesterol, and a predominance of small dense low-density lipoprotein particles, resulting in substantially elevated cardiovascular risk at any given low-density lipoprotein cholesterol level. The definitive randomized trial enrolled over nine thousand patients with chronic kidney disease and demonstrated that statin plus ezetimibe reduced major atherosclerotic events by approximately 17 percent in pre-dialysis patients over five years. The benefit was not seen in the dialysis subgroup, consistent with findings from two prior dedicated dialysis trials that also found no cardiovascular event reduction.

The likely explanation for the dialysis paradox mirrors the heart failure statin paradox: in end-stage kidney disease on dialysis, cardiovascular deaths occur predominantly from uremic cardiomyopathy, arrhythmia, and sudden cardiac death rather than from atherosclerotic plaque rupture — mechanisms not prevented by lipid lowering.

Atorvastatin is generally the preferred high-intensity statin in chronic kidney disease because it undergoes minimal renal excretion (less than two percent of drug is excreted unchanged in urine) and does not require dose adjustment. Rosuvastatin undergoes proportionally greater renal excretion and accumulates in severe chronic kidney disease; the dose should be capped at 10 milligrams per day when estimated glomerular filtration rate falls below 30 milliliters per minute per 1.73 square meters.

Ezetimibe requires no dose adjustment in chronic kidney disease and is an appropriate add-on agent at any stage. Proprotein convertase subtilisin/kexin type 9 inhibitors also require no dose adjustment and have been shown to be effective and safe in chronic kidney disease patients enrolled in the major outcomes trials.

Fenofibrate should be used cautiously in chronic kidney disease. It causes a reversible rise in serum creatinine through reduced tubular secretion (not nephrotoxicity), which can confuse monitoring. More importantly, fenofibrate accumulates in severe chronic kidney disease, increasing myopathy risk. It should be avoided when estimated glomerular filtration rate is below 30 milliliters per minute per 1.73 square meters and used at reduced doses when estimated glomerular filtration rate is 30 to 60 milliliters per minute per 1.73 square meters.