Comprehensive Overview of Hyperlipidemia and Antihyperlipidemic Drug Classes

Comprehensive Overview of Hyperlipidemia and Antihyperlipidemic Drug Classes

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  Mr. SATENDRA PRADHAN AssistantProfessor Department of Pharmacology COP, SVITS, Bilaspur & Mr. SATENDRA PRADHAN Assistant Professor Department of Pharmacology COP, SVITS, Bilaspur Dr. SREEJA PA Professor & Head Department of Pharmacy Practice Dr. MGR University, Chennai
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  INTRODUCTION What Is Hyperlipidemia Definition Hyperlipidemiais a metabolic disorder characterized by abnormally elevated levels of lipids (fats) in the blood, including cholesterol and/or triglycerides. Clinical Significance It is a major, modifiable risk factor for atherosclerotic cardiovascular disease (ASCVD): coronary artery disease, stroke, and peripheral arterial disease. Normal Lipid Targets (adult) Lipid Parameter Normal Level Total Cholesterol < 200 mg/dL LDL ("Bad" cholesterol) < 100 mg/dL HDL ("Good" cholesterol) > 40 mg/dL (men), > 50 mg/dL (women) Triglycerides < 150 mg/dL
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  THE BASICS Lipoproteins Chylomicrons Chylomicrons arethe largest and least dense lipoproteins. They transport dietary (exogenous) triglycerides and cholesterol from the intestine to peripheral tissues and the liver. Main Composition- Triglycerides (85–90%) Small amounts of cholesterol, phospholipids, and proteins VLDL (Very Low-Density Lipoprotein) Very-low-density lipoprotein. VLDL transports endogenous (liver-produced) triglycerides from the liver to peripheral tissues. Main Composition- Triglycerides (50–65%) LDL (Low-Density Lipoprotein ) LDL is known as "Bad Cholesterol" because it delivers cholesterol from the liver to peripheral tissues. Main Composition- Cholesterol and cholesterol esters HDL (High-Density Lipoprotein) HDL is known as "Good Cholesterol" because it removes excess cholesterol from tissues and transports it back to the liver (reverse cholesterol transport). Triglycerides (TG) Triglycerides are the main storage form of fat in the body and provide a major source of energy. Lipoprotein Site of Formation Major Lipid Carried Main Function Clinical Name Chylomicrons Intestine Dietary triglycerides Transport dietary fat to tissues Largest lipoprotein VLDL Liver Endogenous triglycerides Transport liver-made triglycerides Triglyceride carrier LDL From VLDL Cholesterol Deliver cholesterol to tissues Bad cholesterol HDL Liver & intestine Cholesterol Remove cholesterol from tissues to liver Good cholesterol
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  CLASSIFICATION Types of Hyperlipidemia Primary(Familial) Genetic/inherited defects in lipid metabolism - e.g. Familial Hypercholesterolemia (LDL-receptor mutation), Familial Combined Hyperlipidemia, Familial Hypertriglyceridemia. Secondary (Acquired) Result of another condition or lifestyle factor - diabetes mellitus, hypothyroidism, nephrotic syndrome, obesity, alcohol excess, or drugs (steroids, thiazides, beta-blockers). Fredrickson / WHO Phenotype Classification Type Elevated Particle Lipid Abnormality I Chylomicrons ↑↑ Triglycerides IIa LDL ↑ Cholesterol IIb LDL + VLDL ↑ Cholesterol + ↑ Triglycerides III IDL (remnants) ↑ Cholesterol + ↑ Triglycerides IV VLDL ↑ Triglycerides V VLDL + Chylomicrons ↑↑ Triglycerides + ↑ Cholesterol
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  ETIOLOGY Causes & RiskFactors Genetic Family history of premature ASCVD; inherited LDL- receptor or Apo-B/Apo-E defects. Dietary • High intake of saturated/trans fats • Excess refined carbohydrates and alcohol. Metabolic Disease • Diabetes mellitus • Hypothyroidism • Obesity • Metabolic syndrome. Renal / Hepatic Disease • Nephrotic syndrome • Chronic kidney disease • Cholestatic liver disease. Drug-Induced • Corticosteroids • Thiazide diuretics • Non-selective beta-blockers • Oral estrogens • Protease inhibitors. Lifestyle • Sedentary behaviour • Smoking • Excess body weight worsen the lipid profile.
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  PATHOPHYSIOLOGY From Hyperlipidemia toAtherosclerosis Chronic elevation of plasma LDL-cholesterol LDL infiltrates and is retained in the arterial sub-endothelial space LDL undergoes oxidative modification (oxLDL) Monocytes are recruited, become macrophages, engulf oxLDL → foam cells Foam cells + smooth-muscle proliferation form a fatty streak → atheromatous plaque PLAQUE RUPTURE/THROMBOSIS → MI, STROKE, PERIPHERALARTERIAL DISEASE WHY THIS WORKS This cascade is the pharmacological rationale for treating hyperlipidemia: every antihyperlipidemic drug class ultimately aims to break this chain by lowering circulating LDL-C, raising HDL-C, or lowering triglycerides - reducing the substrate available for plaque formation.
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  Drug Classification Classification ofAntihyperlipidemic Drugs
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  SIX MAJOR CLASSES Classificationat a Glance 1. HMG-CoA Reductase Inhibitors (Statins) Atorvastatin, Rosuvastatin, Simvastatin, Pravastatin first-line LDL-lowering agents. 2. Fibric Acid Derivatives (Fibrates) Fenofibrate, Gemfibrozil, Bezafibrate most potent triglyceride-lowering agents. 3. Bile Acid Sequestrants (Resins) Cholestyramine, Colestipol, Colesevelam bind intestinal bile acids. 4. Niacin (Nicotinic Acid) Best agent for raising HDL-cholesterol; also lowers LDL and triglycerides. 5. Cholesterol Absorption Inhibitor Ezetimibe blocks intestinal NPC1L1 transporter; complements statins. 6. PCSK9 Inhibitors Evolocumab, Alirocumab, Inclisiran injectable agents with the largest LDL reduction.
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  CLASS 1 ·STATINS HMG-CoA Reductase Inhibitors - Mechanism of Action Statin binds and competitively inhibits HMG-CoA reductase in hepatocytes Blocks conversion of HMG-CoA to mevalonate (rate-limiting step of cholesterol synthesis) Hepatic intracellular cholesterol synthesis falls Compensatory upregulation of SREBP-2 → more LDL receptors expressed on hepatocyte surface Hepatic uptake of circulating LDL particles increases ↓↓ Plasma LDL-C and total cholesterol, ↓ triglycerides, mild ↑ HDL-C WHY THIS WORKS HMG-CoA reductase catalyses the rate- limiting step of the mevalonate pathway. Inhibiting it lowers intracellular cholesterol, which triggers SREBP-2-mediated transcription of the LDL-receptor gene. This explains why statins are the most effective class for LDL-C reduction and why the effect is dose- and potency- dependent. Examples: Atorvastatin, Rosuvastatin
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  HMG-CoA Reductase Inhibitors- Uses & Adverse Effects Examples: Atorvastatin, Rosuvastatin, Simvastatin, Pravastatin, Fluvastatin Therapeutic Uses ✦ Primary prevention of atherosclerotic cardiovascular disease (ASCVD) in high-risk patients ✦ Secondary prevention after MI, stroke, or revascularization ✦ Primary hypercholesterolemia and mixed dyslipidemia ✦ Diabetic dyslipidemia and familial hypercholesterolemia (with other agents) Adverse Effects ✦ Myopathy – myalgia to rhabdomyolysis (↑ CPK) ✦ Hepatotoxicity – transaminase elevation ✦ New-onset type 2 diabetes mellitus (small risk) ✦ GI upset, headache; rare peripheral neuropathy
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  CLASS 2 ·FIBRATES Fibric Acid Derivatives - Mechanism of Action Fibrate activates PPAR-alpha, a nuclear transcription factor, in liver and muscle PPAR-alpha activation increases lipoprotein lipase (LPL) gene expression and decreases Apo C-III (an LPL inhibitor) Increased LPL activity accelerates hydrolysis of triglycerides in VLDL and chylomicrons PPAR-alpha also boosts hepatic fatty-acid oxidation and reduces hepatic VLDL (triglyceride) production Apo A-I and A-II synthesis increase, raising HDL particle formation ↓↓ Plasma triglycerides, ↑ HDL-C, modest ↓ LDL-C WHY THIS WORKS PPAR-alpha is a master transcriptional regulator of genes controlling fatty-acid and lipoprotein metabolism. Because fibrates act mainly on triglyceride-rich lipoproteins (via LPL and Apo C-III), they are the most potent class for lowering triglycerides - explaining their preferred use in severe hypertriglyceridemia to prevent pancreatitis. Example: Fenofibrate, Gemfibrozil
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  Fibric Acid Derivatives- Uses & Adverse Effects Examples: Fenofibrate, Gemfibrozil, Bezafibrate, Ciprofibrate Therapeutic Uses ✦ Severe hypertriglyceridemia (>500 mg/dL) - prevention of acute pancreatitis ✦ Mixed dyslipidemia, especially with low HDL-C ✦ Type III hyperlipoproteinemia (dysbetalipoproteinemia) ✦ Adjunct in diabetic dyslipidemia (high TG, low HDL pattern) Adverse Effects ✦ GI disturbances - nausea, dyspepsia ✦ Cholelithiasis (increased biliary cholesterol saturation) ✦ Myopathy - risk increases markedly when combined with statins ✦ Hepatotoxicity; mild rise in serum creatinine
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  CLASS 3 ·RESINS Bile Acid Sequestrants - Mechanism of Action Resin (large, non-absorbable cationic polymer) is taken orally and stays in the intestinal lumen It binds negatively-charged bile acids, forming an insoluble complex The bile-acid-resin complex is excreted in feces - enterohepatic circulation of bile acids is interrupted Less bile acid returns to the liver via the portal circulation Liver upregulates 7α-hydroxylase and converts more cholesterol into new bile acids, depleting hepatic cholesterol Hepatocyte responds by increasing LDL-receptor expression → ↑ LDL uptake from plasma → ↓ plasma LDL-C WHY THIS WORKS Since bile acids are synthesized from cholesterol, interrupting their recycling forces continuous hepatic conversion of cholesterol to bile acids. The resulting fall in intracellular cholesterol indirectly upregulates LDL receptors - the same end pathway as statins, but achieved from the intestinal lumen rather than by blocking synthesis. This is why resins pair well with statins. Example: Cholestyramine, Colesevelam
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  Bile Acid Sequestrants- Uses & Adverse Effects Examples: Cholestyramine, Colestipol, Colesevelam Therapeutic Uses ✦ Adjunct to statins for additional LDL-C lowering ✦ Monotherapy in patients who cannot tolerate statins (including children) ✦ Considered safe in pregnancy (not systemically absorbed) ✦ Pruritus associated with cholestasis (bile-acid binding relieves itching) Adverse Effects ✦ Bloating, constipation, abdominal discomfort (most common) ✦ Decreased absorption of fat-soluble vitamins (A, D, E, K) ✦ May raise plasma triglycerides - caution in hypertriglyceridemia ✦ Reduced absorption of many co-administered drugs (give 1 hr before/4 hr after)
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  CLASS 4 ·NIACIN Nicotinic Acid (Niacin) - Mechanism of Action Niacin binds GPR109A receptor on adipocytes Inhibits hormone-sensitive lipase, reducing lipolysis of stored triglycerides Less free fatty acid is released into the circulation and delivered to the liver Reduced FFA substrate lowers hepatic triglyceride synthesis and VLDL assembly/secretion Since VLDL is the metabolic precursor of LDL, less VLDL output means less LDL is ultimately formed Niacin also reduces hepatic uptake/catabolism of Apo A-I, raising HDL-C – its most distinctive effect WHY THIS WORKS Niacin is the only major agent that substantially raises HDL-cholesterol. Its dual action - reduced FFA-driven VLDL/LDL production plus reduced HDL (Apo A-I) catabolism - explains its historically broad effect on the entire lipid panel, although GPR109A-mediated cutaneous flushing is also mechanistically explained by prostaglandin D2 release from Langerhans cells. Example: Niacin (immediate & extended-release)
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  Nicotinic Acid (Niacin)- Uses & Adverse Effects Examples: Nicotinic Acid, Extended-Release Niacin Therapeutic Uses ✦ Mixed dyslipidemia with low HDL-C ✦ Adjunct to statins/fibrates when HDL remains low ✦ Hypertriglyceridemia not controlled by first-line agents ✦ Historically used for secondary CV prevention (less favoured now) Adverse Effects ✦ Cutaneous flushing and pruritus (prevent with aspirin pre-treatment) ✦ Hyperglycemia - caution in diabetes ✦ Hyperuricemia - may precipitate gout ✦ Hepatotoxicity at high doses; GI upset
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  CLASS 5 ·ABSORPTION INHIBITOR Cholesterol Absorption Inhibitor - Mechanism of Action Ezetimibe localizes at the brush border of small-intestine enterocytes Selectively inhibits the NPC1L1 (Niemann-Pick C1-Like 1) sterol transporter Intestinal absorption of dietary and biliary cholesterol is markedly reduced Less cholesterol is packaged into chylomicrons and delivered to the liver Hepatic cholesterol stores fall → SREBP-2 activation → increased LDL- receptor expression Increased hepatic LDL uptake → ↓ Plasma LDL-C (complements statins via a different, non-overlapping site) WHY THIS WORKS Because ezetimibe blocks cholesterol absorption at the intestine while statins block synthesis in the liver, the two mechanisms are complementary rather than redundant. Combination therapy produces additive LDL-C lowering without a proportional increase in statin-related myopathy risk - the rationale for statin/ezetimibe combination tablets. Example: Ezetimibe (often + statin)
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  Cholesterol Absorption Inhibitor(Ezetimibe) - Uses & Adverse Effects Examples: Ezetimibe (alone or fixed-dose with a statin) Therapeutic Uses ✦ Add-on therapy when LDL-C goal is not met on maximal statin dose ✦ Monotherapy in patients who are statin-intolerant ✦ Homozygous familial hypercholesterolemia (adjunct) ✦ Homozygous sitosterolemia (phytosterolemia) Adverse Effects ✦ Generally well tolerated ✦ Diarrhea, ✦ Abdominal pain ✦ Myopathy risk when combined with a statin ✦ Mild elevation of liver transaminases
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  CLASS 6 ·BIOLOGICS PCSK9 Inhibitors - Mechanism of Action Normally, PCSK9 protein binds hepatic LDL receptors on the cell surface The PCSK9-LDL receptor complex is internalized and routed to lysosomes for degradation Monoclonal antibody (or siRNA) binds and neutralizes circulating PCSK9 PCSK9 can no longer bind the LDL receptor - receptor degradation is prevented LDL receptors recycle back to the hepatocyte surface instead of being destroyed More surface LDL receptors are available → markedly increased hepatic LDL-C clearance (up to ~60% reduction) WHY THIS WORKS PCSK9 acts as a natural molecular “brake” on LDL-receptor recycling. Removing that brake maximizes the number of functional receptors on the hepatocyte surface, producing the largest LDL-C reduction of any available class - which is why these agents are reserved for familial hypercholesterolemia and statin-refractory very-high-risk patients. Example: Evolocumab, Alirocumab
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  PCSK9 Inhibitors -Uses & Adverse Effects Examples: Evolocumab, Alirocumab (monoclonal antibodies); Inclisiran (siRNA, less frequent dosing) Therapeutic Uses ✦ Heterozygous and homozygous familial hypercholesterolemia ✦ Statin-intolerant patients needing further LDL-C lowering ✦ Very-high-risk ASCVD not at LDL-C goal despite maximally-tolerated statin + ezetimibe Adverse Effects ✦ Injection-site reactions (erythema, pain) ✦ Nasopharyngitis, influenza-like symptoms ✦ Myalgia ✦ Rare: neurocognitive effects (reported, not firmly established)
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  SYNTHESIS Comparing the SixDrug Classes Class LDL-C Triglycerides HDL-C Primary Site / Target Statins ↓↓↓ ↓ ↑ Liver - HMG-CoA reductase Fibrates ↓ / ↔ ↓↓↓ ↑↑ Liver/Muscle - PPAR-alpha Bile Acid Sequestrants ↓↓ ↑ (may worsen) ↔ Intestine - Bile acid binding Niacin ↓↓ ↓↓ ↑↑↑ Adipose tissue - GPR109A Ezetimibe ↓↓ ↔ ↔ Intestine - NPC1L1 transporter PCSK9 Inhibitors ↓↓↓↓ ↓ ↑ Liver - PCSK9 protein ↓ mild decrease ↓↓ moderate ↓↓↓ marked ↑ mild increase ↑↑ moderate increase ↔ little/no change
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  CLINICAL APPLICATION Choosing theRight Drug Isolated ↑ LDL-C Statin first-line; add ezetimibe, then a PCSK9 inhibitor if goal not reached. Isolated ↑↑ Triglycerides (>500 mg/dL) Fibrate first-line to prevent acute pancreatitis; add omega-3 fatty acids. Low HDL-C predominant Lifestyle change + niacin or fibrate; statins provide only a mild HDL benefit. Mixed Dyslipidemia Statin + fibrate (caution: myopathy risk) or statin + ezetimibe combination. Familial Hypercholesterolemia High-intensity statin + ezetimibe; PCSK9 inhibitor if LDL- C remains uncontrolled. Statin-Intolerant Patient Ezetimibe, bile acid sequestrant, or bempedoic acid; PCSK9 inhibitor for high risk.
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  SUMMARY Summary of KeyPoints ✦ Hyperlipidemia is elevated plasma cholesterol and/or triglycerides - a major modifiable driver of atherosclerosis and cardiovascular disease ✦ Six major drug classes lower lipids through distinct mechanisms: statins (synthesis), fibrates (PPAR-alpha/LPL), resins (bile-acid binding), niacin (adipose lipolysis/HDL), ezetimibe (absorption), and PCSK9 inhibitors (receptor recycling) ✦ Most classes converge on a common final pathway - increasing hepatic LDL-receptor expression - which is why combination therapy is often additive ✦ Statins remain first-line for LDL-lowering; fibrates are preferred for severe hypertriglyceridemia; PCSK9 inhibitors offer the greatest LDL reduction for refractory or familial cases ✦ Drug choice should always be paired with therapeutic lifestyle changes and guided by the patient's specific lipid abnormality and cardiovascular risk