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Classification of Cardiovascular Drugs
Cardiovascular drugs are grouped by their primary therapeutic use and mechanism of action. The major classes are outlined below.
1. Antihypertensive Drugs
These are the largest and most clinically used group. They are sub-classified by mechanism:
| Subclass | Mechanism | Examples |
|---|---|---|
| Thiazide diuretics | Inhibit NaCl reabsorption in distal tubule | Hydrochlorothiazide, Chlorthalidone |
| Loop diuretics | Block Na-K-2Cl cotransporter in loop of Henle | Furosemide, Bumetanide |
| Potassium-sparing diuretics | Antagonize aldosterone or block ENaC | Spironolactone, Amiloride |
| ACE inhibitors (ACEi) | Block angiotensin-converting enzyme | Enalapril, Lisinopril, Captopril |
| Angiotensin receptor blockers (ARBs) | Block AT1 receptor | Losartan, Valsartan |
| Beta-blockers (β-blockers) | Block β-adrenergic receptors | Metoprolol, Atenolol, Carvedilol |
| Calcium channel blockers (CCBs) | Block L-type Ca²⁺ channels | Amlodipine, Nifedipine, Verapamil, Diltiazem |
| Alpha-1 blockers | Block α1 receptors on vascular smooth muscle | Prazosin, Doxazosin |
| Central alpha-2 agonists | Reduce sympathetic outflow centrally | Clonidine, Methyldopa |
| Direct vasodilators | Directly relax vascular smooth muscle | Hydralazine, Minoxidil |
| Neprilysin inhibitors (ARNi) | Block angiotensin + neprilysin | Sacubitril/Valsartan |
From Katzung's Basic and Clinical Pharmacology, 16th Edition and Goodman & Gilman's Pharmacological Basis of Therapeutics
2. Antiarrhythmic Drugs (Vaughan-Williams Classification)
The Vaughan-Williams scheme classifies antiarrhythmic drugs (AADs) by their predominant effect on the cardiac action potential. Note that many agents have overlapping actions across classes - this is an important limitation of the classification.
| Class | Mechanism | Examples | Key Adverse Effects |
|---|---|---|---|
| IA | Na⁺ channel block (intermediate kinetics) - slows Phase 0, prolongs repolarization | Quinidine, Procainamide, Disopyramide | QT prolongation, torsades de pointes, lupus-like syndrome (procainamide), cinchonism (quinidine) |
| IB | Na⁺ channel block (rapid kinetics) - shortens Phase 3 repolarization | Lidocaine, Mexiletine | Seizures, CNS toxicity, tremor, ataxia |
| IC | Na⁺ channel block (slow kinetics, high potency) - markedly slows Phase 0 | Flecainide, Propafenone | Bradycardia, proarrhythmia, bronchospasm (propafenone) |
| II | β-adrenergic receptor blockade - inhibits Phase 4 spontaneous depolarization | Metoprolol, Atenolol, Esmolol | Bradycardia, heart block, bronchospasm, fatigue |
| III | K⁺ channel block - prolongs action potential duration and refractory period | Amiodarone, Sotalol, Dofetilide, Ibutilide | QT prolongation, torsades; amiodarone: multiorgan toxicity (pulmonary, thyroid, hepatic) |
| IV | Ca²⁺ channel block (non-dihydropyridines) - slows SA/AV nodal conduction | Verapamil, Diltiazem | Bradycardia, AV block, constipation |
| Others | Multiple/miscellaneous mechanisms | Adenosine, Digoxin, Ranolazine | Adenosine: transient asystole; Digoxin: arrhythmias, GI toxicity |
Note: Amiodarone has actions across all four classes (I, II, III, IV), which makes it uniquely effective but also uniquely toxic. - Harrison's Principles of Internal Medicine, 22nd Edition
3. Drugs for Heart Failure
| Drug Class | Examples | Mechanism |
|---|---|---|
| ACE inhibitors / ARBs / ARNi | Lisinopril, Valsartan, Sacubitril-Valsartan | Reduce preload and afterload, reverse remodeling |
| Beta-blockers | Carvedilol, Metoprolol succinate, Bisoprolol | Reduce sympathetic stimulation, reverse remodeling |
| Diuretics | Furosemide, Spironolactone | Reduce volume overload |
| SGLT2 inhibitors | Empagliflozin, Dapagliflozin | Natriuresis, anti-fibrotic, metabolic benefits |
| Cardiac glycosides (positive inotropes) | Digoxin | Inhibit Na⁺/K⁺-ATPase → increased intracellular Ca²⁺ → stronger contraction; also slows AV conduction |
| Other inotropes | Dobutamine, Milrinone, Levosimendan | Used in acute decompensated heart failure |
| Hydralazine + Nitrates | Hydralazine + Isosorbide dinitrate | Alternative vasodilator combo (especially in African Americans) |
Katzung's Basic and Clinical Pharmacology, 16th Edition
4. Antianginal Drugs
| Class | Examples | Mechanism |
|---|---|---|
| Nitrates | Nitroglycerin, Isosorbide mononitrate | Donate NO → venodilation → reduce preload; also dilate coronary arteries |
| Beta-blockers | Metoprolol, Atenolol | Reduce heart rate and oxygen demand |
| Calcium channel blockers | Amlodipine, Verapamil, Diltiazem | Reduce coronary vasospasm, reduce afterload |
| Ranolazine | Ranolazine | Blocks late Na⁺ current → reduces intracellular Ca²⁺ overload |
5. Lipid-Lowering Drugs (Antidyslipidemics)
| Class | Examples | Mechanism |
|---|---|---|
| Statins (HMG-CoA reductase inhibitors) | Atorvastatin, Rosuvastatin, Simvastatin | Reduce hepatic cholesterol synthesis → upregulate LDL receptors |
| Ezetimibe | Ezetimibe | Blocks intestinal cholesterol absorption (NPC1L1 inhibitor) |
| PCSK9 inhibitors | Alirocumab, Evolocumab | Prevent LDL receptor degradation → increase LDL clearance |
| Fibrates | Fenofibrate, Gemfibrozil | Activate PPARα → reduce triglycerides, increase HDL |
| Bile acid sequestrants | Cholestyramine, Colesevelam | Bind bile acids → force hepatic use of cholesterol to make new bile |
| Nicotinic acid (Niacin) | Niacin | Reduces VLDL synthesis; raises HDL (less used now due to side effect profile) |
6. Anticoagulant / Antiplatelet / Thrombolytic Drugs
| Class | Examples | Mechanism |
|---|---|---|
| Antiplatelets | Aspirin, Clopidogrel, Ticagrelor, Abciximab | Block platelet aggregation via COX-1, ADP receptors (P2Y12), or GP IIb/IIIa |
| Heparins | Unfractionated heparin, Enoxaparin | Activate antithrombin III → inhibit thrombin and Factor Xa |
| Vitamin K antagonists | Warfarin | Inhibit factors II, VII, IX, X (vitamin K-dependent) |
| Direct oral anticoagulants (DOACs) | Rivaroxaban, Apixaban (anti-Xa); Dabigatran (anti-IIa) | Direct inhibition of specific clotting factors |
| Thrombolytics | Alteplase (tPA), Streptokinase | Convert plasminogen to plasmin → lyse clots |
Summary Overview
CARDIOVASCULAR DRUGS
├── 1. Antihypertensives (diuretics, ACEi, ARBs, CCBs, beta-blockers, vasodilators)
├── 2. Antiarrhythmics (Vaughan-Williams Class I-IV + others)
├── 3. Heart Failure drugs (ACEi/ARB/ARNi, beta-blockers, diuretics, SGLT2i, inotropes)
├── 4. Antianginals (nitrates, beta-blockers, CCBs, ranolazine)
├── 5. Lipid-lowering agents (statins, PCSK9i, fibrates, ezetimibe)
└── 6. Antithrombotic agents (antiplatelets, anticoagulants, thrombolytics)
Sources: Lippincott Illustrated Reviews: Pharmacology | Harrison's Principles of Internal Medicine, 22nd Ed. | Katzung's Basic and Clinical Pharmacology, 16th Ed. | Goodman & Gilman's Pharmacological Basis of Therapeutics
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