DRUGS ACTING ON THE CARDIOVASCULAR SYSTEM: A TEACHER’S COMPREHENSIVE GUIDE
Welcome, future pharmacologists and healthcare professionals!
The cardiovascular system is one of the most vital systems in the human body, and drugs acting on it are among the most commonly prescribed medications worldwide. From hypertension and angina to heart failure and arrhythmias, cardiovascular diseases remain the leading cause of death globally. As a pharmacology educator with years of experience teaching cardiovascular pharmacology, I have observed that students often find this topic challenging due to the numerous drug classes and their complex mechanisms. Let me tell you: Understanding cardiovascular drugs is essential for every healthcare professional.
In this comprehensive guide, I will walk you through the major classes of cardiovascular drugs—antihypertensives, anti-anginal drugs, anti-arrhythmic drugs, drugs used in atherosclerosis, drugs used in congestive heart failure, and drug therapy for shock. By the end of this article, you will have a thorough understanding of these essential pharmacological agents. Let us begin!
Dpharmguru’s exam insights:
Cardiovascular drugs are frequently tested in pharmacology exams. Remember: Hypertension is increased systemic arterial pressure. Anti-hypertensives include ACE inhibitors, ARBs, CCBs, beta-blockers, diuretics, and vasodilators. Anti-anginal drugs include nitrates, CCBs, and beta-blockers. Anti-arrhythmics are classified into four classes based on their mechanism. Statins are used in atherosclerosis. Digoxin is used in CHF. These are classic exam questions!
ANTI-HYPERTENSIVE DRUGS
Hypertension is a condition in which the blood pressure of the systemic artery increases beyond the normal pressure. The drugs used in the treatment of hypertension are known as anti-hypertensive drugs.
Classification of Anti-hypertensive Drugs
- ACE Inhibitors: Captopril, Enalapril, Lisinopril, Ramipril, Perindopril, Fosinopril, Trandolapril, Quinapril, Benazepril
- Angiotensin II Receptor Antagonists: Losartan, Candesartan, Valsartan, Eprosartan, Irbesartan
- Ganglion Blockers: Trimethaphan
- Adrenergic Drugs:
- Centrally Acting: Clonidine, Methyldopa, Guanabenz, Guanfacine
- Adrenergic Neuron Blockers: Guanethidine, Reserpine
- Sympatholytics: α-Blockers (Prazosin, Terazosin, Doxazosin, Phenoxybenzamine, Phentolamine), β-Blockers (Propranolol, Atenolol, Esmolol, Metoprolol), α & β Blockers (Labetalol, Carvedilol)
- Ca²⁺ Channel Blockers: Verapamil, Nifedipine, Nicardipine, Nimodipine, Amlodipine, Felodipine
- Vasodilators:
- Arteriolar Dilators: Hydralazine, Minoxidil, Diazoxide
- Arteriolar and Venular Dilators: Sodium nitroprusside
- Diuretics:
- Thiazides: Hydrochlorothiazide, Chlorthalidone, Indapamide
- Loop Diuretics: Furosemide, Bumetanide, Torsemide
- K⁺ Sparing Diuretics: Spironolactone, Amiloride, Triamterene
ACE Inhibitors
Pharmacological Actions: Cause vasodilation, lower systemic arterial resistance, SBP and DBP. Increase renal, cerebral, and coronary blood flow. Reduce aldosterone secretion.
Indications: Hypertension (first-line drugs), Congestive Heart Failure (CHF), Myocardial Infarction (MI), Diabetic Nephropathy, Scleroderma Crisis.
Contraindications: Severe bilateral renal artery stenosis, aortic stenosis, coarctation of aorta, pregnancy.
Adverse Effects: Dizziness, angioedema, loss of taste, photosensitivity, severe hypotension, dry cough, hyperkalaemia, blood dyscrasias, renal impairment.
Angiotensin II Receptor Antagonists (ARBs)
Pharmacological Actions: Block AT₁ receptors found in the heart, blood vessels, and kidneys. Reduce the action of angiotensin II—a hormone that constricts blood vessels and increases blood pressure.
Indications: Hypertension when patient is intolerant to ACE inhibitors; heart failure; diabetic nephropathy.
Adverse Effects: Angioedema (less common than ACE inhibitors), hyperkalaemia, oliguria, progressive azotaemia.
Centrally Acting Sympatholytic Drugs
Methyldopa: Alpha-2 adrenergic agonist; relaxes blood vessels; used in hypertension. Contraindicated in active hepatic disease. Adverse effects: nasal stuffiness, headache, sedation, mental depression, dryness of mouth, bradycardia, gynaecomastia.
Clonidine: Centrally acting α₂-adrenergic agonist; crosses BBB and acts on hypothalamus to decrease blood pressure. Uses: opioid/alcohol withdrawal, pre-anaesthetic agent, migraine prophylaxis. Adverse effects: dry mouth and eyes, sedation, depression, bradycardia, impotence.
Adrenergic Neuron Blockers
Reserpine: Alkaloid from Rauwolfia serpentina; slow-acting; complete effect within 2-3 weeks. Not used clinically due to serious adverse effects (nasal congestion, lethargy, depression, diarrhoea, impotence).
Guanethidine: Inhibits transmission in post-ganglionic adrenergic nerves; prevents norepinephrine release. Used in moderate and severe hypertension. Adverse effects: orthostatic hypotension, sexual dysfunction, diarrhoea.
α-Blockers
Examples: Prazosin, Terazosin, Doxazosin, Phenoxybenzamine, Phentolamine
Pharmacological Actions: Lower blood pressure by preventing norepinephrine from tightening muscles in walls of small arteries and veins.
Indications: High blood pressure, enlarged prostate, Raynaud’s disease, scleroderma, pheochromocytoma.
Adverse Effects: Dizziness, drowsiness, headache, lethargy, palpitations, nausea.
β-Blockers
Examples: Propranolol, Atenolol, Metoprolol
Pharmacological Actions: Negative inotropic and chronotropic action on heart; increase airway resistance; reduce RAAS activity; decrease sympathetic activity.
Contraindications: Peripheral vascular diseases, diabetes mellitus, COPD, asthma.
Adverse Effects: Fatigue, bradycardia, decreased exercise tolerance, masking of hypoglycaemia symptoms, increased serum triglycerides, lowered HDL cholesterol.
Calcium Channel Blockers (CCBs)
Examples: Verapamil, Nifedipine, Amlodipine, Diltiazem
Pharmacological Action: Stop calcium from entering cells of the heart and arteries; allow blood vessels to relax and open; some slow down heart rate.
Indications: Angina pectoris, hypertension, arrhythmias (PSVT), hypertrophic cardiomyopathy.
Adverse Effects: Dizziness, headache, peripheral oedema, flushing, tachycardia, rash, gingival hyperplasia.
Vasodilators
Hydralazine: Lowers BP by directly relaxing arteriolar wall. Onset slow but duration prolonged.
Sodium Nitroprusside: Drug of choice in hypertensive emergencies.
Adverse Effects: Tachycardia, angina, headache, dizziness, fluid retention, nasal congestion, hepatitis.
Diuretics
Thiazides: Hydrochlorothiazide, Chlorthalidone—inexpensive first-line antihypertensives.
Loop Diuretics: Furosemide, Bumetanide—used in hypertensive patients with chronic renal failure or CHF.
Potassium-sparing Diuretics: Spironolactone, Amiloride—correct potassium loss caused by thiazides and loop diuretics.
Adverse Effects: Hypercalcaemia, hypokalaemia, hypernatraemia, hypomagnesaemia, hyperglycaemia, hyperlipidaemia, hyperuricaemia.
ANTI-ANGINAL DRUGS
Angina pectoris (chest pain) is a symptom experienced due to myocardial ischaemia. Anti-anginal drugs aim at restoring the balance between the supply and demand of oxygen in the ischaemic area of the myocardium.
Classification
- Vasodilator Drugs:
- Organic Nitrites and Nitrates: Isosorbide dinitrate, Isosorbide mononitrate, Nitro-glycerine
- Calcium Channel Blockers: Amlodipine, Nifedipine, Diltiazem, Verapamil
- Potassium Channel Opener: Nicorandil
- β-Adrenoceptor Antagonists: Atenolol, Metoprolol, Nadolol, Propranolol
- Metabolic Modifiers: Ranolazine, Trimetazidine
Organic Nitrates and Nitrites
Pharmacological Actions: Relax systemic venous and arteriolar bed; reduce preload and afterload; increase exercise tolerance.