Antihypertensive Drugs_ A Comprehensive Review

Antihypertensive Drugs: A Comprehensive Review

Hypertension remains a significant global health concern, contributing to cardiovascular morbidity and mortality. Antihypertensive drugs play a crucial role in managing this condition. This review article provides an overview of the major classes of antihypertensive medications, their mechanisms of action, indications, and recent developments in the field.

Angiotensin-Converting Enzyme (ACE) Inhibitors

Mechanism: Inhibit the conversion of angiotensin I to angiotensin II

Examples: Lisinopril, Ramipril, Enalapril

Indications: Hypertension, heart failure, post-MI, diabetic nephropathy

Side effects: Dry cough, angioedema, hyperkalemia

Angiotensin Receptor Blockers (ARBs)

Mechanism: Block the action of angiotensin II at AT1 receptors

Examples: Losartan, Valsartan, Telmisartan

Indications: Similar to ACE inhibitors, often used as alternatives when ACE inhibitors are not tolerated

Side effects: Generally well-tolerated, potential for hyperkalemia

Calcium Channel Blockers (CCBs)

Mechanism: Block calcium influx into vascular smooth muscle and cardiac cells

Examples: Amlodipine, Nifedipine, Diltiazem, Verapamil

Indications: Hypertension, angina, certain arrhythmias

Side effects: Peripheral edema, constipation (verapamil), gingival hyperplasia

Beta-Blockers

Mechanism: Block beta-adrenergic receptors, reducing heart rate and cardiac output

Examples: Metoprolol, Atenolol, Carvedilol

Indications: Hypertension, post-MI, heart failure, angina

Side effects: Fatigue, bradycardia, bronchospasm (in susceptible individuals)

Thiazide Diuretics

Mechanism: Inhibit sodium-chloride cotransporter in distal convoluted tubule, promoting sodium and water excretion

Examples: Hydrochlorothiazide, Chlorthalidone, Indapamide

Indications: Hypertension, often used as first-line therapy or in combination

Side effects: Electrolyte imbalances, hyperuricemia, glucose intolerance

Loop Diuretics

Mechanism: Inhibit sodium-potassium-chloride cotransporter in the loop of Henle

Examples: Furosemide, Bumetanide, Torsemide

Indications: Hypertension with renal impairment, heart failure

Side effects: Electrolyte imbalances, ototoxicity at high doses

Potassium-Sparing Diuretics

Mechanism: Block sodium channels in collecting duct (amiloride, triamterene) or antagonize aldosterone (spironolactone, eplerenone)

Examples: Spironolactone, Eplerenone, Amiloride

Indications: Hypertension, heart failure, primary aldosteronism

Side effects: Hyperkalemia, gynecomastia (spironolactone)

Alpha-1 Blockers

Mechanism: Block alpha-1 adrenergic receptors, causing vasodilation

Examples: Prazosin, Doxazosin, Terazosin

Indications: Hypertension, benign prostatic hyperplasia

Side effects: Orthostatic hypotension, first-dose syncope

Central-Acting Agents

Mechanism: Stimulate central alpha-2 receptors or imidazoline receptors, reducing sympathetic outflow

Examples: Clonidine, Methyldopa, Moxonidine

Indications: Hypertension, particularly in pregnancy (methyldopa)

Side effects: Dry mouth, sedation, rebound hypertension upon discontinuation

Recent Developments and Emerging Therapies:

Combination Therapies: Fixed-dose combinations of multiple antihypertensive agents have gained popularity, improving adherence and efficacy.

ARNI (Angiotensin Receptor-Neprilysin Inhibitor): Sacubitril/valsartan, initially approved for heart failure, shows promise in resistant hypertension.

Endothelin Receptor Antagonists: Drugs like macitentan are being studied for resistant hypertension, particularly in patients with chronic kidney disease.