Hypertension is a chronic condition characterized by elevated blood pressure, increasing the risk of heart disease, stroke, and kidney disease.
Anti-hypertensive drugs aim to lower blood pressure through various mechanisms.
Major Classes of Anti-Hypertensive Drugs:
1) Diuretics
Thiazide Diuretics
Examples: Hydrochlorothiazide, Chlorthalidone
MOA: Inhibit Na⁺/Cl⁻ reabsorption in the distal convoluted tubule.
Benefits: Reduce blood volume and peripheral resistance.
Side Effects: Hypokalemia, hyponatremia, hypercalcemia.
Loop Diuretics
Examples: Furosemide
MOA: Inhibit Na⁺/K⁺/2Cl⁻ cotransporter in the ascending loop of Henle.
Benefits: Potent diuresis, useful in edema.
Side Effects: Hypokalemia, ototoxicity.
Potassium-Sparing Diuretics
Examples: Spironolactone, Triamterene
MOA: Inhibit sodium channels or aldosterone receptors in the collecting ducts.
Benefits: Prevent hypokalemia.
Side Effects: Hyperkalemia, gynecomastia (spironolactone).
2) ACE Inhibitors
Examples: Lisinopril, Ramipril
MOA: Block conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone-mediated volume retention.
Benefits: Lower blood pressure, protect renal function in diabetes.
Side Effects: Persistent cough, hyperkalemia, angioedema.
3) Angiotensin II Receptor Blockers (ARBs)
Examples: Losartan, Valsartan
MOA: Block angiotensin II type 1 receptors, preventing vasoconstriction.
Benefits: Similar to ACE inhibitors without causing cough.
Side Effects: Hyperkalemia, dizziness.
4) Calcium Channel Blockers
Dihydropyridines
Examples: Amlodipine
MOA: Predominantly vasodilatory effects by blocking L-type calcium channels in vascular smooth muscle.
Benefits: Lower blood pressure, treat angina.
Side Effects: Peripheral edema, flushing.
Non-Dihydropyridines
Examples: Diltiazem, Verapamil
MOA: Block calcium channels in the heart, reducing heart rate and contractility.
Benefits: Lower blood pressure, control arrhythmias.
Side Effects: Bradycardia, constipation (verapamil).
5) Beta-Blockers
Examples: Metoprolol, Atenolol, Propranolol
MOA: Block β-adrenergic receptors, reducing heart rate and cardiac output.
Benefits: Lower blood pressure, reduce myocardial oxygen demand.
Side Effects: Bradycardia, fatigue, bronchoconstriction (non-selective).
Considerations: Caution in asthma, diabetes.
6) Alpha-Blockers
Examples: Prazosin, Doxazosin
MOA: Block α-adrenergic receptors, causing vasodilation.
Benefits: Lower blood pressure.
Side Effects: Orthostatic hypotension, dizziness.
7) Central Agonists
Examples: Clonidine, Methyldopa
MOA: Activate central α₂-adrenergic receptors, reducing sympathetic outflow.
Benefits: Lower blood pressure effectively.
Side Effects: Sedation, dry mouth, rebound hypertension upon abrupt withdrawal.
8) Renin Inhibitors
Examples: Aliskiren
MOA: Directly inhibit renin, decreasing angiotensin I and II production.
Benefits: Lower blood pressure, alternative for ACE inhibitor/ARB intolerant patients.
Side Effects: Diarrhea, hyperkalemia, renal impairment.
Clinical Considerations:
First-Line Therapy: Often includes ACE inhibitors, ARBs, thiazide diuretics, or calcium channel blockers.
Comorbid Conditions: Drug choice may depend on conditions like diabetes, heart failure, or chronic kidney disease.
Lifestyle Modifications: Essential alongside pharmacotherapy (e.g., diet, exercise, smoking cessation).