Introduction
Hypertension means persistently high blood pressure due to a rise in systolic or diastolic pressure. It is one of the most common chronic conditions in adults. Most cases are essential hypertension where the exact cause is unknown. A smaller percentage are due to diseases such as chronic kidney disease, endocrine disorders, sleep apnea or certain drugs. Treatment mainly involves lifestyle changes and antihypertensive medicines that lower blood pressure and prevent complications like stroke, heart failure and kidney failure.
Major Classes of Antihypertensive Drugs
- ACE inhibitors
- Angiotensin II receptor blockers (ARBs)
- Diuretics
- Calcium channel blockers (CCBs)
- Beta blockers
- Alpha blockers
- Alpha-2 agonists
- Renin inhibitors
- Direct vasodilators
1. ACE Inhibitors
Examples: Ramipril, Lisinopril, Perindopril
ACE inhibitors block conversion of angiotensin I to angiotensin II, a powerful vasoconstrictor. This causes blood vessels to relax and reduces aldosterone levels, thereby lowering blood pressure and decreasing heart workload.
Side Effects
- Dry cough (common)
- First-dose hypotension
- Hyperkalemia
- Dizziness, fatigue
2. Angiotensin II Receptor Blockers (ARBs)
Examples: Losartan, Telmisartan, Irbesartan, Candesartan
ARBs block angiotensin II receptors, preventing vasoconstriction and reducing blood pressure. They are often used when ACE inhibitors cause persistent cough.
Side Effects
- Hypotension
- Hyperkalemia
- Renal impairment (similar to ACE inhibitors)
3. Diuretics
These drugs increase removal of sodium and water from the body, lowering blood volume and blood pressure.
Types
- Loop diuretics: Furosemide, Bumetanide
- Thiazides: Hydrochlorothiazide, Indapamide
- Potassium-sparing: Amiloride, Spironolactone
Common Side Effects
- Hypovolemia
- Hypokalemia (loop, thiazides)
- Hyperkalemia (spironolactone, amiloride)
- Metabolic alkalosis
4. Calcium Channel Blockers (CCBs)
Examples: Amlodipine, Nifedipine, Verapamil, Diltiazem
CCBs reduce entry of calcium into heart and smooth muscle cells. Dihydropyridines like amlodipine mainly cause vasodilation, while non-dihydropyridines like verapamil also reduce heart rate.
Side Effects
- Ankle swelling
- Flushing
- Headache
- Palpitations
5. Beta Blockers
Examples: Metoprolol, Bisoprolol, Labetalol, Nebivolol
They reduce heart rate, cardiac output and renin release from kidneys. They are especially useful in patients with heart disease, arrhythmias or post-heart attack.
Side Effects
- Fatigue
- Cold extremities
- Nausea
- Headache
6. Alpha Blockers
Examples: Doxazosin, Tamsulosin, Alfuzosin
These drugs block alpha-1 receptors in blood vessels, causing vasodilation and lowering blood pressure. They are usually used when other medicines are not effective.
Side Effects
- Postural hypotension
- Dizziness
- Fainting (especially after first dose)
7. Alpha-2 Agonists
Examples: Clonidine, Methyldopa, Moxonidine
These medicines act on the brain to reduce sympathetic activity, leading to lower blood pressure. Methyldopa is commonly used in pregnancy.
Side Effects
- Dry mouth
- Fatigue
- Sedation
- Rebound hypertension if stopped suddenly
8. Renin Inhibitors
Example: Aliskiren
These drugs block renin release from the kidneys, preventing the formation of angiotensin I and II. They are effective but rarely used due to safety concerns.
Side Effects
- Hyperkalemia
- Hypotension
- Angioedema
- Diarrhoea
9. Direct Vasodilators
Examples: Hydralazine, Sodium Nitroprusside
Hydralazine
Used in hypertension and pregnancy-induced hypertension. It relaxes arteriolar smooth muscle.
Side Effects:
- Tachycardia
- Headache
- Flushing
- Joint pain (rare)
Sodium Nitroprusside
Used in hypertensive emergencies due to very rapid onset. Releases nitric oxide and produces powerful vasodilation.
Side Effects:
- Severe hypotension
- Cyanide toxicity (with prolonged use)
- Arrhythmias
Detailed Notes:
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