Antihypertensive agents are medicines used to lower high blood pressure (hypertension). Hypertension is a chronic condition in which the blood pressure in the arteries remains high, increasing the risk of heart disease, stroke, and kidney damage. These drugs help relax blood vessels, reduce heart workload, or decrease fluid volume to control blood pressure.
What Is Hypertension?
Hypertension is usually defined as:
- Systolic BP ≥ 140 mmHg
- Diastolic BP ≥ 90 mmHg
Common causes include genetics, stress, obesity, high salt intake, lack of exercise, and underlying diseases like kidney disorders.
Goals of Antihypertensive Therapy
- Lower and maintain blood pressure within normal range
- Prevent damage to organs like the heart, brain, and kidneys
- Reduce long-term risks such as stroke and heart failure
Classification of Antihypertensive Agents
1. Diuretics
- Thiazides: Hydrochlorothiazide, Chlorthalidone
- Loop diuretics: Furosemide
- Potassium-sparing: Spironolactone
Mechanism: Increase urine output and reduce body fluid volume, lowering blood pressure.
2. Beta Blockers
- Propranolol
- Atenolol
- Metoprolol
Mechanism: Block beta receptors in the heart, reducing heart rate and cardiac output.
3. ACE Inhibitors
- Captopril
- Enalapril
- Lisinopril
Mechanism: Inhibit conversion of angiotensin I to angiotensin II, a strong vasoconstrictor.
4. Angiotensin II Receptor Blockers (ARBs)
- Losartan
- Valsartan
- Telmisartan
Mechanism: Block angiotensin II receptors, causing blood vessel relaxation.
5. Calcium Channel Blockers
- Amlodipine
- Verapamil
- Diltiazem
Mechanism: Prevent calcium entry into smooth muscle cells, reducing vascular resistance.
6. Alpha Blockers
- Prazosin
- Doxazosin
Mechanism: Block alpha-1 receptors, causing vasodilation.
7. Centrally Acting Agents
- Clonidine
- Methyldopa
Mechanism: Reduce sympathetic nerve signals that increase blood pressure.
8. Vasodilators
- Hydralazine
- Minoxidil
- Sodium nitroprusside (emergency use)
Mechanism: Directly relax blood vessels.
Major Drug Profiles
Hydrochlorothiazide
Class: Thiazide diuretic.
Mechanism: Reduces sodium and water reabsorption.
Uses: First-line treatment for primary hypertension.
Propranolol
Class: Beta blocker.
Uses: Hypertension, tremors, migraine prevention.
Caution: Avoid in asthma patients due to bronchoconstriction.
Captopril
Class: ACE inhibitor.
Uses: Hypertension, diabetic kidney disease.
Side effects: Dry cough, hyperkalemia.
Losartan
Class: ARB.
Mechanism: Blocks angiotensin II effects.
Advantage: No dry cough (unlike ACE inhibitors).
Amlodipine
Class: Calcium channel blocker.
Uses: Hypertension, angina.
Side effects: Ankle swelling, headache.
Hydralazine
Class: Vasodilator.
Use: Severe hypertension and hypertensive emergencies.
Methyldopa
Class: Centrally acting agent.
Use: Safe antihypertensive for pregnancy.
General Side Effects of Antihypertensive Drugs
- Dizziness or light-headedness
- Fatigue
- Headache
- Electrolyte imbalance (with diuretics)
- Bradycardia (with beta blockers)
Detailed Notes:
For PDF style full-color notes, open the complete study material below:
