Antihypertensive Drugs

Antihypertensive Drugs

Antihypertensive drugs are agents used to reduce the elevated blood pressure. They can be classified based on the mechanism of action as under:

Agents interfering with sympathetic activity

1. Alpha adrenergic receptor blockers: Phentolamine, tolazoline, prazosin,
2. Beta adrenergic blockers: Propranolol, Atenolol, Metoprolol
3. Alpha and Beta adrenergic blocker: Labetalol
4. Agents interfering with central sympathetic activity: Clonidine

Vasodilators as hypertensive drugs

1. Nitrates: Amyl nitrate, isosorbide dinitrate, glyceryl trinitrate ( nitroglycerine) are used as vasodilators.  
2. Calcium channel blockers: Drugs under this category include verapamil, diltiazem, nifedipine, nimodipine and amlodipine.
3. Potassium channel activators: Drugs under this category include cromokalin, pinacidil, minoridil and diazoxide.
4. Agents that act by increasing cyclic nucleotide concentration:  Nitroprusside
5. Vasodilators with unknown mechanism of action: Hydralazine
6. Agents acting through inhibition of Angiotensin
   • Angiotensin Converting enzyme inhibtors: Enalapril, Captopril
   • Angiotensin Receptor blocker: Losartan

Clinical use of Antihypertensive drugs

These drugs category used in clinics, use also described below-

1. Diuretics
2. ACE inhibitors / AT₁ antagonists
3. β -adrenergic blockers
4. Calcium channel blockers

Clinical use of Diuretics as Antihypertensive drugs

• Thiazides and related drugs are drugs of choice in uncomplicated hypertension
• Thiazides are mild antihypertensives
• Effective in elderly patients
  • They are effective in Isolated systolic hypertension,
  • low renin hypertension
  • Obese with volume overload
• They are indicated in hypertension complicated by
  • Heart failure
  • Risk of Coronary artery disease
  • Diabetes
• Diuretics should be avoided in
  • Patients with abnormal lipid profile
  • Pregnancy induced hypertension

Clinical use of ACE Inhibitors/AT1 blockers as Antihypertensive drugs

• First choice drug in all grades of essential as well as renovascular hypertension
• ACE inhibitors should be avoided in
  • Bilateral renal artery stenosis
  • Pregnancy
  • Hyperkalaemia
• Most appropriate antihypertensives in patients with
  • Diabetes
  • Nephropathy/chronic kidney disease
  • Left ventricular hypertrophy
  • Congestive heart failure
  • Post Myocardial Infarction
  • Gout
  • Dyslipidemia
• They appear to be more effective in relatively young patients
• ACE inhibitors produce persistent cough (during the first two weeks) and dysguesia (loss of taste sensation).

Clinical use of β -blockers as Antihypertensive drugs

• Mild antihypertensive
• They are indicated as antihypertensive in patients with
  • Stable heart failure
  • Post myocardial infarction
  • High coronary artery disease risk
• Highly suitable for
  • Patients with coexisting anxiety or tachycardia
  • Relatively young non-obese patients
  • High renin hypertensive patients
  • Migraine patients
  • Pregnant individuals
• Contraindicated in
  • Peripheral vascular disease
  • Pulmonary disease-asthma, COPD
  • Cardiac disease-Conduction defects, decompensated heart failure
  • Abnormal lipid profile

Clinical use of Calcium Channel blockers as Antihypertensive drugs

• Preferred in
  • Elderly hypertensive patients who have poor arterial wall compliance
  • Isolated systolic hypertension
  • Asthma/COPD patients
  • Pregnant hypertensive
  • Diabetes
• Prevents recurrent stroke
• Verapamil and diltiazem should be avoided in
  • Congestive heart failure , cardiac conduction defects
• Dihydropyridines should be avoided in
  • Ischaemic heart disease
  • Post myocardial infarction
  • Gastroesophageal reflux
  • Males with prostate enlargement