Beta Blockers: Classification, Actions, Side Effects, and Clinical Uses

Beta Blockers: Classification, Actions, Side Effects, and Clinical Uses

Question. Write a short answer on beta blockers.

Answer. These drugs inhibit responses mediated by the adrenergic β blockers.

Classification Beta Blockers.

1. Cardioselective (β1): Metoprolol, atenolol, acebutolol.
2. β2 selective: Butoxamine.
3. Nonselective (β1+ β2): Propranolol, nadolol, sotalol, timolol.

Actions Beta Blockers

1. Heart: These drugs decrease the force of contraction, decreases AV conduction, decreases heart rate, decreases automaticity of myocardial fiers, thus cardiac output is decreased.
2. Blood vessels: On prolong administration BP falls in hypertensives.
3. Respiratory system: It causes increase of bronchoconstriction in asthmatics.
4. Eye: β-blockers decrease aqueous humor secretion.

Adverse Reactions Beta Blockers

1. CVS: Bradycardia, heart block and can precipitate heart failure.
2. Respiratory system: These drugs can precipitate bronchial asthma.
3. CNS: Disturbed sleep, fatigue, hallucinations and mental depression.
4. Muscular weakness and tiredness
5. Abrupt withdrawal can cause angina or frank myocardial infarction.

Contraindications Beta Blockers

1. They are contraindicated in asthmatics and COPD.
2. They are contraindicated in patients of Prinzmetal angina.
3. They are contraindicated in peripheral vascular disease.
4. They are contraindicated in patients with low cardiac reserve.
5. They are contraindicated in diabetic who are taking oral anti­diabetic drugs as they delay recovery from hypoglycemia.

Uses or Indications of β Blockers

1. Hypertension: β blockers are used to treat all the grades of hypertension.
   They are also indicated in angina, myocardial infarction and cardiac arrhythmias.
2. In prophylaxis of angina and myocardial infarction: β blockers decreases oxygen demand of myocardium and decreases the heart rate.
   These drugs reduces the frequency of angina attcks.
   They are indicated in acute phase of myocardial infarction so that they limit the size of infarct.
3. In cardiac arrhythmias: They are indicated in atrial arrhythmias i.e. atrial fibrillation, atrial flutter and paroxysmal supraventricular tachycardia.
4. Congestive cardiac failure: Chronic usage of β blockers reducec rate of mortality during chronic heart failure.
5. Pheochromocytoma: These drugs control cardiac manifestations produced by pheochromocytoma.
6. Glaucoma: They decrease intra­ocular pressure by decreasing secretion of aqueous humor. Timolol is the choice of drug.
7. In prophylaxis of migraine: They decreases the frequency of migraine headache.
8. Hyperthyroidism: Sign and symptoms of hyperthyroidism decreases due to blockade of β receptors.
9. Essential tremors: Propranolol provides relief in tremors.
10. Anxiety: It acts as anti­anxiety drug.
11. Alcohol withdrawl: Propranolol provides benefi in alcohol withdrawl.
12. Dissecting aortic aneurysm: β blockers reduce cardiac contractility as well as development of pressure during systole.

Question.64. Write short answer on calcium channel blocker.

Answer. Following are the calcium channel blockers: