Adrenergic Antagonist Question and Answers

Adrenergic Antagonist Important Notes

1. Sympathetic blocking drugs

Adrenergic Antagonist Sympathetic Blocking Drugs

2. Uses of alpha-blockers 

  • Pheochromocytoma
  • Hypertension
  • Peripheral vascular diseases
  • Congestive cardiac failure
  • Benign hypertrophy of the prostate

3. Abrupt withdrawal of beta-blocker after chronic use causes

  • Rebound hypertension
  • Worsening of angina
  • Sudden death

Beta 2 Adrenergic Antagonist

Adrenergic Antagonist Long Essays

Question 1. Classify beta-adrenergic receptor blockers. Describe the pharmacological actions, uses and adverse effects of propranolol.


Beta-adrenergic receptor blockers:

β-blockers are drugs that block the actions of catecholamines mediated through β -receptors.

Beta-Adrenergic Receptor Blockers Classification:

1. Nonselective

  • Without intrinsic sympathomimetic activity
    • Propranolol, sotalol, timolol.
  • With intrinsic sympathomimetic activity
    • Pindolol, oxprenolol
  • With additional blocking property.
    • Labetalol, carvedilol.

Beta 2 Adrenergic Antagonist

2. Cardioselective

  • Metoprolol, atenolol, bisoprolol, esmolol, betaxolol
  • Propranolol-Propranolol is a first-generation non-selective β-blocker with intrinsic sympathomimetic activity.

Pharmacological actions:

1. CVS:

  • Decreases heart rate, force of contraction and cardiac output.
  • Decreases BP.
  • Cardiac work and oxygen consumption are reduced.
  • AV conduction is delayed
  • Blocks cardiac stimulant action of adrenergic drugs.
  • Improves exercise tolerance in angina patients.

Read And Learn More: Pharmacology Question and Answers

2. Blood vessels.

  • Blocks vasodilation produced by isoprenaline.

3. Respiratory tract

  • Blocks β2 receptors in bronchial smooth muscles
  • Increases bronchial resistance.

4. CNS.

Mild central effects like behavioural changes, forgetfulness, increased dreaming and nightmares occur.

5. Local anaesthetic.

  • Potent anaesthetic agent but not used due to irritation.

Beta 2 Adrenergic Antagonist

6. Eye:

  • Reduces intraocular pressure.
  • Decreases secretion of aqueous humour.

7. Metabolic:

  • Blocks adrenergic ally-induced lipolysis.
  • Inhibits glycogenolysis.

8. Sekeletal muscle.

  • Inhibits adrenergic ally-provoked tremors.

B Adrenergic Antagonist

Beta-Adrenergic Receptor Blockers Uses:

  • Hypertension
  • Prophylaxis of exertional angina.
  • Congestive cardiac failure.
  • Dissecting aortic aneurysm.
  • Cardiac arrhythmia.
  • Myocardial infraction.
  • Pheochromocytoma.
  • Prophylaxis of migrane.
  • Glaucoma.
  • Anxiety.
  • Essential tremor.
  • Hypertrophic obstructive cardiomyopathy.

Beta-Adrenergic Receptor Blockers Adverse effects:

  • Hypotension.
  • Impairment of myocardial function.
  • Cold extremities.
  • Precipitate acute asthmatic attacks
  • Fatigue, weakness.
  • Abrupt withdrawal causes rebound hypertension.
  • Impairment of carbohydrate tolerance.

B Adrenergic Antagonist

Adrenergic Antagonist Short Essays

Question 1. Adrenergic alpha-blockers.


Adrenergic alpha-blockers are drugs that block the adrenergic responses mediated through alpha-adrenergic receptors.

Adrenergic alpha-blockers Classification:

1. Non-equilibrium.

  • Phenoxybenzamine.

2. Equilibrium or competitive.

  • Non-selective.
    • Ergot alkaloids – ergotamine, ergotoxine.
    • Hydrogenated ergot alkaloids – dihydro- ergotamine.
    • Imidazolines – tolazoline.
    • Miscellaneous – chlorpromazine
  • α1- selective.
    • Prazosin, Terazosin, Doxazosin.
  • α2 – selective. – yohimbine.

Adrenergic alpha-blockers Actions:

  • Inhibits vasoconstriction, leads to vasodilatation and decreases BP.
  • Enhances release of noradrenaline by α2 blocked
  • Reflex tachycardia.
  • Nasal stiffness and miosis.
  • Increased intestinal motility.
  • Reduced tone of smooth muscle.

Adrenergic alpha-blockers Uses:

  • Pheochromocytoma.
  • Hypertension.
  • Secondary shock.
  • Peripheral vascular diseases.
  • Benign hypertrophy of the prostate.

Adrenergic alpha-blockers Adverse effects:

  • Postural hypotension, palpitation.
  • Nasal stiffness, miosis.
  • Impaired ejaculation.
  • Impotence.

Question 2. Cardioselective beta blockers.


Cardioselective beta blockers Actions:

  • Selectively block β1 receptors.
  • Bronchospasm is less or negligible.
  • Less interference with carbohydrate metabolism.
  • Lower incidence of cold extremities.
  • Impaired exercise performance.
  • Lesser chances of peripheral vascular disease.

Drugs included in it:

Adrenergic Antagonist Drugs Included In It

Adrenergic Antagonist Short Answers

Question 1. Uses of alpha and beta blockers.


Alpha 2 Adrenergic Antagonist

Adrenergic Antagonist Uses Of Alpha And Beta Blockers

Question 2. Prazosin.


It is a potent highly selective α1 blocker

Prazosin Actions:

  • Blocks sympathetically mediated vasoconstriction.
  • Causes fall in BP.
  • Dilates arterioles more than veins which result in decreased peripheral vascular resistance and cardiac output

Prazosin Uses:

  • Hypertension.
  • Left ventricular failure.
  • Raynaud’s disease.
  • Prostatic hypertrophy.
  • Improve urine flow thereby reducing residual urine in the bladder.

Question 3. Timolol.


  • It is a non-selective β blocker.
  • It is short acting.
  • Orally it is a potent β – blocker.
  • Its ocular hypotensive action is smooth and well-sustained.

Timolol Uses:

1. Topically.

  • In the treatment of glaucoma.

2. Orally.

  • Hypertension.
  • Angina
  • Prophylaxis of myocardial infarction.

Alpha 2 Adrenergic Antagonist

Question 4. Name cardioselective p blockers.


  • Cardioselective beta blockers:
  • Metoprolol – bisoprolol – celiprolol
  • Atenolol esmolol – nebivolol.
  • Acebutolol – betaxolol.

Question 5. Propranolol is contraindicated in bronchial asthma Why?


  1. Blockade of β2 receptors of smooth muscles by propranolol causes.
  2. Increases in airway resistance.
  3. Precipitation of acute attacks in asthmatics.
  4. Worsens chronic obstructive lung diseases.
    • Thus, it is contraindicated in bronchial asthma.

Question 6. Labetalol.


Labetalol is the first adrenergic antagonist capable of blocking both α and β receptors.

  • It is effective orally.

Labetalol Actions:

  • Vasodilation
  • Fall in BP
  • Reduction in cardiac output, heart rate, and peripheral vascular resistance.

Alpha 2 Adrenergic Antagonist

Labetalol Uses:

  • Pheochromocytoma.
  • Clonidine withdrawal.
  • Essential hypertension.

Labetalol Adverse effects:

  • Postural hypotension.
  • GI disturbances.

Viva Voce:

Beta-blocker is contraindicated in asthmatic patients

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