Adrenergic Antagonists 2: Beta Blockers
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Questions and Answers

What is the mechanism of action of beta blockers?

  • They block the beta receptor mediated effects of sympathetic stimulation and adrenergic drugs (correct)
  • They stimulate the parasympathetic nervous system
  • They act as agonists at beta receptors
  • They act as antagonists at alpha receptors

    • What is the primary effect of beta 1 receptor stimulation on the heart?

  • Bronchodilatation
  • Uterine relaxation
  • Vasodilatation
  • Tachycardia (correct)

    • What is the effect of beta 2 receptor stimulation on blood vessels?

  • Vasoconstriction
  • Increased peripheral resistance
  • Decreased blood pressure
  • Vasodilatation (correct)

    • What is the effect of beta 1 receptor stimulation on the kidney?

    <p>Increased release of renin</p> Signup and view all the answers

    What is the effect of beta 2 receptor stimulation on the uterus?

    <p>Uterine relaxation</p> Signup and view all the answers

    What is the advantage of selective beta 1 blockers over non-selective beta blockers?

    <p>They are less likely to cause bronchospasm</p> Signup and view all the answers

    What is the effect of propranolol on the heart?

    <p>Decreased heart rate</p> Signup and view all the answers

    What is the effect of beta 1 receptor stimulation on glycogen metabolism?

    <p>Increased glycogenolysis</p> Signup and view all the answers

    What is the effect of beta 2 receptor stimulation on the skeletal muscles?

    <p>Increased glycogenolysis in muscles</p> Signup and view all the answers

    What is the effect of β1 block on heart rate and force of contraction?

    <p>Decrease heart rate and force of contraction</p> Signup and view all the answers

    What is the effect of β2 block on skeletal muscle blood vessels?

    <p>Vasoconstriction</p> Signup and view all the answers

    What is the effect of β-blockers on oxygen requirement of the heart?

    <p>Decrease oxygen requirement</p> Signup and view all the answers

    Which of the following β-blockers has additional vasodilatory effect?

    <p>Labetalol</p> Signup and view all the answers

    What is the effect of β-blockers on renin secretion?

    <p>Decrease renin secretion</p> Signup and view all the answers

    Which of the following is a contraindication for β-blockers?

    <p>Bronchial asthma</p> Signup and view all the answers

    What is the effect of β-blockers on cardiac output?

    <p>Decrease cardiac output</p> Signup and view all the answers

    Which of the following β-blockers has intrinsic sympathomimetic activity?

    <p>Pindolol</p> Signup and view all the answers

    What is the effect of β-blockers on aqueous humor formation?

    <p>Decrease aqueous humor formation</p> Signup and view all the answers

    What is the effect of oxprenolol on heart rate in a patient with ischemic heart disease?

    <p>It decreases the heart rate</p> Signup and view all the answers

    What is the effect of β-blockers on bronchial airway resistance in patients with asthma and COPD?

    <p>It increases bronchial airway resistance</p> Signup and view all the answers

    What is the effect of β-blockers on intraocular pressure in glaucomatous eye?

    <p>It decreases intraocular pressure</p> Signup and view all the answers

    What is the effect of β-blockers on glycogenolysis and glucagon secretion?

    <p>It inhibits glycogenolysis and glucagon secretion</p> Signup and view all the answers

    What is the effect of β-blockers on recovery from hypoglycaemia in diabetics?

    <p>It delays recovery from hypoglycaemia</p> Signup and view all the answers

    What is the effect of β-blockers on HDL and LDL ratio?

    <p>It decreases HDL and LDL ratio</p> Signup and view all the answers

    What is the effect of β-blockers on blood flow to skeletal muscles?

    <p>It decreases blood flow to skeletal muscles</p> Signup and view all the answers

    What is the effect of β-blockers on anxiety symptoms?

    <p>It decreases anxiety symptoms</p> Signup and view all the answers

    What is the effect of β-blockers with intrinsic sympathomimetic activity (ISA) on resting bradycardia?

    <p>It decreases resting bradycardia</p> Signup and view all the answers

    What is the result of up-regulation of β receptors?

    <p>Super-sensitivity to catecholamines</p> Signup and view all the answers

    What is the clinical implication of up-regulation following abrupt withdrawal of β blockers?

    <p>Angina and myocardial infarction</p> Signup and view all the answers

    What is the mechanism of post-synaptic regulation?

    <p>Change in receptor number</p> Signup and view all the answers

    What is the result of down-regulation of β receptors?

    <p>Decreased response to catecholamines</p> Signup and view all the answers

    What is the clinical implication of down-regulation in bronchial asthma?

    <p>Development of tolerance to bronchodilators</p> Signup and view all the answers

    What is the mechanism of pre-synaptic regulation?

    <p>α2 receptor stimulation</p> Signup and view all the answers

    What is the effect of prolonged exposure to an antagonist on receptor number?

    <p>Increase in receptor number</p> Signup and view all the answers

    What is the effect of prolonged exposure to β receptor agonists on receptor number?

    <p>Decrease in receptor number</p> Signup and view all the answers

    What is the reason for not stopping β blockers abruptly?

    <p>Risk of angina and myocardial infarction</p> Signup and view all the answers

    What is the effect of β-blockers on thyrotoxicosis?

    <p>Decreases the symptoms</p> Signup and view all the answers

    What is the main use of esmolol?

    <p>Rapid control of ventricular rate in supraventricular arrhythmias</p> Signup and view all the answers

    What is the main advantage of labetalol?

    <p>It is safer to be used in pregnancy</p> Signup and view all the answers

    What is the main advantage of carvedilol?

    <p>It has antioxidant, antiproliferative, membrane stabilizing, and vasodilatory properties</p> Signup and view all the answers

    What is the main difference between carvedilol and labetalol?

    <p>Carvedilol has antioxidant properties, while labetalol does not</p> Signup and view all the answers

    What is the main advantage of nebivolol?

    <p>It has vasodilating activity and no membrane stabilizing action</p> Signup and view all the answers

    What is a common adverse effect of β-blockers?

    <p>Bradycardia</p> Signup and view all the answers

    What is a potential consequence of abrupt withdrawal of β-blockers after chronic use?

    <p>Rebound hypertension</p> Signup and view all the answers

    What is the effect of β-blockers on lipid profile?

    <p>It increases total triglycerides and LDL, and decreases HDL</p> Signup and view all the answers

    Study Notes

    Adrenergic Antagonists

    • All β-blockers are competitive antagonists, blocking the β receptor mediated effects of sympathetic stimulation and adrenergic drugs.
    • Non-selective β-blockers act at both β1 and β2 receptors, while cardio-selective or selective β-blockers block primarily β1 receptors.
    • There is no absolute selectivity, and it depends on the dose.

    β1 Adrenoceptors

    • Distribution: postsynaptic – heart and juxtaglomerular apparatus in kidney
    • Effect: excitatory
    • Agonists: epinephrine, norepinephrine, dobutamine
    • Antagonists: propranolol, atenolol

    β2 Adrenoceptors

    • Distribution: postsynaptic - lungs, uterus, skeletal muscle, blood vessels
    • Effect: inhibitory
    • Agonists: epinephrine, salbutamol
    • Antagonists: propranolol

    Effects of β Receptor Stimulation

    • β1: tachycardia, increased myocardial contractility, increased release of renin, increased myocardial oxygen requirement
    • β2: vasodilation, bronchodilation, uterine relaxation, glycogenolysis in muscle and liver

    Effects of β Receptor Blockade

    • β1: decrease heart rate and force of contraction, decrease in COP and BP, decrease oxygen requirement
    • β2: slight constriction of skeletal muscle BV, increase in peripheral resistance, bronchospasm, decrease intraocular tension, delay recovery from hypoglycemia

    Classification of β-Blockers

    • Non-selective β-blockers: propranolol, timolol, pindolol, sotalol
    • Cardio-selective (β1-selective) blockers: atenolol, bisoprolol, metoprolol, esmolol, acebutolol, celiprolol, betaxolol, nebivolol
    • β-blockers with additional vasodilatory effect (α1-blocking action): labetalol, carvedilol
    • β-blockers with intrinsic sympathomimetic (partial agonist) activity: pindolol, acebutolol, labetalol, celiprolol, and carteolol
    • β-blockers with membrane stabilizing (local anaesthetic) activity: propranolol, acebutolol, carvedilol, labetalol, metoprolol, pindolol

    Pharmacological Actions of Propranolol

    • CVS: decrease in heart rate, conduction rate, force of contraction, cardiac output, and blood pressure
    • Kidney: decrease in renin release, decrease in production of angiotensin II and aldosterone, decrease in BP
    • Respiratory effects: blockade of β2 receptors, increase in bronchial airway resistance, bronchospasm in patients with asthma and COPD
    • Eye: decrease in secretion of aqueous humour, decrease in intraocular pressure, local anaesthetic action
    • Metabolic effects: inhibition of stress-induced glycogenolysis, decrease in glucagon secretion, delay recovery from hypoglycaemia, masking of warning signs and symptoms of hypoglycaemia
    • Skeletal muscles: decrease in blood flow, skeletal muscle fatigue, inhibition of tremors
    • CNS: decrease in anxiety symptoms, behavioral changes, forgetfulness, increased dreaming, nightmares

    Therapeutic Uses of β-Blockers

    • Esmolol: ultra-short acting selective β blocker, used I.V for rapid control of ventricular rate in supraventricular arrhythmias, and hypertensive emergencies
    • Labetalol: competitive blocker at β1, β2 and α1 adrenergic receptors, used orally for hypertension and I.V for hypertensive emergency, safer to be used in pregnancy and pregnancy-induced hypertension
    • Carvedilol: like labetalol, it blocks β1, β2 and α1 receptors, has antioxidant, antiproliferative, membrane stabilizing and vasodilatory properties, cardioprotective effect, and reduces mortality in patients with CHF
    • Nebivolol: third-generation selective β1 blocker, has vasodilating activity, no membrane stabilizing and intrinsic sympathomimetic action, no unfavourable effects on lipid profile, used for control of hypertension and congestive cardiac failure

    Adverse Effects of β-Blockers

    • Bradycardia
    • Coolness of hands and feet in winter
    • CNS: mild sedation, vivid dreams, and rarely depression
    • Alteration in lipid profile (increase in total TG, LDL, and decrease in HDL)
    • Rebound hypertension, angina, MI can occur by abrupt withdrawal after chronic use
    • Reduced exercise capacity
    • GI upset, nightmares, forgetfulness, sexual distress

    Regulation of Sympathetic Activity

    • Pre-synaptic regulation: immediate, by α2 receptors
    • Post-synaptic regulation: follows prolonged drug use, either increasing or decreasing the receptor number
    • Up-regulation: increase in receptor number, leading to supersensitivity to the agonist when the antagonist is discontinued
    • Clinical implication: following abrupt withdrawal of β-blockers, angina and myocardial infarction (ischemic heart disease) may be precipitated due to increased sympathetic activity.

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    Adrenergic Antagonists 2 PDF

    Description

    This quiz covers the pharmacological actions of propranolol and beta blockers on various systems, their advantages, therapeutic uses, and contraindications.

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