Beta-Blockers Pharmacokinetics and Effects Quiz
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Questions and Answers

What is the recommended action regarding β-antagonist therapy throughout the periop period?

  • Continuation to maintain desired drug effects (correct)
  • Abrupt discontinuation to maintain drug effects
  • Discontinuation to prevent SNS hyperactivity
  • Switching to a different antagonist

    • How do β-Adrenergic receptor antagonists act on β-adrenergic receptors?

  • By stimulating G proteins
  • Through competitive inhibition (correct)
  • By activating protein kinases
  • By inhibiting adenylate cyclase

    • What effect does chronic use of β-adrenergic antagonists have on the number of β-adrenergic receptors?

  • No change in the number of receptors
  • Decrease in the number of receptors
  • Increase in the number of receptors (correct)
  • No effect on the number of receptors

    • What is the role of cAMP in the mechanism of action of β-Adrenergic receptor antagonists?

    <p>Activates protein kinases</p> Signup and view all the answers

    What is the effect of competitive antagonism on the dose-response curve for the agonist?

    <p>Rightward shift</p> Signup and view all the answers

    Which drug serves as the standard β-adrenergic antagonist against which other β-adrenergic antagonists are often compared?

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

    What do β-Adrenergic receptors stimulate when agonists like epinephrine and norepinephrine bind to them?

    <p>G proteins</p> Signup and view all the answers

    What limits the amount of metoprolol reaching the systemic circulation after oral administration?

    <p>Extensive first-pass hepatic metabolism</p> Signup and view all the answers

    Which receptor does metoprolol selectively antagonize?

    <p>β1-adrenergic receptor</p> Signup and view all the answers

    What effect does metoprolol have on inotropic and chronotropic responses to β-adrenergic stimulation?

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

    At large doses, what is the likely effect of metoprolol on β2 receptors?

    <p>Exerts antagonist effects</p> Signup and view all the answers

    What is the impact of metoprolol on patients with chronic obstructive airway disease or peripheral vascular disease (PVD)?

    <p>Less likely to cause adverse effects</p> Signup and view all the answers

    How does metoprolol affect patients vulnerable to hypoglycemia?

    <p>Less likely to cause adverse effects</p> Signup and view all the answers

    What is the impact of metoprolol on airway resistance in asthmatics?

    <p>Increases, but less than propranolol</p> Signup and view all the answers

    How are metoprolol-induced increases in airway resistance more readily reversed?

    <p>With β2-adrenergic agonists</p> Signup and view all the answers

    What is the impact of substantial hepatic first-pass metabolism on the amount of propranolol reaching the systemic circulation?

    <p>Only about 40% reaches the systemic circulation</p> Signup and view all the answers

    What impact does simultaneous β2-receptor blockade by propranolol have?

    <p>Increases peripheral vascular resistance, including coronary vascular resistance</p> Signup and view all the answers

    How does chronic propranolol treatment impact pulmonary first-pass uptake of fentanyl?

    <p>Reduces pulmonary first-pass uptake of fentanyl</p> Signup and view all the answers

    What is the primary route of clearance for propranolol from the plasma?

    <p>Hepatic metabolism</p> Signup and view all the answers

    What is the impact of changes in protein binding on propranolol's pharmacokinetics?

    <p>Changes in protein binding can impact its pharmacokinetics</p> Signup and view all the answers

    What distinguishes the duration of heart rate reduction compared to negative inotropic effects of propranolol?

    <p>Heart rate reduction has a longer-lasting effect</p> Signup and view all the answers

    What is the impact of propranolol on systolic ejection time and ventricular dilatation?

    <p>May paradoxically increase systolic ejection time and ventricular dilatation</p> Signup and view all the answers

    What is the impact of systemic absorption of timolol?

    <p>Can cause bradycardia and increased airway resistance</p> Signup and view all the answers

    Which receptor subtype is predominantly found in the myocardium?

    <p>β1</p> Signup and view all the answers

    What is the main action of β1 receptors in the heart?

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

    Which β-adrenergic antagonist is suitable for patients with asthma and reactive airway disease?

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

    Which β-adrenergic antagonist has no intrinsic sympathomimetic activity and equally antagonizes both β1 and β2 receptors?

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

    Which β-adrenergic antagonist has a brief elimination half-time of about 10 minutes?

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

    Which β-adrenergic antagonist is a reference standard against which other β-adrenergic antagonists are often compared?

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

    Which receptor blockade leads to reduced heart rate, slower conduction through the AV node, and decreased inotropy?

    <p>β1</p> Signup and view all the answers

    What is the main action of β1 receptors?

    <p>Increasing heart rate, contractility, and conduction</p> Signup and view all the answers

    Which condition is suitable for treatment with cardioselective β-adrenergic antagonists?

    <p>Reactive airway disease</p> Signup and view all the answers

    What is the primary use of beta-2 blockers like propranolol?

    <p>Migraine prophylaxis</p> Signup and view all the answers

    What is the impact of β1-receptor blockade?

    <p>Reduced heart rate, slower conduction, decreased contractility</p> Signup and view all the answers

    What is a key consideration in determining dosing intervals for β-adrenergic antagonists?

    <p>Half-life</p> Signup and view all the answers

    What is the main impact of β2-receptor blockade?

    <p>Increased risk of bronchospasm and worsened symptoms of peripheral vascular disease</p> Signup and view all the answers

    What is the primary role of carvedilol?

    <p>Decreasing myocardial oxygen demand in non-decompensated heart failure</p> Signup and view all the answers

    Study Notes

    Beta-Blockers Pharmacokinetics and Effects

    • Propranolol reduces heart rate and myocardial contractility by blocking β1 receptors, leading to decreased cardiac output.
    • Propranolol has a longer-lasting heart rate reduction compared to its negative inotropic effects, indicating potential distinctions in β1 receptors.
    • Simultaneous β2-receptor blockade by propranolol increases peripheral vascular resistance, including coronary vascular resistance.
    • Propranolol may paradoxically increase systolic ejection time and ventricular dilatation, raising myocardial oxygen demand, but its oxygen-sparing effects generally outweigh these changes.
    • Propranolol exhibits extensive binding to plasma proteins (90-95%), and changes in protein binding can impact its pharmacokinetics.
    • Propranolol is primarily cleared from the plasma through hepatic metabolism, with significant individual variation in the extent of hepatic first-pass metabolism.
    • Propranolol reduces the clearance of amide local anesthetics by affecting hepatic blood flow and inhibiting liver metabolism, potentially increasing systemic toxicity of certain amide local anesthetics.
    • Chronic propranolol treatment reduces pulmonary first-pass uptake of fentanyl, leading to a greater amount of injected fentanyl entering the systemic circulation.
    • Nadolol is a non-selective beta-antagonist with a long duration of action and exhibits slow and incomplete absorption from the gastrointestinal tract.
    • Pindolol has a shorter elimination half-time but this duration can be prolonged in patients with renal failure.
    • Timolol, a nonselective β-adrenergic receptor antagonist, is as effective as propranolol and is administered as eye drops in the treatment of glaucoma.
    • Systemic absorption of timolol can cause bradycardia and increased airway resistance, and it has been associated with impaired control of ventilation in neonates.

    Beta-Adrenergic Antagonists: Key Facts and Pharmacokinetics

    • Beta-adrenergic stimulation in the heart results in positive and negative effects, including increased heart rate, contractility, and conduction, and decreased relaxation, with around 75% of myocardial β receptors being β1 receptors.
    • The main action of β1 receptors is in the heart, kidneys, and adipose tissue, leading to increased heart rate, contractility, and conduction.
    • Beta-1 blockers target the heart, kidneys, and JG cells, slowing heart rate, treating arrhythmias, and decreasing myocardial oxygen demand.
    • Beta-2 blockers, like propranolol, are used to treat variceal bleeding, migraine prophylaxis, and to alleviate tremors.
    • The third-generation nonselective beta-blocker, carvedilol, is used for non-decompensated heart failure to decrease myocardial oxygen demand.
    • The chemical structure of β-adrenergic antagonists, derived from isoproterenol, determines whether they act as antagonists or agonists at β-adrenergic receptors.
    • β-Adrenergic antagonists are categorized into nonselective and cardioselective groups, with varying degrees of selectivity based on dosage and intrinsic sympathomimetic activity.
    • Cardioselective β-adrenergic antagonists are suitable for patients with asthma and reactive airway disease due to their reduced impact on peripheral β2 receptors.
    • β1-receptor blockade results in reduced heart rate, slower conduction, decreased contractility, increased ability to relax, and reduced ability to initiate electrical impulses, leading to a decrease in myocardial oxygen demand and improved myocardial blood flow.
    • β2-receptor blockade can increase the risk of bronchospasm and worsen symptoms of peripheral vascular disease.
    • β-Adrenergic antagonists vary in pharmacokinetics, with esmolol having a brief half-time of about 10 minutes and propranolol and nebivolol being highly protein-bound.
    • Understanding elimination half-time is crucial in determining dosing intervals, and therapeutic plasma concentrations can vary significantly among these drugs and patients due to various factors.

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    Description

    Test your knowledge of beta-blockers pharmacokinetics and effects with this quiz. Explore the mechanisms of action, pharmacokinetic properties, and clinical implications of propranolol, nadolol, pindolol, and timolol.

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