Podcast
Questions and Answers
What is the recommended action regarding β-antagonist therapy throughout the periop period?
What is the recommended action regarding β-antagonist therapy throughout the periop period?
How do β-Adrenergic receptor antagonists act on β-adrenergic receptors?
How do β-Adrenergic receptor antagonists act on β-adrenergic receptors?
What effect does chronic use of β-adrenergic antagonists have on the number of β-adrenergic receptors?
What effect does chronic use of β-adrenergic antagonists have on the number of β-adrenergic receptors?
What is the role of cAMP in the mechanism of action of β-Adrenergic receptor antagonists?
What is the role of cAMP in the mechanism of action of β-Adrenergic receptor antagonists?
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What is the effect of competitive antagonism on the dose-response curve for the agonist?
What is the effect of competitive antagonism on the dose-response curve for the agonist?
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Which drug serves as the standard β-adrenergic antagonist against which other β-adrenergic antagonists are often compared?
Which drug serves as the standard β-adrenergic antagonist against which other β-adrenergic antagonists are often compared?
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What do β-Adrenergic receptors stimulate when agonists like epinephrine and norepinephrine bind to them?
What do β-Adrenergic receptors stimulate when agonists like epinephrine and norepinephrine bind to them?
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What limits the amount of metoprolol reaching the systemic circulation after oral administration?
What limits the amount of metoprolol reaching the systemic circulation after oral administration?
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Which receptor does metoprolol selectively antagonize?
Which receptor does metoprolol selectively antagonize?
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What effect does metoprolol have on inotropic and chronotropic responses to β-adrenergic stimulation?
What effect does metoprolol have on inotropic and chronotropic responses to β-adrenergic stimulation?
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At large doses, what is the likely effect of metoprolol on β2 receptors?
At large doses, what is the likely effect of metoprolol on β2 receptors?
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What is the impact of metoprolol on patients with chronic obstructive airway disease or peripheral vascular disease (PVD)?
What is the impact of metoprolol on patients with chronic obstructive airway disease or peripheral vascular disease (PVD)?
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How does metoprolol affect patients vulnerable to hypoglycemia?
How does metoprolol affect patients vulnerable to hypoglycemia?
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What is the impact of metoprolol on airway resistance in asthmatics?
What is the impact of metoprolol on airway resistance in asthmatics?
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How are metoprolol-induced increases in airway resistance more readily reversed?
How are metoprolol-induced increases in airway resistance more readily reversed?
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What is the impact of substantial hepatic first-pass metabolism on the amount of propranolol reaching the systemic circulation?
What is the impact of substantial hepatic first-pass metabolism on the amount of propranolol reaching the systemic circulation?
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What impact does simultaneous β2-receptor blockade by propranolol have?
What impact does simultaneous β2-receptor blockade by propranolol have?
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How does chronic propranolol treatment impact pulmonary first-pass uptake of fentanyl?
How does chronic propranolol treatment impact pulmonary first-pass uptake of fentanyl?
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What is the primary route of clearance for propranolol from the plasma?
What is the primary route of clearance for propranolol from the plasma?
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What is the impact of changes in protein binding on propranolol's pharmacokinetics?
What is the impact of changes in protein binding on propranolol's pharmacokinetics?
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What distinguishes the duration of heart rate reduction compared to negative inotropic effects of propranolol?
What distinguishes the duration of heart rate reduction compared to negative inotropic effects of propranolol?
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What is the impact of propranolol on systolic ejection time and ventricular dilatation?
What is the impact of propranolol on systolic ejection time and ventricular dilatation?
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What is the impact of systemic absorption of timolol?
What is the impact of systemic absorption of timolol?
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Which receptor subtype is predominantly found in the myocardium?
Which receptor subtype is predominantly found in the myocardium?
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What is the main action of β1 receptors in the heart?
What is the main action of β1 receptors in the heart?
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Which β-adrenergic antagonist is suitable for patients with asthma and reactive airway disease?
Which β-adrenergic antagonist is suitable for patients with asthma and reactive airway disease?
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Which β-adrenergic antagonist has no intrinsic sympathomimetic activity and equally antagonizes both β1 and β2 receptors?
Which β-adrenergic antagonist has no intrinsic sympathomimetic activity and equally antagonizes both β1 and β2 receptors?
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Which β-adrenergic antagonist has a brief elimination half-time of about 10 minutes?
Which β-adrenergic antagonist has a brief elimination half-time of about 10 minutes?
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Which β-adrenergic antagonist is a reference standard against which other β-adrenergic antagonists are often compared?
Which β-adrenergic antagonist is a reference standard against which other β-adrenergic antagonists are often compared?
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Which receptor blockade leads to reduced heart rate, slower conduction through the AV node, and decreased inotropy?
Which receptor blockade leads to reduced heart rate, slower conduction through the AV node, and decreased inotropy?
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What is the main action of β1 receptors?
What is the main action of β1 receptors?
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Which condition is suitable for treatment with cardioselective β-adrenergic antagonists?
Which condition is suitable for treatment with cardioselective β-adrenergic antagonists?
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What is the primary use of beta-2 blockers like propranolol?
What is the primary use of beta-2 blockers like propranolol?
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What is the impact of β1-receptor blockade?
What is the impact of β1-receptor blockade?
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What is a key consideration in determining dosing intervals for β-adrenergic antagonists?
What is a key consideration in determining dosing intervals for β-adrenergic antagonists?
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What is the main impact of β2-receptor blockade?
What is the main impact of β2-receptor blockade?
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What is the primary role of carvedilol?
What is the primary role of carvedilol?
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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.
