Questions and Answers
What is the primary off-label use of terbutaline?
Which side effect is commonly associated with β agonist agents such as terbutaline?
What is a significant risk when using monoamine oxidase inhibitors (MAOIs) with β agonists?
How long does a single dose of salmeterol or formoterol provide bronchodilation?
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Why should mirabegron be used cautiously in certain patients?
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Which characteristic is NOT associated with catecholamines?
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What characterizes the pharmacokinetics of non-catecholamines like phenylephrine and ephedrine?
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What structural feature greatly affects the potency of adrenergic drugs?
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Which of the following agents is classified as a direct-acting agonist?
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Why do catecholamines have a brief period of action when administered parenterally?
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Which mechanism characterizes indirect-acting adrenergic agonists?
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Which of the following is a characteristic of non-catecholamines?
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What common side effects are attributable to catecholamine action on the CNS?
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Which of the following is a characteristic of mixed-action agonists?
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How does the structure of adrenergic drugs impact their ability to differentiate between α and β receptors?
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Which of the following statements is true about the metabolic pathway of adrenergic agonists?
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Which agent is specifically mentioned as causing the release of norepinephrine?
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Which of the following statements about catecholamines is true?
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Which option includes both types of adrenergic agonists?
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Which combination of features contributes to the effectiveness of adrenergic agonists?
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Which is a common feature of adrenergic agonists with greater lipid solubility?
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What effect does norepinephrine have on blood vessels compared to epinephrine?
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Which therapeutic use is primarily associated with norepinephrine?
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What physiological response is triggered by increased vagal activity due to norepinephrine?
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How does atropine influence the effects of norepinephrine on the heart?
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Isoproterenol is known for its action on which receptors?
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Which of the following best describes the action of isoproterenol?
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What drawback is associated with isoproterenol's non-selectivity?
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What physiological change occurs when norepinephrine increases blood pressure?
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What can happen if a patient taking MAOIs consumes substances that are ordinarily oxidized by MAO?
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How does cocaine affect norepinephrine levels in the synaptic space?
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Which of the following is NOT a characteristic of ephedrine and pseudoephedrine?
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What effect does ephedrine have on blood pressure?
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What distinguishes cocaine from other local anesthetics?
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In comparison to epinephrine, how does the potency of ephedrine in producing bronchodilation measure up?
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Which characteristic applies to both ephedrine and pseudoephedrine?
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What is the typical primary action of mixed-action adrenergic agents like ephedrine?
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Study Notes
Characteristics of Adrenergic Agonists
- Adrenergic drugs primarily derive from β-phenylethylamine, varying based on side chain and benzene ring modifications.
- Key features affecting receptor interaction: number/position of OH substitutions on the benzene ring and nature of amino nitrogen substituents.
Catecholamines
- Include epinephrine, norepinephrine, isoproterenol, and dopamine.
- High potency due to presence of -OH groups at positions 3 and 4 on the benzene ring.
- Metabolized quickly by Catechol-O-methyltransferase (COMT) and Monoamine oxidase (MAO), resulting in brief action when given parenterally and ineffectiveness when administered orally.
- Polar nature results in poor central nervous system (CNS) penetration but can cause CNS-related side effects (e.g., anxiety, tremors).
Non-Catecholamines
- Lack catechol hydroxyl groups, leading to longer half-lives due to less susceptibility to COMT inactivation.
- Examples include phenylephrine, ephedrine, and amphetamine.
- Increased lipid solubility enhances CNS access and prolongs duration of action.
Mechanism of Action
- Direct-acting agonists: Stimulate α or β receptors directly; examples include epinephrine and norepinephrine.
- Indirect-acting agonists: Block norepinephrine reuptake or promote its release; examples include cocaine (reuptake inhibitor) and amphetamines (release promoters).
- Mixed-action agonists: Stimulate receptors and release norepinephrine; examples are ephedrine and pseudoephedrine.
Norepinephrine
- Causes significant vasoconstriction without compensatory vasodilation, making it less suitable for asthma treatment.
- Increases blood pressure and stimulates baroreceptors, leading to bradycardia through vagal activity, which can be counteracted by atropine.
- Therapeutically used for shock treatment by increasing vascular resistance and blood pressure.
Isoproterenol
- A synthetic catecholamine stimulating both β1 and β2 receptors, rarely used due to non-selectivity.
- Increases heart rate, contractility, and cardiac output comparably to epinephrine.
- Side effects include tremor and may lead to tachycardia or arrhythmia, particularly in patients with existing heart conditions.
Salmeterol and Formoterol
- Long-acting β agonists (LABAs) selective for β2 receptors.
- Provide prolonged bronchodilation (up to 12 hours) compared to albuterol.
- Recommended in combination with corticosteroids, not monotherapy.
Mirabegron
- A β3 agonist that relaxes detrusor smooth muscle, increasing bladder capacity, and used for overactive bladder treatment.
- May raise blood pressure, contraindicated in patients with uncontrolled hypertension.
Cocaine
- Unique as a local anesthetic that blocks norepinephrine transporter, enhancing sympathetic activity.
- Accumulated norepinephrine leads to magnified effects of catecholamines and prolonged action duration.
Mixed-Action Adrenergic Agonists
- Ephedrine and pseudoephedrine stimulate α and β receptors while releasing stored norepinephrine.
- Both exhibit long durations of action and good oral absorption, but are less potent than epinephrine.
- Used to treat hypotension through vasoconstriction and cardiac stimulation, while inducing slower-acting bronchodilation compared to other catecholamines.
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Description
In this quiz, you will explore the characteristics and structural features of adrenergic agonists as discussed in Pharmacology Lecture 6 by Dr. Salem Abukres. Understand the role of these compounds in affecting alpha and beta receptors. Test your knowledge on the derivatives of β-phenylethylamine and their impact on the central nervous system.