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Questions and Answers
Which receptor activation is primarily responsible for vasoconstriction?
Which receptor activation is primarily responsible for vasoconstriction?
What is a common side effect of Alpha-1 receptor activation?
What is a common side effect of Alpha-1 receptor activation?
Which of the following effects is associated with Alpha-2 receptor agonists?
Which of the following effects is associated with Alpha-2 receptor agonists?
Which agent is commonly used to delay the absorption of local anesthetics?
Which agent is commonly used to delay the absorption of local anesthetics?
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What differentiates catecholamines from noncatecholamines regarding their metabolism?
What differentiates catecholamines from noncatecholamines regarding their metabolism?
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Which statement regarding beta-1 agonists is true in the context of heart failure?
Which statement regarding beta-1 agonists is true in the context of heart failure?
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What is the presynaptic receptor that provides negative feedback on NE release?
What is the presynaptic receptor that provides negative feedback on NE release?
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What is the primary therapeutic use of beta-2 receptor agonists?
What is the primary therapeutic use of beta-2 receptor agonists?
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What is the primary action of beta-2 agonists in the treatment of asthma?
What is the primary action of beta-2 agonists in the treatment of asthma?
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Which beta-1 agonist adverse effect is particularly concerning for patients with coronary artery issues?
Which beta-1 agonist adverse effect is particularly concerning for patients with coronary artery issues?
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What pharmacological role does epinephrine play in anaphylactic reactions?
What pharmacological role does epinephrine play in anaphylactic reactions?
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What is a significant effect of beta-2 agonists at high doses?
What is a significant effect of beta-2 agonists at high doses?
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Which agent is most commonly used to treat narcolepsy in children?
Which agent is most commonly used to treat narcolepsy in children?
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What adverse effect is associated with alpha-2 agonists?
What adverse effect is associated with alpha-2 agonists?
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What should be monitored when a patient is taking MAO inhibitors with tyramine?
What should be monitored when a patient is taking MAO inhibitors with tyramine?
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In the treatment of glaucoma, which medication is used?
In the treatment of glaucoma, which medication is used?
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Which of the following is a natural catecholamine?
Which of the following is a natural catecholamine?
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What is the mode of action of non-catecholamines such as phenylephrine?
What is the mode of action of non-catecholamines such as phenylephrine?
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Which adrenergic receptors does dobutamine primarily interact with?
Which adrenergic receptors does dobutamine primarily interact with?
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What is a significant adverse effect associated with sympathomimetic drugs?
What is a significant adverse effect associated with sympathomimetic drugs?
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Which drug is an example of a mixed-acting sympathomimetic agent?
Which drug is an example of a mixed-acting sympathomimetic agent?
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Which chemical structure is characteristic of catecholamines?
Which chemical structure is characteristic of catecholamines?
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Which sympathomimetic drug is primarily utilized as a beta-2 agonist?
Which sympathomimetic drug is primarily utilized as a beta-2 agonist?
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How does reserpine affect the action of sympathomimetic drugs?
How does reserpine affect the action of sympathomimetic drugs?
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Which of the following is a synthetic catecholamine?
Which of the following is a synthetic catecholamine?
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Which sympathomimetic drug is known for its ability to enter the CNS?
Which sympathomimetic drug is known for its ability to enter the CNS?
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Study Notes
Sympathomimetic Drugs
- Sympathomimetic drugs, also known as adrenergic agonists, mimic the effects of the sympathetic nervous system.
- They can be classified based on their chemical structure (catecholamines or non-catecholamines) and their mode of action (direct or indirect).
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Catecholamines are derived from the amino acid tyrosine and include:
- Natural: epinephrine, norepinephrine, dopamine
- Synthetic: isoproterenol, dobutamine
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Non-catecholamines are not derived from tyrosine and include:
- Directly acting: methoxamine, phenylephrine, clonidine, terbutaline, oxymetazoline
- Indirectly acting: tyramine, mephentermine
- Mixed: ephedrine
Mode of Action
- Directly acting sympathomimetics bind to and activate adrenergic receptors.
- Indirectly acting sympathomimetics work by releasing stored norepinephrine (NE) from nerve terminals.
- Mixed action sympathomimetics have both direct and indirect actions.
Effects of Pre-Treatment with Cocaine or Reserpine
- Cocaine blocks the reuptake of NE, increasing its concentration in the synapse and enhancing the effects of directly acting sympathomimetics.
- It has no effect on indirectly acting sympathomimetics since they don't rely on NE reuptake.
- Reserpine depletes NE stores by inhibiting its storage in vesicles, thus reducing the effectiveness of both direct and indirect acting sympathomimetics.
Receptor Selectivity - Key Facts
- Alpha-1 receptors: Primarily located on blood vessels and cause vasoconstriction.
- Alpha-2 receptors: Found in the central nervous system (CNS) and suppress sympathetic outflow, leading to decreased blood pressure.
- Beta-1 receptors: primarily located in the heart and cause increased heart rate and contractility.
- Beta-2 receptors: located in the bronchioles, causing bronchodilation, and in the uterus, causing relaxation.
Therapeutic Uses of Sympathomimetics
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Alpha-1:
- Vasoconstriction: control superficial bleeding, decongestion, delay absorption of local anesthetics.
- Mydriasis: dilate pupils for ophthalmic procedures.
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Alpha-2:
- Antihypertensive: reduce blood pressure by decreasing sympathetic outflow.
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Beta-1:
- Inotropic effect: increase cardiac contractility in heart failure and shock.
- Increase conduction through the AV node in atrioventricular block.
- Restore cardiac rhythm after arrest.
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Beta-2:
- Bronchodilation: relieve bronchospasm in asthma.
- Inhibit uterine contractions: prevent preterm labor.
Adverse Effects
- Alpha-1: Hypertension, necrosis
- Alpha-2: Hypotension, withdrawal syndrome
- Beta-1: Tachycardia, arrhythmias, angina
- Beta-2: Hyperglycemia, tremors, tachycardia (at high doses)
Non-Catecholamine Sympathomimetics
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Amphetamine:
- Powerful CNS stimulant: used in ADHD and narcolepsy.
- Peripheral effects similar to NE, but with a longer duration of action due to resistance to metabolism.
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Ephedrine:
- Mixed action sympathomimetic acting both directly and indirectly.
- Weak CNS stimulant.
- Therapeutic use: bronchodilator.
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Tyramine:
- Found in certain foods and can cause hypertensive crises in patients taking MAO inhibitors (antidepressants).
- Pure indirect effect, releasing NE from vesicles.
Important Points
- Catecholamines have a shorter duration of action because they are readily metabolized by MAO and COMT.
- Non-catecholamines are less readily metabolized, allowing for longer effects.
- Catecholamines are highly polar and cannot easily cross the blood-brain barrier, limiting their CNS effects.
- Non-catecholamines are less polar and can enter the CNS.
- Receptor selectivity is never absolute, meaning that drugs may activate multiple receptor types at high doses.
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Description
This quiz covers sympathomimetic drugs, also known as adrenergic agonists, and their classification based on chemical structure and mode of action. Learn about catecholamines, non-catecholamines, and how these drugs interact with adrenergic receptors in the sympathetic nervous system.
