Adrenergic Agonists Quiz

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Questions and Answers

What is the reason for catecholamine-containing solutions to turn pink or brown over time?

Presence of specific enzymes

Exposure to light

Addition of coloring agents

Oxidation of the catecholamine molecule (correct)

What is the primary reason noncatecholamines have longer half-lives compared to catecholamines?

They are not substrates for COMT and metabolize slowly by MAO (correct)

They do not undergo rapid degradation by COMT

They are less polar and cross the blood brain barrier easily

They have a different molecular structure

Which adrenergic agonist is highly selective, acting at B2 receptors only?

Epinephrine

Albuterol (correct)

Isoproterenol

Dopamine

What is the main adverse effect of alpha-1 receptor activation?

Necrosis of tissues Signup and view all the answers

Which receptor activation is associated with reduction of sympathetic outflow to the heart and blood vessels?

Alpha-2 Signup and view all the answers

What effect does overstimulation of B1 receptors have on the heart?

Tachycardia Signup and view all the answers

What is the therapeutic application of B2 receptor activation in the uterus?

Prevention of preterm labor Signup and view all the answers

What is the adverse effect of B2 receptor activation in diabetics?

Hyperglycemia Signup and view all the answers

What is the primary effect of dopamine receptor activation in the kidneys?

Renal vasodilation Signup and view all the answers

Which receptor activation stimulates the heart rate due to beta-1 activation?

Dopamine Signup and view all the answers

What is the primary effect of B1 receptor activation?

Stimulation of the heart Signup and view all the answers

Why are noncatecholamines considerably less polar than catecholamines?

Due to lack of a catechol group Signup and view all the answers

Which type of adrenergic agonist works by promoting norepinephrine release, blocking norepinephrine reuptake, and inhibiting norepinephrine inactivation?

Indirect agonists Signup and view all the answers

Why are adrenergic agonists often referred to as sympathomimetics?

Because their effects are similar to sympathetic nervous system activation Signup and view all the answers

Which enzyme is responsible for the metabolism of catecholamines?

Catechol-O-methyltransferase [COMT] Signup and view all the answers

What prevents catecholamines from crossing the blood-brain barrier?

Their chemistry Signup and view all the answers

Which of the following is a structural component common to all catecholamines?

Hydroxyl groups on two adjacent carbons Signup and view all the answers

What is the main difference between catecholamines and noncatecholamines in terms of their oral use?

Noncatecholamines can be used orally, but catecholamines cannot Signup and view all the answers

What is the mechanism of action of direct adrenergic agonists?

Work on receptor binding Signup and view all the answers

Why are noncatecholamines suitable for oral use compared to catecholamines?

They are resistant to metabolism by enzymes Signup and view all the answers

What is the significance of the amine component in catecholamines?

It is involved in their metabolism by enzymes Signup and view all the answers

How do indirect adrenergic agonists exert their effects?

By affecting norepinephrine activity Signup and view all the answers

What distinguishes the two classes of adrenergic agonists, catecholamines and noncatecholamines?

Their duration of action Signup and view all the answers

What is meant by a catechol group in catecholamines?

A benzene ring with hydroxyl groups on two adjacent carbons Signup and view all the answers

Study Notes

Catecholamine-Containing Solutions

Catecholamine-containing solutions turn pink or brown over time due to oxidation.

Half-Lives of Adrenergic Agonists

Noncatecholamines have longer half-lives compared to catecholamines because they are less susceptible to enzyme degradation.

Adrenergic Agonists

Salbutamol is a highly selective adrenergic agonist, acting at β2 receptors only.
α1 receptor activation is associated with vasoconstriction.
β2 receptor activation in the uterus is used for therapeutic application, such as tocolysis.
β2 receptor activation in diabetics can cause hypokalemia.
Dopamine receptor activation in the kidneys increases renal blood flow and Na+ excretion.
β1 receptor activation stimulates heart rate.
β1 receptor activation increases contractility and heart rate.
Noncatecholamines are less polar than catecholamines due to the absence of a catechol group.

Mechanism of Action

Indirect adrenergic agonists, such as amphetamines, work by promoting norepinephrine release, blocking norepinephrine reuptake, and inhibiting norepinephrine inactivation.
Direct adrenergic agonists, such as salbutamol, act directly on adrenergic receptors.

Characteristics of Catecholamines

Catecholamines are unable to cross the blood-brain barrier due to their high polarity.
Catecholamines are metabolized by the enzyme catechol-O-methyltransferase (COMT).
The catechol group (3,4-dihydroxyphenyl) is a structural component common to all catecholamines.
Catecholamines are not suitable for oral use due to their susceptibility to enzyme degradation.
The amine component in catecholamines is responsible for their biological activity.

Differences between Catecholamines and Noncatecholamines

The main difference between catecholamines and noncatecholamines is the presence of a catechol group, which affects their polarity and susceptibility to enzyme degradation.

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Description

Test your knowledge about adrenergic agonists and their mechanisms of action. Explore the effects of direct and indirect activation of adrenergic receptors by drugs like dopamine, epinephrine, isoproterenol, and ephedrine.