Adrenergic Agonists: Direct and Indirect Mechanisms

What is the main reason why catecholamines administered orally are ineffective?

They are quickly metabolized by MAO and COMT. (correct)

They cause vasoconstriction in blood vessels.

They cannot cross the blood brain barrier.

They cause mydriasis.

Which characteristic of noncatecholamines allows them to have longer half-lives compared to catecholamines?

They do not undergo rapid degradation by MAO and COMT. (correct)

They can cause vasoconstriction in blood vessels.

They are substrates for COMT.

They are polar and cannot cross the blood brain barrier.

At low doses, which adrenergic agonist acts primarily on B2 receptors only?

Isoproterenol

Epinephrine

Albuterol (correct)

Dopamine

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

Tachycardia Signup and view all the answers

What is the clinical significance of activation of alpha-2 receptors in the central nervous system?

Relief of severe pain. Signup and view all the answers

What is the primary therapeutic application of B1 agonists?

Stimulation of the heart. Signup and view all the answers

What is a potential adverse effect of B2 receptor activation in the uterus?

Hyperglycemia Signup and view all the answers

What effect does activation of dopamine receptors have on renal vasculature?

Renal vasodilation Signup and view all the answers

What is the primary reason why albuterol is considered highly selective when acting at low doses?

It has minimal impact on the heart rate. Signup and view all the answers

Which receptor activation leads to relief of severe pain?

Alpha-2 receptors Signup and view all the answers

What is the primary therapeutic application for activation of B2 receptors in the uterus?

Treatment of preterm labor. Signup and view all the answers

What can overstimulation of B1 receptors lead to in some cases?

Tachycardia Signup and view all the answers

Which type of adrenergic agonists work by promotion of norepinephrine release, blockade of norepinephrine reuptake, and inhibition of norepinephrine inactivation?

Indirect agonists Signup and view all the answers

What is the main difference between catecholamines and noncatecholamines?

Their availability for oral use Signup and view all the answers

Why are catecholamines unable to cross the blood-brain barrier?

As they contain a catechol group and an amine group Signup and view all the answers

Which enzyme quickly metabolizes catecholamines?

Monoamine oxidase [MAO] Signup and view all the answers

What is the defining feature of indirect adrenergic agonists?

Their promotion of norepinephrine release Signup and view all the answers

What is the chemical structure that characterizes catecholamines?

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

Why do catecholamines have a brief duration of action?

Due to their chemical structure Signup and view all the answers

Which class of adrenergic agonists includes dopamine, epinephrine, isoproterenol, and ephedrine?

Catecholamines Signup and view all the answers

What do noncatecholamines have in common?

They cannot cross the blood-brain barrier Signup and view all the answers