Adrenergic Agonists and Receptor Activation
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Questions and Answers

Which type of adrenergic agonists work by promotion of norepinephrine release?

  • Noncatacholamines
  • Catecholamines
  • Direct agonists
  • Indirect agonists (correct)
  • What is the defining feature that differentiates catecholamines from noncatacholamines?

  • Chemical structure (correct)
  • Availability for oral use
  • Ability to cross the blood-brain barrier
  • Duration of action
  • Why can't catecholamines be used orally?

  • They lack the necessary chemical structure for oral use
  • They cannot cross the blood-brain barrier
  • They are quickly metabolized by enzymes (correct)
  • They have a brief duration of action
  • Which enzyme quickly metabolizes catecholamines?

    <p>Both A and B</p> Signup and view all the answers

    What is the mechanism of action for direct adrenergic agonists?

    <p>Receptor binding</p> Signup and view all the answers

    What class of adrenergic agonists cannot cross the blood-brain barrier?

    <p>Catecholamines</p> Signup and view all the answers

    Which group contains dopamine, epinephrine, isoproterenol, and ephedrine?

    <p>Catecholamines</p> Signup and view all the answers

    Which enzymes are present in the liver and in the intestinal wall?

    <p>Catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO)</p> Signup and view all the answers

    Why are catecholamines ineffective when given orally?

    <p>They are quickly destroyed by COMT and MAO</p> Signup and view all the answers

    What causes the pink or brown pigmentation of catecholamine-containing solutions over time?

    <p>Oxidation of the catecholamine molecule</p> Signup and view all the answers

    How do noncatecholamines differ from catecholamines in terms of metabolism?

    <p>They lack a catechol group and metabolize slowly by MAO</p> Signup and view all the answers

    What allows noncatecholamines to be given orally?

    <p>They lack a catechol group and can cross the blood brain barrier easily</p> Signup and view all the answers

    Why do noncatecholamines have longer half-lives compared to catecholamines?

    <p>Because they lack a catechol group and metabolize slowly by MAO</p> Signup and view all the answers

    What makes noncatecholamines less polar than catecholamines?

    <p>Their lack of a catechol group</p> Signup and view all the answers

    Study Notes

    Adrenergic Agonists

    • Alpha-2 agonists work by promoting norepinephrine release.

    Catecholamines

    • Defining feature: presence of a catechol group (3,4-dihydroxyphenyl) in their structure.
    • Cannot be used orally because they are rapidly metabolized by COMT (catechol-O-methyltransferase) and MAO (monoamine oxidase).
    • COMT quickly metabolizes catecholamines.

    Mechanism of Action

    • Direct adrenergic agonists work by directly binding to adrenergic receptors.

    Classification

    • Catecholamines: dopamine, epinephrine, isoproterenol, and ephedrine.
    • Noncatecholamines: cannot cross the blood-brain barrier.

    Enzymes

    • COMT and MAO are present in the liver and intestinal wall.

    Ineffective Oral Administration

    • Catecholamines are ineffective when given orally due to rapid metabolism by COMT and MAO.

    Pigmentation

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

    Metabolism

    • Noncatecholamines differ from catecholamines in that they are not metabolized by COMT.

    Oral Administration

    • Noncatecholamines can be given orally because they are not rapidly metabolized by COMT and MAO.

    Half-Lives

    • Noncatecholamines have longer half-lives compared to catecholamines due to slower metabolism.

    Polarity

    • Noncatecholamines are less polar than catecholamines, making them more capable of crossing the blood-brain barrier.

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    Description

    Test your knowledge on adrenergic agonists and the mechanisms of adrenergic receptor activation, including direct and indirect agonists. Learn about the effects of these drugs and how they mimic sympathetic nervous system activation.

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