Adrenergic Agonists and Receptor Activation
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Questions and Answers

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

  • Ephedrine (correct)
  • Epinephrine
  • Dopamine
  • Isoproterenol
  • Which enzyme is responsible for the metabolism of catecholamines like epinephrine and norepinephrine?

  • Amylase
  • Catechol-O-methyltransferase (correct)
  • Protease
  • Lipase
  • What is the main reason that catecholamines cannot be used orally?

  • They have a brief duration of action
  • They contain a catechol group and an amine group
  • They cannot cross the blood-brain barrier
  • They are quickly metabolized by enzymes (correct)
  • Which class of adrenergic agonists includes drugs like dopamine, epinephrine, isoproterenol, and ephedrine?

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

    What is the defining feature of noncatecholamines that distinguishes them from catecholamines?

    <p>They can cross the blood-brain barrier</p> Signup and view all the answers

    What is the common property shared by all catecholamines due to their chemistry?

    <p>They have a brief duration of action</p> Signup and view all the answers

    Which adrenergic agonist works on receptor binding and is considered a direct agonist?

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

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

    <p>They contain a benzene ring with hydroxyl groups on two adjacent carbons</p> Signup and view all the answers

    What differentiates noncatecholamines from catecholamines?

    <p>They have a longer duration of action</p> Signup and view all the answers

    What is the defining characteristic of catecholamines?

    <p>They contain a benzene ring with hydroxyl groups on two adjacent carbons</p> Signup and view all the answers

    Which enzyme metabolizes catecholamines like epinephrine and norepinephrine?

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

    What is the reason that catecholamines are ineffective if given orally?

    <p>They are inactivated before reaching systemic circulation</p> Signup and view all the answers

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

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

    What distinguishes noncatecholamines from catecholamines in terms of metabolism?

    <p>Noncatecholamines are not substrates for COMT and metabolize slowly by MAO</p> Signup and view all the answers

    Which drug is highly selective, acting at B2 receptors only?

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

    At low doses, which drug acts on B2 receptors only, but at high doses, it also acts on B1 and B2 receptors?

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

    Which response can be elicited by the activation of A1 receptors in blood vessels?

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

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

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

    Activation of beta-1 receptors stimulates which organ?

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

    What is the therapeutic application of beta-1 agonists?

    <p>Heart failure</p> Signup and view all the answers

    Where are beta-2 receptors primarily located?

    <p>Lungs and uterus</p> Signup and view all the answers

    What effect does the activation of alpha-2 receptors in the central nervous system produce?

    <p>Reduction of sympathetic outflow to the heart and blood vessels, and relief of severe pain</p> Signup and view all the answers

    Which receptor subtype does epinephrine act on?

    <p>A1, A2, B1, B2</p> Signup and view all the answers

    Study Notes

    Adrenergic Agonists

    • Cocaine works by promoting norepinephrine release, blocking norepinephrine reuptake, and inhibiting norepinephrine inactivation.

    Catecholamine Metabolism

    • Catechol-O-methyltransferase (COMT) is responsible for the metabolism of catecholamines like epinephrine and norepinephrine.

    Catecholamine Administration

    • Catecholamines cannot be used orally because they are ineffective when given orally.

    Classes of Adrenergic Agonists

    • The class of adrenergic agonists that includes drugs like dopamine, epinephrine, isoproterenol, and ephedrine is called catecholamines.

    Characteristics of Catecholamines

    • The defining feature of noncatecholamines is that they are not inactivated by COMT, distinguishing them from catecholamines.
    • The common property shared by all catecholamines due to their chemistry is that they are inactivated by COMT.
    • The defining characteristic of catecholamines is that they are inactivated by COMT.

    Pharmacology of Adrenergic Agonists

    • Direct agonists work on receptor binding, and examples include epinephrine and isoproterenol.
    • Catecholamines are unable to cross the blood-brain barrier due to their chemical structure.
    • Noncatecholamines are differentiated from catecholamines in terms of metabolism, as they are not inactivated by COMT.

    Enzymatic Metabolism

    • COMT metabolizes catecholamines like epinephrine and norepinephrine.
    • The reason catecholamines are ineffective when given orally is that they are metabolized by COMT.

    Oxidation of Catecholamines

    • The pigmentation of catecholamine-containing solutions over time is caused by oxidation.

    Receptor Pharmacology

    • Salbutamol is highly selective, acting at B2 receptors only.
    • At low doses, salmeterol acts on B2 receptors only, but at high doses, it also acts on B1 and B2 receptors.
    • The activation of A1 receptors in blood vessels can elicit vasoconstriction.
    • The primary adverse effect of alpha-1 receptor activation is hypertension.
    • Activation of beta-1 receptors stimulates the heart.
    • The therapeutic application of beta-1 agonists is in the treatment of heart failure.
    • Beta-2 receptors are primarily located in the lungs.
    • The activation of alpha-2 receptors in the central nervous system produces a decrease in sympathetic tone.
    • Epinephrine acts on alpha-1, alpha-2, beta-1, and beta-2 receptors.

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    Test your knowledge on the mechanisms and drugs involved in adrenergic receptor activation, including direct and indirect agonists. Learn about the effects and similarities to sympathetic nervous system activation.

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