Adrenergic Agonists and Receptor Activation Quiz
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Questions and Answers

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

  • They undergo rapid degradation by MAO and COMT
  • They are inactivated before they can reach systemic circulation (correct)
  • They lack a catechol group
  • They have a lower affinity for adrenergic receptors

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

  • Bacterial contamination
  • Reaction with light
  • Decomposition of the solution
  • Oxidation of the catecholamine molecule (correct)

    • How do noncatecholamines differ from catecholamines?

  • They undergo rapid degradation by MAO and COMT
  • They have a higher affinity for adrenergic receptors
  • They are substrates for COMT and metabolize slowly by MAO
  • They lack a catechol group and metabolize slowly by MAO (correct)

    • What is a significant characteristic of noncatecholamines in terms of their ability to cross the blood-brain barrier?

    <p>They are considerably less polar than catecholamines</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 what doses does the selectivity of a drug to activate certain receptors decline?

    <p>As the dose increases</p> Signup and view all the answers

    What responses can be elicited by the activation of alpha-1 receptors?

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

    Which enzymes are responsible for the quick metabolism of catecholamines?

    <p>Monoamine oxidase [MAO] and catechol-O-methyltransferase [COMT]</p> Signup and view all the answers

    What distinguishes indirect agonists from direct agonists in terms of their mechanism of action?

    <p>Direct agonists work on receptor binding, while indirect agonists work by promoting norepinephrine release.</p> Signup and view all the answers

    What chemical groups characterize catecholamines?

    <p>Catechol and amine groups</p> Signup and view all the answers

    Why can catecholamines not be used orally?

    <p>Because they are quickly metabolized by enzymes and have a brief duration of action</p> Signup and view all the answers

    What is the defining characteristic of noncatecholamines in relation to the blood-brain barrier?

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

    What is the role of adrenergic agonists in activating adrenergic receptors?

    <p>Directly working on receptor binding</p> Signup and view all the answers

    What distinguishes catacholamines from noncatacholamines?

    <p>Catacholamines have a shorter duration of action than noncatacholamines</p> Signup and view all the answers

    Which group of drugs includes dopamine, epinephrine, isoproterenol, and ephedrine?

    <p>Indirect agonists</p> Signup and view all the answers

    What happens to catecholamines due to their chemistry?

    <p>They rapidly metabolize and cannot be used orally</p> Signup and view all the answers

    What is the role of noncatecholamines in relation to the blood-brain barrier?

    <p>They are unable to cross the blood-brain barrier like catecholamines</p> Signup and view all the answers

    What differentiates catecholamines from noncatecholamines in terms of oral use?

    <p>Catecholamines can be taken orally while noncatecholamines cannot</p> Signup and view all the answers

    What is the defining characteristic of adrenergic agonists known as sympathomimetics?

    <p>Their effects are similar to sympathetic nervous system activation due to using the same receptors</p> Signup and view all the answers

    What distinguishes catacholamines from noncatacholamines?

    <p>Availability for oral use, duration of action, and ability to act in the central nervous system</p> Signup and view all the answers

    What is the common structural feature of all catecholamines?

    <p>Hydroxyl groups on two adjacent carbons of a benzene ring</p> Signup and view all the answers

    Which enzyme is responsible for the rapid metabolism of catacholamines?

    <p>Catechol-O-methyltransferase [COMT]</p> Signup and view all the answers

    Why can't catacholamines be used orally?

    <p>They are rapidly metabolized by monoamine oxidase [MAO] and catechol-O-methyltransferase [COMT]</p> Signup and view all the answers

    Which class of adrenergic agonists includes dopamine and epinephrine?

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

    What distinguishes indirect agonists from direct agonists?

    <p>Mechanism of receptor activation</p> Signup and view all the answers

    What is the common mechanism of action for indirect agonists?

    <p>Promotion of norepinephrine release, blockade of norepinephrine re uptake, and inhibition of norepinephrine inactivation</p> Signup and view all the answers

    Why do catacholamines have a brief duration of action?

    <p>Rapid metabolism by monoamine oxidase [MAO] and catechol-O-methyltransferase [COMT]</p> Signup and view all the answers

    What prevents catacholamines from crossing the blood-brain barrier?

    <p>The presence of efflux transporters</p> Signup and view all the answers

    What makes noncatacholamines different from catecholamines?

    <p>Their ability to be used orally and duration of action</p> Signup and view all the answers

    What is the primary mechanism through which noncatacholamines exert their effects?

    <p>Inhibition of norepinephrine inactivation</p> Signup and view all the answers

    Why are noncatecholamines able to act in the central nervous system unlike catecholamines?

    <p>They are not susceptible to metabolism by hepatic enzymes</p> Signup and view all the answers

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