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Questions and Answers
What is the reason for catecholamine-containing solutions to turn pink or brown over time?
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?
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?
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?
What is the main adverse effect of alpha-1 receptor activation?
Which receptor activation is associated with reduction of sympathetic outflow to the heart and blood vessels?
Which receptor activation is associated with reduction of sympathetic outflow to the heart and blood vessels?
What effect does overstimulation of B1 receptors have on the heart?
What effect does overstimulation of B1 receptors have on the heart?
What is the therapeutic application of B2 receptor activation in the uterus?
What is the therapeutic application of B2 receptor activation in the uterus?
What is the adverse effect of B2 receptor activation in diabetics?
What is the adverse effect of B2 receptor activation in diabetics?
What is the primary effect of dopamine receptor activation in the kidneys?
What is the primary effect of dopamine receptor activation in the kidneys?
Which receptor activation stimulates the heart rate due to beta-1 activation?
Which receptor activation stimulates the heart rate due to beta-1 activation?
What is the primary effect of B1 receptor activation?
What is the primary effect of B1 receptor activation?
Why are noncatecholamines considerably less polar than catecholamines?
Why are noncatecholamines considerably less polar than catecholamines?
Which type of adrenergic agonist works by promoting norepinephrine release, blocking norepinephrine reuptake, and inhibiting norepinephrine inactivation?
Which type of adrenergic agonist works by promoting norepinephrine release, blocking norepinephrine reuptake, and inhibiting norepinephrine inactivation?
Why are adrenergic agonists often referred to as sympathomimetics?
Why are adrenergic agonists often referred to as sympathomimetics?
Which enzyme is responsible for the metabolism of catecholamines?
Which enzyme is responsible for the metabolism of catecholamines?
What prevents catecholamines from crossing the blood-brain barrier?
What prevents catecholamines from crossing the blood-brain barrier?
Which of the following is a structural component common to all catecholamines?
Which of the following is a structural component common to all catecholamines?
What is the main difference between catecholamines and noncatecholamines in terms of their oral use?
What is the main difference between catecholamines and noncatecholamines in terms of their oral use?
What is the mechanism of action of direct adrenergic agonists?
What is the mechanism of action of direct adrenergic agonists?
Why are noncatecholamines suitable for oral use compared to catecholamines?
Why are noncatecholamines suitable for oral use compared to catecholamines?
What is the significance of the amine component in catecholamines?
What is the significance of the amine component in catecholamines?
How do indirect adrenergic agonists exert their effects?
How do indirect adrenergic agonists exert their effects?
What distinguishes the two classes of adrenergic agonists, catecholamines and noncatecholamines?
What distinguishes the two classes of adrenergic agonists, catecholamines and noncatecholamines?
What is meant by a catechol group in catecholamines?
What is meant by a catechol group in catecholamines?
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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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